Stella Valenzuela undertook her PhD studies in cell and molecular biology [identifying novel genes – CLIC1 and MIC-1 - from activated macrophage cells] at the Centre for Immunology (CFI), St Vincent’s Hospital Sydney, obtaining her PhD from the University of NSW in 1998. Prior to this she had worked in the commercial sector, in the biotechnology companies Australian Monoclonal Development Pty Ltd and Cellabs Pty Ltd in research and development of monoclonal antibody technologies for research and diagnostic purposes.
In 2001 she joined the University of Technology, Key Centre for Health Technologies [cellular responses to mobile phone frequencies]. She is currently the Associate Head of School (Research) in the School of Life Sciences, UTS and the Director of the IDEAL Hub an ARC Industrial Transformation Research Hub.
Prof Valenzuela is a member of the Institute for Biomedical Materials and Devices at UTS. She leads bionanotechnology research on the therapeutic and diagnostic application of gold nanoparticles. She also works in collaboration with her industry partners Surgical Diagnostics Pty Ltd and Biotics Pty Ltd. developing diagnostic and biosensor devices that incorporate ion channel proteins with tethered membrane technologies.
Australian Society for Biophysics: 2005 to present
Australian Research Council Nanotechnology Network (ARCNN): 2007 to present
Can supervise: YES
Stella Valenzuela was awarded her PhD in 1998, and has extensive research experience in the field of cell biology, ion channels and membrane-associated proteins. She was the first to identify and characterise the protein NCC27 (now referred to as CLIC1) following the screening of a subtraction cDNA library for novel genes involved in macrophage activation. Her work demonstrated that CLIC1 was a novel nuclear chloride ion channel protein, published in the Journal of Biological Chemistry (1997). Her project also resulted in identification of a novel cytokine, MIC-1, published in PNAS, 1997. Since then she has demonstrated that CLIC1 was ubiquitously expressed in humans and involved in regulation of the cell cycle (J Physiol, 2000). This was followed by determination of the crystal structure of the soluble form of CLIC1 at 1.4 Å resolution, in collaboration with Prof Paul Curmi's team (JBC, 2001).
Most recently, her research team have demonstrated for the first time that members of the CLIC family have oxidoreductase enzymatic activity, in addition to being ion channels (PLOS ONE 2015 & Nature Communications 2017). Her group are also leading studies into the regulation of CLIC proteins by sterols. This work is applying tethered membrane technologies in collaboration with her industry partner, Surgical Diagnostics P/L along with neutron and X-ray reflectometry studies in collaboration with Dr Holt, at the BRAGG Institute, ANSTO.
Prof Valenzuela is currently Director of the IDEAL Research Hub, funded by the Australian Research Council. The IDEAL Hub brings together academic researchers and industry partners to focus on improving the sensitivity, selectivity, speed and cost-effectiveness of detecting at low levels in order to develop the next generation of diagnostic and testing devices.
Prof Valenzuela is recognized as one of the University’s leading Nanobiotechnology researchers. Her work with gold nanoparticles has potential application in the treatment of chronic inflammatory diseases by targeting and regulating macrophage cells. Working with Professor Cortie from the Institute of Nanoscale Technologies at UTS, they successfully demonstrated the first selective targeting and killing of disease-causing protozoans by photothermal treatment with antibody conjugated gold nanoparticles. Her more recent work with Dr Hui Chen has demonstrated a role for gold nanoparticles in the regulation of obesity and metabolic disorders (PLOS ONE, 2013 and Journal of Nanobiotechnology, 2018) .
Current Lab Group Members:
Ms Hala Ali
Ms Claudia D'Amario
Mr Daniel Turkewitz
Ms Amani Alghalayini (Joint-supervisor, Dr Charles Cranfield; SoLS, UTS)
- Mr Kerem Bray (primary supervisor, Prof Igor Aharonovich - MAPS, UTS)
- Ms Yinghui (Yvonne) Chen (primary supervisor, Prof Dayong Jin - MAPS, UTS)
- Ms Kirsty Milner (primary supervisor, A/Prof Andy Leigh, SOLS, UTS)
Ms Leonie Herson
Ms Saba Moghaddasi
- Ms Camilla Gazzana (primary supervisor, Prof Michael Cortie)
Dr Kristhanthi Jayasundera & Dr Hedayat Islam
Professor Valenzuela co-ordinates the subject Bionanotechnology (91140).
She teaches into various subjects/course including Cell Biology and Genetics, Neuroscience, Physiology/Human Movement and Biotechnology.
Chen, Y, D'Amario, C, Gee, A, Duong, HTT, Shimoni, O & Valenzuela, SM 2020, 'Dispersion stability and biocompatibility of four ligand-exchanged NaYF4: Yb, Er upconversion nanoparticles.', Acta Biomaterialia, vol. 102, pp. 384-393.View/Download from: Publisher's site
Surface modification to obtain high dispersion stability and biocompatibility is a key factor for bio-application of upconversion nanoparticles (UCNPs). A systematic study of UCNPs modified with four hydrophilic molecules separately, comparing their dispersion stability in biological buffers and cellular biocompatibility is reported here. The results show that carboxyl-functionalized UCNPs (modified by 3,4-dihydrocinnamic acid (DHCA) or poly(monoacryloxyethyl phosphate (MAEP)) with negative surface charge have superior even-distribution in biological buffers compared to amino-functionalized UCNPs (modified by (aminomethyl)phosphonic (AMPA) or (3-Aminopropyl)triethoxysilane (APTES)) with positive surface charge. Subsequent investigation of cellular interactions revealed high levels of non-targeted cellular uptake of the particles modified with either of the three small molecules (AMPA, APTES, DHCA) and high levels of cytotoxicity when used at high concentrations. The particles were seen to be trapped as particle-aggregates within the cellular cytoplasm, leading to reduced cell viability and cell proliferation, along with dysregulation of the cell cycle as assessed by DNA content measurements. The dramatically reduced proportion of cells in G1 phase and the slightly increased proportion in G2 phase indicates inhibition of M phase, and the appearance of sub-G1 phase reflects cell necrosis. In contrast, MAEP-modified UCNPs are bio-friendly with increased dispersion stability in biological buffers, are non-cytotoxic, with negligible levels of non-specific cellular uptake and no effect on the cell cycle at both low and high concentrations. MAEP-modified UCNPs were further functionalized with streptavidin for intracellular microtubule imaging, and showed clear cytoskeletal structures via their upconversion luminescence. STATEMENT OF SIGNIFICANCE: Upconversion nanoparticles (UCNP) are an exciting potential nanomaterial for bio-applications. Their anti-Stokes luminescence...
Alghalayini, A, Jiang, L, Gu, X, Yeoh, GH, Cranfield, CG, Timchenko, V, Cornell, BA & Valenzuela, SM 2020, 'Real-time monitoring of heat transfer between gold nanoparticles and tethered bilayer lipid membranes', BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES, vol. 1862, no. 9.View/Download from: Publisher's site
Hossain, KR, Turkewitz, DR, Holt, SA, Herson, L, Brown, LJ, Cornell, BA, Curmi, PMG & Valenzuela, SM 2019, 'A conserved GXXXG motif in the transmembrane domain of CLIC proteins is essential for their cholesterol-dependant membrane interaction.', Biochimica et biophysica acta. General subjects, vol. 1863, no. 8, pp. 1243-1253.View/Download from: Publisher's site
BACKGROUND:Sterols have been reported to modulate conformation and hence the function of several membrane proteins. One such group is the Chloride Intracellular Ion Channel (CLIC) family of proteins. The CLIC protein family consists of six evolutionarily conserved protein members in vertebrates. These proteins exist as both monomeric soluble proteins and as membrane bound proteins. To date, the structure of their membrane-bound form remains unknown. In addition to several studies indicating cellular redox environment and pH as facilitators of CLIC1 insertion into membranes, we have also demonstrated that the spontaneous membrane insertion of CLIC1 is regulated by membrane cholesterol. METHOD:We have performed Langmuir-film, Impedance Spectroscopy and Molecular Docking Simulations to study the role of this GXXXG motif in CLIC1 interaction with cholesterol. RESULTS:Unlike CLIC1-wild-type protein, the G18A and G22A mutants, that form part of the GXXXG motif, showed much slower initial kinetics and lower ion channel activity compared to the native protein. This difference can be attributed to the significantly reduced membrane interaction and insertion rate of the mutant proteins and/or slower formation of the final membrane configuration of the mutant proteins once in the membrane. CONCLUSION:In this study, our findings uncover the identification of a GXXXG motif in CLIC1, which likely serves as the cholesterol-binding domain, that facilitates the protein's membrane interaction and insertion. Furthermore, we were able to postulate a model by which CLIC1 can autonomously insert into membranes to form functional ion channels. GENERAL SIGNIFICANCE:Members of the CLIC family of proteins demonstrate unusual structural and dual functional properties - as ion channels and enzymes. Elucidating how the CLIC proteins' interact with membranes, thus allowing them to switch between their soluble and membrane form, will provide key information as to a mechanism of moonlighting ac...
Chen, H, Ng, JPM, Bishop, DP, Milthorpe, BK & Valenzuela, SM 2018, 'Gold nanoparticles as cell regulators: beneficial effects of gold nanoparticles on the metabolic profile of mice with pre-existing obesity', JOURNAL OF NANOBIOTECHNOLOGY, vol. 16.View/Download from: Publisher's site
Chen, H, Ng, JPM, Tan, Y, McGrath, K, Bishop, DP, Oliver, B, Chan, YL, Cortie, MB, Milthorpe, BK & Valenzuela, SM 2018, 'Gold nanoparticles improve metabolic profile of mice fed a high-fat diet', JOURNAL OF NANOBIOTECHNOLOGY, vol. 16.View/Download from: Publisher's site
Bray, K, Cheung, L, Hossain, KR, Aharonovich, I, Valenzuela, SM & Shimoni, O 2018, 'Versatile multicolor nanodiamond probes for intracellular imaging and targeted labeling', JOURNAL OF MATERIALS CHEMISTRY B, vol. 6, no. 19, pp. 3078-3084.View/Download from: Publisher's site
Chen, Y, Duong, HTT, Wen, S, Mi, C, Zhou, Y, Shimoni, O, Valenzuela, SM & Jin, D 2018, 'Exonuclease III-Assisted Upconversion Resonance Energy Transfer in a Wash-Free Suspension DNA Assay.', Analytical Chemistry, vol. 90, no. 1, pp. 663-668.View/Download from: Publisher's site
Sensitivity is the key in optical detection of low-abundant analytes, such as circulating RNA or DNA. The enzyme Exonuclease III (Exo III) is a useful tool in this regard; its ability to recycle target DNA molecules results in markedly improved detection sensitivity. Lower limits of detection may be further achieved if the detection background of autofluorescence can be removed. Here we report an ultrasensitive and specific method to quantify trace amounts of DNA analytes in a wash-free suspension assay. In the presence of target DNA, the Exo III recycles the target DNA by selectively digesting the dye-tagged sequence-matched probe DNA strand only, so that the amount of free dye removed from the probe DNA is proportional to the number of target DNAs. Remaining intact probe DNAs are then bound onto upconversion nanoparticles (energy donor), which allows for upconversion luminescence resonance energy transfer (LRET) that can be used to quantify the difference between the free dye and tagged dye (energy acceptor). This scheme simply avoids both autofluorescence under infrared excitation and many tedious washing steps, as the free dye molecules are physically located away from the nanoparticle surface, and as such they remain "dark" in suspension. Compared to alternative approaches requiring enzyme-assisted amplification on the nanoparticle surface, introduction of probe DNAs onto nanoparticles only after DNA hybridization and signal amplification steps effectively avoids steric hindrance. Via this approach, we have achieved a detection limit of 15 pM in LRET assays of human immunodeficiency viral DNA.
Hernandez-Fernaud, JR, Ruengeler, E, Casazza, A, Neilson, LJ, Pulleine, E, Santi, A, Ismail, S, Lilla, S, Dhayade, S, MacPherson, IR, McNeish, I, Ennis, D, Ali, H, Kugeratski, FG, Al Khamici, H, van den Biggelaar, M, van den Berghe, PVE, Cloix, C, McDonald, L, Millan, D, Hoyle, A, Kuchnio, A, Carmeliet, P, Valenzuela, SM, Blyth, K, Yin, H, Mazzone, M, Norman, JC & Zanivan, S 2017, 'Secreted CLIC3 drives cancer progression through its glutathione-dependent oxidoreductase activity.', Nature Communications, vol. 8, pp. 1-17.View/Download from: Publisher's site
The secretome of cancer and stromal cells generates a microenvironment that contributes to tumour cell invasion and angiogenesis. Here we compare the secretome of human mammary normal and cancer-associated fibroblasts (CAFs). We discover that the chloride intracellular channel protein 3 (CLIC3) is an abundant component of the CAF secretome. Secreted CLIC3 promotes invasive behaviour of endothelial cells to drive angiogenesis and increases invasiveness of cancer cells both in vivo and in 3D cell culture models, and this requires active transglutaminase-2 (TGM2). CLIC3 acts as a glutathione-dependent oxidoreductase that reduces TGM2 and regulates TGM2 binding to its cofactors. Finally, CLIC3 is also secreted by cancer cells, is abundant in the stromal and tumour compartments of aggressive ovarian cancers and its levels correlate with poor clinical outcome. This work reveals a previously undescribed invasive mechanism whereby the secretion of a glutathione-dependent oxidoreductase drives angiogenesis and cancer progression by promoting TGM2-dependent invasion.
Hossain, KR, Holt, SA, Le Brun, AP, Al Khamici, H & Valenzuela, SM 2017, 'X-ray and Neutron Reflectivity Study Shows That CLIC1 Undergoes Cholesterol-Dependent Structural Reorganization in Lipid Monolayers.', Langmuir, vol. 33, no. 43, pp. 12497-12509.View/Download from: Publisher's site
CLIC1 belongs to the ubiquitous family of chloride intracellular ion channel proteins that are evolutionarily conserved across species. The CLICs are unusual in that they exist mainly as soluble proteins but possess the intriguing property of spontaneous conversion from the soluble to an integral membrane-bound form. This conversion is regulated by the membrane lipid composition, especially by cholesterol, together with external factors such as oxidation and pH. However, the precise physiological mechanism regulating CLIC1 membrane insertion is currently unknown. In this study, X-ray and neutron reflectivity experiments were performed to study the interaction of CLIC1 with different phospholipid monolayers prepared using POPC, POPE, or POPS with and without cholesterol in order to better understand the regulatory role of cholesterol in CLIC1 membrane insertion. Our findings demonstrate for the first time two different structural orientations of CLIC1 within phospholipid monolayers, dependent upon the absence or presence of cholesterol. In phospholipid monolayers devoid of cholesterol, CLIC1 was unable to insert into the lipid acyl chain region. However, in the presence of cholesterol, CLIC1 showed significant insertion within the phospholipid acyl chains occupying an area per protein molecule of 6-7 nm(2) with a total CLIC1 thickness ranging from ∼50 to 56 Å across the entire monolayer. Our data strongly suggests that cholesterol not only facilitates the initial docking or binding of CLIC1 to the membrane but also promotes deeper penetration of CLIC1 into the hydrophobic tails of the lipid monolayer.
Al Khamici, H, Hossain, KR, Cornell, BA & Valenzuela, SM 2016, 'Investigating Sterol and Redox Regulation of the Ion Channel Activity of CLIC1 Using Tethered Bilayer Membranes.', Membranes, vol. 6, no. 4, pp. 1-13.View/Download from: Publisher's site
The Chloride Intracellular Ion Channel (CLIC) family consists of six conserved proteins in humans. These are a group of enigmatic proteins, which adopt both a soluble and membrane bound form. CLIC1 was found to be a metamorphic protein, where under specific environmental triggers it adopts more than one stable reversible soluble structural conformation. CLIC1 was found to spontaneously insert into cell membranes and form chloride ion channels. However, factors that control the structural transition of CLIC1 from being an aqueous soluble protein into a membrane bound protein have yet to be adequately described. Using tethered bilayer lipid membranes and electrical impedance spectroscopy system, herein we demonstrate that CLIC1 ion channel activity is dependent on the type and concentration of sterols in bilayer membranes. These findings suggest that membrane sterols play an essential role in CLIC1's acrobatic switching from a globular soluble form to an integral membrane form, promoting greater ion channel conductance in membranes. What remains unclear is the precise nature of this regulation involving membrane sterols and ultimately determining CLIC1's membrane structure and function as an ion channel. Furthermore, our impedance spectroscopy results obtained using CLIC1 mutants, suggest that the residue Cys24 is not essential for CLIC1's ion channel function. However Cys24 does appear important for optimal ion channel activity. We also observe differences in conductance between CLIC1 reduced and oxidized forms when added to our tethered membranes. Therefore, we conclude that both membrane sterols and redox play a role in the ion channel activity of CLIC1.
Cranfield, CG, Berry, T, Holt, SA, Hossain, KR, Le Brun, AP, Carne, S, Al Khamici, H, Coster, H, Valenzuela, SM & Cornell, B 2016, 'Evidence of the Key Role of H3O+ in Phospholipid Membrane Morphology', LANGMUIR, vol. 32, no. 41, pp. 10725-10734.View/Download from: Publisher's site
Hossain, KR, Al Khamici, H, Holt, SA & Valenzuela, SM 2016, 'Cholesterol Promotes Interaction of the Protein CLIC1 with Phospholipid Monolayers at the Air-Water Interface.', Membranes, vol. 6, no. 1, pp. 1-13.View/Download from: Publisher's site
CLIC1 is a Chloride Intracellular Ion Channel protein that exists either in a soluble state in the cytoplasm or as a membrane bound protein. Members of the CLIC family are largely soluble proteins that possess the intriguing property of spontaneous insertion into phospholipid bilayers to form integral membrane ion channels. The regulatory role of cholesterol in the ion-channel activity of CLIC1 in tethered lipid bilayers was previously assessed using impedance spectroscopy. Here we extend this investigation by evaluating the influence of cholesterol on the spontaneous membrane insertion of CLIC1 into Langmuir film monolayers prepared using 1-palmitoyl-2-oleoylphosphatidylcholine, 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-ethanolamine and 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-L-serine alone or in combination with cholesterol. The spontaneous membrane insertion of CLIC1 was shown to be dependent on the presence of cholesterol in the membrane. Furthermore, pre-incubation of CLIC1 with cholesterol prior to its addition to the Langmuir film, showed no membrane insertion even in monolayers containing cholesterol, suggesting the formation of a CLIC1-cholesterol pre-complex. Our results therefore suggest that CLIC1 membrane interaction involves CLIC1 binding to cholesterol located in the membrane for its initial docking followed by insertion. Subsequent structural rearrangements of the protein would likely also be required along with oligomerisation to form functional ion channels.
Yeoh, GH, Gu, X, Timchenko, V, Valenzuela, SM & Cornell, BA 2016, 'High order accurate dual-phase-lag numerical model for microscopic heating in multiple domains', INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER, vol. 78, pp. 21-28.View/Download from: Publisher's site
Al Khamici, H, Brown, LJ, Hossain, KR, Hudson, AL, Sinclair-Burton, AA, Jane, PMN, Daniel, EL, Hare, JE, Cornell, BA, Curmi, PMG, Davey, MW & Valenzuela, SM 2015, 'Members of the Chloride Intracellular Ion Channel Protein Family Demonstrate Glutaredoxin-Like Enzymatic Activity', PLOS ONE, vol. 10, no. 1.View/Download from: Publisher's site
Valenzuela, SM, Jiang, L, Curmi, PMG, Phang, JM, Yu, J, Harrop, SJ, Sokolova, AV, Duff, AP, Wilk, KE, Alkhamici, H, Breit, SN & Brown, LJ 2014, 'CLIC proteins, ezrin, radixin, moesin and the coupling of membranes to the actin cytoskeleton: A smoking gun?', Biochimica et Biophysica Acta - Biomembranes, vol. 1838, no. 2, pp. 643-657.View/Download from: Publisher's site
The CLIC proteins are a highly conserved family of metazoan proteins with the unusual ability to adopt both soluble and integral membrane forms. The physiological functions of CLIC proteins may include enzymatic activity in the soluble form and anion channel activity in the integral membrane form. CLIC proteins are associated with the ERM proteins: ezrin, radixin and moesin. ERM proteins act as cross-linkers between membranes and the cortical actin cytoskeleton. Both CLIC and ERM proteins are controlled by Rho family small GTPases. CLIC proteins, ERM and Rho GTPases act in a concerted manner to control active membrane processes including the maintenance of microvillar structures, phagocytosis and vesicle trafficking. All of these processes involve the interaction of membranes with the underlying cortical actin cytoskeleton. The relationships between Rho GTPases, CLIC proteins, ERM proteins and the membrane:actin cytoskeleton interface are reviewed. Speculative models are proposed involving the formation of localised multi-protein complexes on the membrane surface that assemble via multiple weak interactions. This article is part of a Special Issue entitled: Reciprocal influences between cell cytoskeleton and membrane channels, receptors and transporters
Yepuri, NR, Holt, SA, Moraes, G, Holden, PJ, Hossain, KR, Valenzuela, SM, James, M & Darwish, TA 2014, 'Stereoselective synthesis of perdeuterated phytanic acid, its phospholipid derivatives and their formation into lipid model membranes for neutron reflectivity studies', CHEMISTRY AND PHYSICS OF LIPIDS, vol. 183, pp. 22-33.View/Download from: Publisher's site
Chou, J, Valenzuela, S, Green, DW, Kohan, L, Milthorpe, B, Otsuka, M & Ben-Nissan, B 2014, 'Antibiotic delivery potential of nano and micro porous marine structures derived ß-TCP spheres for medical applications', Nanomedicine, vol. 1, pp. 1-9.View/Download from: Publisher's site
This study gives a detailed evaluation of the antibiotic potential of a marine structure-based new
drug delivery system produced by hydrothermally converting foraminifera exoskeletons to b-tricalcium
phosphate (b-TCP) to treat clinical strain Staphylococcus aureus (MW2). Materials & methods: Foraminifera
precursor materials were hydrothermally converted at 250°C for 48 h to produce b-TCP and loaded with
gentamicin sulfate by adsorption for 24 h. The physicochemical properties of the material were characterized
by scanning electron microscopy, powder x-ray diffraction and for pore size distribution profiles. The
antibacterial efficacy of the system was tested for inhibition of S. aureus growth and in vitro cellular
behavior were tested with human osteoblast cells (MG63) for cell viability. Discussion: Pore size distribution
profiles showed that the structure allows the uniform distribution of nanopores of 1.5 nm and micropores
of approximately 5 μm. The in vitro release profile indicates an initial burst release of 5% of total
incorporated gentamicin. A time-delayed antibacterial efficacy test was designed to introduce the bacteria
at predetermined time intervals from 0 to 60 min and showed that gentamicin prevents S. aureus grown
in the same culture within 30 min, with no evidence of bacterial regrowth within 24 h. Human osteoblast
cell (MG63) studies showed no detrimental effect on cell viability. Conclusion: In the light of these results
nano- and micro-pores
Chou, J, Valenzuela, SM, Santos, J, Bishop, D, Milthorpe, B, Green, DW, Otsuka, M & Ben-Nissan, B 2014, 'Strontium- and magnesium-enriched biomimetic beta-TCP macrospheres with potential for bone tissue morphogenesis', JOURNAL OF TISSUE ENGINEERING AND REGENERATIVE MEDICINE, vol. 8, no. 10, pp. 771-778.View/Download from: Publisher's site
Chen, H, Dorrigan, A, Saad, S, Hare, DJ, Cortie, MB & Valenzuela, S 2013, 'In Vivo Study of Spherical Gold Nanoparticles: Inflammatory Effects and Distribution in Mice', PLoS One, vol. 8, no. 2, pp. 1-8.View/Download from: Publisher's site
Objectives Gold nanoparticles (AuNPs) of 21 nm have been previously well characterized in vitro for their capacity to target macrophages via active uptake. However, the short-term impact of such AuNPs on physiological systems, in particular resident macrophages located in fat tissue in vivo, is largely unknown. This project investigated the distribution, organ toxicity and changes in inflammatory cytokines within the adipose tissue after mice were exposed to AuNPs. Methods Male C57BL/6 mice were injected intraperitoneally (IP) with a single dose of AuNPs (7.85 µg AuNPs/g). Body weight and energy intake were recorded daily. Tissues were collected at 1 h, 24 h and 72 h post-injection to test for organ toxicity. AuNP distribution was examined using electron microscopy. Proinflammatory cytokine expression and macrophage number within the abdominal fat pad were determined using real-time PCR.
Jones, PM, Curmi, PMG, Valenzuela, SM & George, AM 2013, 'Computational Analysis of the Soluble Form of the Intracellular Chloride Ion Channel Protein CLIC1', BIOMED RESEARCH INTERNATIONAL, vol. 2013.View/Download from: Publisher's site
Valenzuela, S, Alkhamici, H, Brown, LJ, Almond, OC, Goodchild, SC, Carne, S, Curmi, PM, Holt, S & Cornell, BA 2013, 'Regulation Of The Membrane Insertion And Conductance Activity Of The Metamorphic Chloride Intracellular Channel Protein CLIC1 By Cholesterol', Plos One, vol. 8, no. 2, pp. 1-8.View/Download from: Publisher's site
The Chloride Intracellular ion channel protein CLIC1 has the ability to spontaneously insert into lipid membranes from a soluble, globular state. The precise mechanism of how this occurs and what regulates this insertion is still largely unknown, although factors such as pH and redox environment are known contributors. In the current study, we demonstrate that the presence and concentration of cholesterol in the membrane regulates the spontaneous insertion of CLIC1 into the membrane as well as its ion channel activity. The study employed pressure versus area change measurements of Langmuir lipid monolayer films; and impedance spectroscopy measurements using tethered bilayer membranes to monitor membrane conductance during and following the addition of CLIC1 protein. The observed cholesterol dependent behaviour of CLIC1 is highly reminiscent of the cholesterol-dependent-cytolysin family of bacterial pore-forming proteins, suggesting common regulatory mechanisms for spontaneous protein insertion into the membrane bilayer.
Cortie, MB, Al Hafed, E, Chen, H, Valenzuela, S, Ting, S, Sonvico, F & Milthorpe, BK 2013, 'Nanomedical research in Australia and New Zealand', Nanomedicine, vol. 8, no. 12, pp. 1999-2006.View/Download from: Publisher's site
Although Australia and New Zealand have a combined population of less than 30 million, they have an active and interlinked community of nanomedical researchers. This report provides a synopsis and update on this network with a view to identifying the main topics of interest and their likely future trajectories. In addition, our report may also serve to alert others to opportunities for joint projects. Australian and New Zealand researchers are engaged in most of the possible nanomedical topics, but the majority of interest is focused on drug and nucleic acid delivery using nanoparticles or nanoporous constructs. There are, however, smaller programs directed at hyperthermal therapy and radiotherapy, various kinds of diagnostic tests and regenerative technologies.
Chou, J, Ben-Nissan, B, Green, DD, Valenzuela, S & Kohan, L 2011, 'Targeting And Dissolution Characteristics Of Bone Forming And Antibacterial Drugs By Harnessing The Structure Of Microspherical Shells From Coral Beach Sand', Advanced Engineering Materials, vol. 13, no. 1-2, pp. 93-99.View/Download from: Publisher's site
Pharmaceutical drugs for the treatment of metabolic bone diseases lead to a number of side effects due to the their uncontrollable dispersion throughout the body.() Therefore, many groups directed their research to develop devices that are targeted to
Valenzuela, S, Berkahn, MB, Porkovich, A, Huynh, TG, Goyette, J, Martin, DK & Geczy, CL 2011, 'Soluble structure of CLIC and S100 proteins investigated by atomic force microscopy', Journal of Biomaterials and Nanobiotechnology, vol. 2, pp. 8-17.View/Download from: Publisher's site
The ability to visualise proteins in their native environment and discern information regarding stoichiometry is of critical importance when studying protein interactions and function. We have used liquid cell atomic force microscopy (AFM) to visualise proteins in their native state in buffer and have determined their molecular volumes. The human proteins S100A8, S100A9, S100A12 and CLIC1 were used in this investigation. The effect of oxidation on the protein structure of CLIC1 was also investigated and we found that CLIC1 multimerisation could be discerned by AFM, which supports similar findings by other methods. We have found good correlation between the molecular volumes measured by AFM and the calculated volumes of the individual proteins. This method allows for the study of single soluble proteins under physiological conditions and could potentially be extended to study the structure of these proteins when located within a membrane environment.
Windley, MJ, Escoubas, P, Valenzuela, S & Nicholson, GM 2011, 'A Novel Family of Insect-Selective Peptide Neurotoxins Targeting Insect Large-Conductance Calcium-Activated K(+) Channels Isolated from the Venom of the Theraphosid Spider Eucratoscelus constrictus', Molecular Pharmacology, vol. 80, no. 1, pp. 1-13.View/Download from: Publisher's site
Spider venoms are actively being investigated as sources of novel insecticidal agents for biopesticide engineering. After screening 37 theraphosid spider venoms, a family of three new "short-loop" inhibitory cystine knot insecticidal toxins (kappa-TRTX-Ec2a, kappa-TRTX-Ec2b, and kappa-TRTX-Ec2c) were isolated and characterized from the venom of the African tarantula Eucratoscelus constrictus. Whole-cell patch-clamp recordings from cockroach dorsal unpaired median neurons revealed that, despite significant sequence homology with other theraphosid toxins, these 29-residue peptides lacked activity on insect voltage-activated sodium and calcium channels. It is noteworthy that kappa-TRTX-Ec2 toxins were all found to be high-affinity blockers of insect large-conductance calcium-activated K+ (BKCa) channel currents with IC50 values of 3 to 25 nM. In addition, kappa-TRTX-Ec2a caused the inhibition of insect delayed-rectifier K+ currents, but only at significantly higher concentrations. kappa-TRTX-Ec2a and kappa-TRTX-Ec2b demonstrated insect-selective effects, whereas the homologous kappa-TRTX-Ec2c also resulted in neurotoxic signs in mice when injected intracerebroventricularly. Unlike other theraphosid toxins, kappa-TRTX-Ec2 toxins induce a voltage-independent channel block, and therefore, we propose that these toxins interact with the turret and/or loop region of the external entrance to the channel and do not project deeply into the pore of the channel. Furthermore, kappa-TRTX-Ec2a and kappa-TRTX-Ec2b differ from other theraphotoxins at the C terminus and positions 5 to 6, suggesting that these regions of the peptide contribute to the phyla selectivity and are involved in targeting BKCa channels. This study therefore establishes these toxins as tools for studying the role of BKCa channels in insects and lead compounds for the development of novel insecticides.
Littler, DR, Harrop, SJ, Goodchild, SC, Phang, JM, Mynott, AV, Jiang, L, Valenzuela, S, Mazzanti, M, Brown, LJ, Breit, S & Curmi, PM 2010, 'The enigma of the CLIC proteins: Ion channels, redox proteins, enzymes, scaffolding proteins?', FEB Letters, vol. 584, no. 10, pp. 2093-2101.
Chloride intracellular channel proteins (CLICs) are distinct from most ion channels in that they have both soluble and integral membrane forms. CLICs are highly conserved in chordates, with six vertebrate paralogues. CLIC-like proteins are found in other metazoans. CLICs form channels in artificial bilayers in a process favoured by oxidising conditions and low pH. They are structurally plastic, with CLIC1 adopting two distinct soluble conformations. Phylogenetic and structural data indicate that CLICs are likely to have enzymatic function. The physiological role of CLICs appears to be maintenance of intracellular membranes, which is associated with tubulogenesis but may involve other substructures.
Pissuwan, D, Cortie, CH, Valenzuela, S & Cortie, MB 2010, 'Functionalised gold nanoparticles for controlling pathogenic bacteria', Trends In Biotechnology, vol. 28, no. 4, pp. 207-213.View/Download from: Publisher's site
The incereasing number of bacterial strains that are resistant to available pharmaceutical compounds is a vital issue for public health. Innovative approaches will be required to improve the methids for both diagnosis and destruction of these organisms. Here we consider the possible role that can be plaued by technologies based on gold nanoparticles. Gold nanoparticles generally are considered to be biologically inert but can be engineered to possess chemical or photothermal functionality. A growing body of research is devoted to the potential use of these nanoparticles in the diagnosis and treatment of bacterial infections. The results are both promising and intriguing and suggest a range of new strategies io identiofy target or destrpy pathogenic organisms.
Qiu, M, Jiang, L, Matthaei, K, Schoenwaelder, S, Kuffner, T, Mangin, P, Joseph, J, Low, JA, Connor, DI, Valenzuela, S, Curmi, PM, Brown, L, Mahaut-smith, M, Jackson, S & Breit, SN 2010, 'Generation And Characterization Of Mice With Null Mutation Of The Chloride Intracellular Channel 1 Gene', Genesis, vol. 48, no. 2, pp. 127-136.View/Download from: Publisher's site
CLIC1 belongs to a family of highly conserved and widely expressed intracellular chloride ion channel proteins existing in both soluble and membrane integrated forms.
Qiu, MR, Jiang, L, Matthaei, KI, Schoenwaelder, SM, Kuffner, T, Mangin, P, Joseph, JE, Low, J, Connor, D, Valenzuela, SM, Curmi, PMG, Brown, LJ, Mahaut-Smith, M, Jackson, SP & Breit, SN 2010, 'Generation and Characterization of Mice With Null Mutation of the Chloride Intracellular Channel 1 Gene', GENESIS, vol. 48, no. 2, pp. 127-136.View/Download from: Publisher's site
Ting, HJ, Haas, MR, Valenzuela, S & Martin, DK 2010, 'Terminating polyelectrolyte in multilayer films influences growth and morphology of adhering cells', Iet Nanobiotechnology, vol. 4, no. 3, pp. 77-90.View/Download from: Publisher's site
Polyelectrolyte films of anionic poly(sodium 4-styrenesulphonate) (PSS) and cationic poly (allylamine hydrochloride) (PAH) were constructed using layer-by-layer assembly. The authors examined the cytocompatibility of these films for future use in nanobiotechnology applications. Cell lines HEK-293 and 3T3-L1 were cultured on these films and the initial attachment, adhesion, proliferation and cytotoxicity of the cells were measured using a propidium iodide assay. The morphology and spread of the cells were measured by phase-contrast microscopy. The actin cytoskeleton was observed using fluorescent microscopy. Neither the PAH-terminated nor the PSS-terminated polyelectrolyte films were cytotoxic. The PAH-terminated polyelectrolyte films improved the initial attachment and subsequent adhesion of the cells, in addition to enhancing the production of extracellular matrix and the modelling of the actin filaments. The PSS-terminated film enhanced the proliferation of the cells compared to the PAH-terminated film. That was despite the cell cycle, the spreading or the cytotoxicity of both cell types being similar for either the PSS-terminated surfaces or the PAH-terminated surfaces. Cell behaviour can be modulated by the final surface charge of the polyelectrolyte film and the results are useful in guiding the choice of substrates and/or coatings for potential biomedical applications (e.g. implants) as well as cell biology research.
Battle, AR, Valenzuela, S, Mechler, A, Nichols, R, Praporski, S, Di Maio, I, Islam, H, Girard-Egrot, AP, Cornell, BA, Prashar, J, Caruso, F, Martin, LL & Martin, DK 2009, 'Novel engineered ion channel provides controllable ion permability for polyelectrolyte microcapsules coated with a lipid membrane', Advanced Functional Materials, vol. 19, pp. 201-208.View/Download from: Publisher's site
The development of nanostructured microcapsules based on a biomimetic lipid bilayer membrane (BLM) coating of poly(SODIUM STYRENESUFONATE) (pss) /POLY(ALLYLAMINE HYDROCHLORIDE) (pah) POLYELECTROLYTE HOLLOW MICROCAPSULES IS REPORTED
Rod-shaped gold nanoparticles ('nanorods') have recently attracted widespread attention due to their unique optical properties and facile synthesis. In particular, they can support a longtudinal surface plasmon, which results in suspensions of themhaving a strong extinction peak in the upper visible or near-infrared parts of the spectrum. The position of this peak can be readily tuned by controlling the shape of the rods. In addition, the surface of the nanorods can be functionalised by a very wide variety of molecules. This has led to interest in their use as selctive biomarkers in biodiagnostics or for selective targeting in photothermal therapeutics. Here we review the recent advances in the use of gold nanoparticles in these applications. additionally the information available regarding their biocompatibility in discussed.
Pissuwan, D, Valenzuela, S, Miller, CM, Killingsworth, MC & Cortie, MB 2009, 'Destruction and Control of Toxoplasma gondii Tachyzoites Using Gold Nanosphere / Antibody Conjugates', Small, vol. 5, no. 9, pp. 1030-1034.View/Download from: Publisher's site
The protozoan parasiteToxoplasma gondii can be selectively targeted and photothermally destroyed by gold nanosphere/antibody conjugates (see image). The optical response of the nanospheres within the tissue window is shifted and enhanced by aggregation. Attachment of the conjugates alone, even without plasmonic heating, lowers the infectivity of the organism.
Gunning, SJ, Maggio, FJ, Windley, MJ, Valenzuela, S, King, GF & Nicholson, GM 2008, 'The Janus-faced atracotoxins are specific blockers of invertebrate K(Ca) channels', FEBS Journal, vol. 275, no. 16, pp. 4045-4059.View/Download from: Publisher's site
The Janus-faced atracotoxins are a unique family of excitatory peptide toxins that contain a rare vicinal disulfide bridge. Although lethal to a wide range of invertebrates, their molecular target has remained enigmatic for almost a decade. We demonstrate here that these toxins are selective, high-affinity blockers of invertebrate calcium activated K+ (KCa) channels. J-ACTX-Hv1c, the prototypic member of this toxin family, selectively blocked KCa channels in cockroach unpaired dorsal median neurons with an IC50 of 2 nM, but it did not significantly affect a wide range of other voltage activated potassium (KV), calcium (CaV), or sodium (NaV) channel subtypes. J ACTX-Hv1c blocked heterologously expressed cockroach BKCa (pSlo) channels without a significant shift in the voltage-dependence of activation. However, the block was voltage-dependent, indicating that the toxin likely acts as a pore blocker rather than a gating modifier. The molecular basis of the insect selectivity of J-ACTX-Hv1c was established by its failure to significantly inhibit mouse mSlo currents (IC50 ~10 Î¼M) and its lack of activity on rat dorsal root ganglion neuron IK(Ca). This study establishes the Janus-faced atracotoxins as valuable tools for the study of invertebrate KCa channels and suggests that KCa channels might be a potential insecticide target.
Titanium nitride thin films are widely used in biomedical implants because of thier biocompatibility, good mechanical properties and high corrosion resistance. Titanium nitride (TiN) thin films on silicon and glass substrates were prepared using a dc megnetron sputtering system under condition of systematically varying the nitrogen pressure and titanium megnetron power.
Lewis, KC, Valenzuela, S & Ben-Nissan, B 2008, 'Changes in the Activity of Osteoblast Like Cells with Sol-Gel Derived Hydroxyapatite and Zirconia Nanocoatings', Key Engineering Materials, vol. 361-363, no. 1, pp. 633-636.
When producing implant materials, achievement of optimal bioactivity and biocompatibility are essential. Nanocoatings can provide an efficient cost effective way to alter the interactions of the implant material with its destined host environment. Nanocoatings of sol-gel derived carbonated hydroxyapatite (HAp) and zirconia were produced in this study. The surfaces were characterised by Fourier transform infrared spectroscopy (FTIR) and light microscopy. Cell adhesion, proliferation and viability, as well as expression of alkaline phosphatase (ALP is an indicator of bone formation) were assessed as indicators of biocompatibility. Our results have shown that sol-gel derived nano crystalline HAp acts as an ideal surface for implant coatings.
Bobryshev, YV, Killingsworth, MC, Huynh, TG, Lord, RS, Grabs, AJ & Valenzuela, S 2007, 'Are calcifying matrix vesicles in atherosclerotic lesions of cellular origin?', Basic Research in Cardiology, vol. 102, no. 2, pp. 133-143.View/Download from: Publisher's site
Over recent years, the role of matrix vesicles in the initial stages of arterial calcification has been recognised. Matrix calcifying vesicles have been isolated from atherosclerotic arteries and the biochemical composition of calcified vesicles has been studied. No Studies have yet been carried out to examine the fine structure of matrix vesicles in order to visualise the features of the consequent stages of their cacification in arteries. In the present work, a high resolution ultrastructural analysis has been employed and the study revealed that matrix vesicles in human atherosclerotic lesions are heterogeneous with two main types which we classified. Type I calcified vesicles were presented by vesicles surrounded by two electron-dense layers and these vesicles were dound to be resistant to the calcification process in atherosclerotic lesions in situ. Type II matrix vesicles were presnted by vesicles surrounded by several electron-dense layers and these vesicles were dound to represent calcifying vesicles in atherosclerotic lesions. To test the hypothesis that calcification of matrix vesicles surrounded by multilayer sheets may occur simply as a physiochemical process, independently from the cell regulation, we produced multilamellar liposomes and induced their calfcification in vitro in a manner similar to that ocurring in matrix vesicles in atherosclerotic lesions in situ.
Krishnamurthy, V, Luk, KY, Cornell, BA, Prashar, J, Di Maio, I, Islam, H, Battle, AR, Valenzuela, S & Martin, DK 2007, 'Gramicidin Ion Channel-Based Nano-Biosensors: Construction, Stochastic Dynamical Models and Statistical Detection Algorithms', IEEE Sensors Journal, vol. 7, no. 9, pp. 1281-1288.View/Download from: Publisher's site
This paper deals with the experimental construction, stochastic modeling, and statistical signal processing of a novel, artificially constructed biosensor comprised of biological ion channels. Such nanoscale biosensors have been built by incorporating dimeric gramicidin A (bis-gA) ion channels into bilayer membranes of giant unilamellar liposomes, and then excising small patches of the membrane loaded with ion channels. We present a stochastic model for the response of the biosensor and present statistical model validation tests to verify the adequacy of the model., We show that in the presence of specific target molecules, the statistics of the gating mechanisms of the gA channels are altered. By capturing the change in real time, we devise a maximum-likelihood detector to detect the presence of target molecules. To test the sensitivity of this model, we conducted patch-clamp experiments with two compounds known to inhibit conduction of the gA channels. We found experimentally that the real-time detection algorithm was able to accurately identify the addition of the compounds even when the alterations in the patch-clamp recordings were very small. This algorithm provides the sensitive detection system for ongoing development of lipid-based nanosensors.
Gold nanoparticles can be conjugated with antibodies or other proteins, and the resulting composite particles will selectively attach to various kinds of biological material. Although exploitation of this for staining microscopy specimens is well known, there has recently been interest in attaching gold nanoparticles to live cells for therapeutic reasons. One motication is that gold nanoparticles display a strong plasmon resonance with light, which can be exploted in principle for an 'in vivo' photothermal therapy. The treatment of cancer by this technique has recently received attention by others, but here we show how gold nanoparticle based therapies can be developed to target live macrophage cells. We have employed 'active targeting' a scheme in which gold nanoparticles are functionalised with an antibody specific to the target macrophage cell. We describe how to prepare the conjugated particles, demonstrate that they will selectively attach 'in vitro' to their target macrophage cell but not to a non-target cell type and show that their presence renders the target cell susceptible to destruction by a low power laser.
Pissuwan, D, Valenzuela, S, Killingsworth, MC, Xu, X & Cortie, MB 2007, 'Targeted destruction of murine macrophage cells with bioconjugated gold nanorods', Journal of nanoparticle Research, vol. 9, no. 6, pp. 1109-1124.View/Download from: Publisher's site
Gold nanorods manifest a readily tunable longitudinal plasmon resonance with light and consequently have potential for use in photothermal therapeutics. Recent work by others has shown how gold nanoshells and rods can be used to target cancer cells, which can then be destroyed using relatively high power laser radiation (similar to 1x10(5) to 1x10(10) W/m(2)). Here we extend this concept to demonstrate how gold nanorods can be modified to bind to target macrophage cells, and show that high intensity laser radiation is not necessary, with even 5x10(2) W/m(2) being sufficient, provided that a total fluence of similar to 30 J/cm(2) is delivered. We used the murine cell line RAW 264.7 and the monoclonal antibody CD11b, raised against murine macrophages, as our model system and a 5 mW solid state diode laser as our energy source. Exposure of the cells labeled with gold nanorods to a laser fluence of 30 J/cm(2) resulted in 81% cell death compared to only 0.9% in the control, non-labeled cells.
Pissuwan, D, Valenzuela, S, Miller, CM & Cortie, MB 2007, 'A Golden bullet? Selective targeting of Toxoplasma gondii Tachyzoites using antibody-functionalised gold nanorods', Nano Letters, vol. 7, no. 12, pp. 3808-3812.View/Download from: Publisher's site
Conjugates of gold nanoparticles and antibodies have useful functionalities. Here we show how they can be used to selectively target and destroy parasitic protozoans. Gold nanorods were conjugated with an anti-Toxoplasma gondii antibody and used to target the extracellular tachyzoite which is an infectious from on an obligate parasite Toxoplasma gondii. Subsequent laser irradiation was used to kill the targeted protozoans. This concept provides a new paradigm for the treatment of parasitic protozoans.
Pissuwan, D, Valenzuela, SM, Miller, CM & Cortie, MB 2007, 'A golden bullet? Selective targeting of toxoplasma gondii tachyzoites using antibody-functionalized gold nanorods', Nano Letters, vol. 7, no. 12, pp. 3808-3812.View/Download from: Publisher's site
Conjugates of gold nanoparticles and antibodies have useful functionalities. Here, we show how they can be used to selectively target and destroy parasitic protozoans. Gold nanorods were conjugated with an anti-Toxop/asma gondii antibody and used to target the extracellular tachyzoite which is an infectious form of an obligate parasite Toxoplasma gondii. Subsequent laser irradiation was used to kill the targeted protozoans. This concept provides a new paradigm for the treatment of parasitic protozoans. © 2007 American Chemical Society.
Gurisik, E, Warton, K, Martin, DK & Valenzuela, S 2006, 'An in vitro study of the effects of exposure to a GSM signal in two human cell lines Monocytic U937 and neuroblastoma SK-N-SH', Cell Biology International, vol. 30, no. 10, pp. 793-799.View/Download from: Publisher's site
The use of mobile phones is increasing, which also increases the population's exposure to global system of mobile communications (GSM) signals. Questions of safety and possible biological effects are of concern and to date, remain largely unanswered. In
Pissuwan, D, Valenzuela, S & Cortie, MB 2006, 'Therapeutic possibilities of plasmonically heated gold nanoparticles', Trends In Biotechnology, vol. 24, no. 2, pp. 62-67.View/Download from: Publisher's site
Nanoparticles of gold, which are in the size range 10-100 nm, undergo a plasmon resonance with light. This is a process whereby the electrons of the gold resonate in response to incoming radiation causing them to both absorb and scatter light. This effec
Zreiqat, H, Roest, RS, Valenzuela, S, Milev, AS & Ben-Nissan, B 2005, 'Human bone derived cell (HBDC) behaviour of sol-gel derived carbonate hydroxyapatite coatings on titanium alloy substrates', Bioceramics, vol. 17, no. 1, pp. 541-544.
Poor cell adhesion to orthopaedic and dental implants results in implant failure. Establishing and maintaining mature bone at the bone/device interface is critical to the long-term success of the prostheses. Considerable effort has been devoted to alter
Zreiqat, H, Valenzuela, S, Ben-Nissan, B, Roest, RS, Knabe, C, Radlanski, RJ, Renz, H & Evans, PA 2005, 'The effect of surface chemistry modification of titanium alloy on signalling pathways in human osteoblasts', Biomaterials, vol. 26, no. 36, pp. 7579-7586.View/Download from: Publisher's site
Establishing and maintaining mature bone at the bone-device interface is critical to the long-term success of prosthesis. Poor cell adhesion to orthopaedic and dental implants results in implant failure. Considerable effort has been devoted to alter the
Mazzanti, M, Warton, K, Tonini, R, Lorenzi, G, Fairlie, WD, Matthews, J, Valenzuela, S, Qiu, M, Wu, W, Pankhurst, S, Bauskin, AR, Campbell, TJ, Curmi, PM & Breit, SN 2002, 'Ncc27 (clic1) Interacts With Artifical Bylayer In A Ph Dependent Manner To Form Chloride Ion Channels', Biophysical Journal, vol. 82, no. 1, pp. 1-1.
Singarayar, S, Singleton, C, Tie, H, Wise, K, Bursill, J, Bauskin, AR, Wu, WM, Valenzuela, S, Breit, SN & Campbell, TJ 2002, 'Effects of components of ischemia on the Kv4.3 current stably expressed in Chinese hamster ovary cells', Journal of Molecular Cell Cardiology, vol. 34, no. 2, pp. 197-207.View/Download from: Publisher's site
We investigated the effects of three components of ischemia: external acidosis (pH=6.0), extracellular hyperkalemia ([K+]=20 mmol/l), and resting membrane depolarization to -60 mV, on Kv4.3 current stably expressed in Chinese Hamster Ovary cells. We used single electrode whole cell patch clamp techniques to study changes in the current elicited. External acidosis caused a positive shift in the steady state activation curve from -13.4±2.1 mV to -3.3±1.5 mV (n=8, P=0.004) and the steady state inactivation curve from -56.5±0.4 mV to -46.7±0.5 mV (n=14, P<0.0001). Acidosis also caused an acceleration of recovery from inactivation with the t1/2 decreasing from 306 ms (95% CI 287327 ms) to 194 ms (95% CI 182207 ms), (n=14, P<0.05). Hyperkalemia did not affect any of these parameters. Combined acidosis and hyperkalemia produced effects similar to those seen with acidosis. Changing the holding potential from -90 mV to -60 mV with test potentials of +5 and +85 mV decreased the peak currents by 34.1% and 32.4% respectively (n=14). However, in the presence of external acidosis the decrease in peak currents induced by changing the holding potential was less marked. In acidotic bath the peak current at -60 mV was reduced by only 13.6% at a test potential of +5 mV and 12.3% at a test potential of +85 mV (n=14). Taken together our data suggest that the membrane depolarization and changes in pH which occur under ischemic conditions would be accompanied by relative preservation of Kv4.3 currents and provide a molecular basis for the observation of preserved epicardial Ito and epicardial action potential duration (APD) shortening in ischemia.
Warton, K, Tonini, R, Fairlie, WD, Matthews, JM, Valenzuela, S, Qui, MR, Wu, WM, Pankhurst, S, Bauskin, AR, Harrop, SJ, Campbell, TJ, Curmi, PM, Breit, SN & Mazzanti, M 2002, 'Recombinant CLIC1 (NCC27) assembles in lipid bilayers via a pH-dependent two-state process to form chloride ion channels with identical characteristics to those observed in CHO cells expressing CLIC1', Journal Of Biological Chemistry, vol. 277, no. 29, pp. 26003-26011.View/Download from: Publisher's site
CLIC1 (NCC27) is an unusual, largely intracellular, ion channel that exists in both soluble and membrane-associated forms. The soluble recombinant protein can be expressed in Escherichia coli, a property that has made possible both detailed electrophysiological studies in lipid bilayers and an examination of the mechanism of membrane integration. Soluble E. coli-derived CLIC1 moves from solution into artificial bilayers and forms chloride-selective ion channels with essentially identical conductance, pharmacology, and opening and closing kinetics to those observed in CLIC1-transfected Chinese hamster ovary cells. The process of membrane integration of CLIC1 is pH-dependent. Following addition of protein to the trans solution, small conductance channels with slow kinetics (SCSK) appear in the bilayer. These SCSK modules then appear to undergo a transition to form a high conductance channel with fast kinetics. This has four times the conductance of the SCSK and fast kinetics that characterize the native channel. This suggests that the CLIC1 ion channel is likely to consist of a tetrameric assembly of subunits and indicates that despite its size and unusual properties, it is able to form a completely functional ion channel in the absence of any other ancillary proteins.
Harrop, SJ, DeMaere, MZ, Fairlie, WD, Reztsova, T, Valenzuela, S, Mazzanti, M, Tonini, R, Qui, MR, Jankova, L, Warton, K, Bauskin, AR, Wu, WM, Pankhurst, S, Campbell, TJ, Breit, SN & Curmi, PM 2001, 'Crystal structure of the soluble form of the intracellular chloride channel CLIC1 (NCC27) at 1.4-angstrom Resolution', Journal Of Biological Chemistry, vol. 276, no. 48, pp. 44993-45000.View/Download from: Publisher's site
CLIC1 (NCC27) is a member of the highly conserved class of chloride ion channels that exists in both soluble and integral membrane forms. Purified CLIC1 can integrate into synthetic lipid bilayers forming a chloride channel with similar properties to those observed in vivo. The structure of the soluble form of CLIC1 has been determined at 1.4-Angstrom resolution. The protein is monomeric and structurally homologous to the glutathione S-transferase superfamily, and it has a redox-active site resembling glutaredoxin. The structure of the complex of CLIC1 with glutathione shows that glutathione occupies the redox-active site, which is adjacent to an open, elongated slot lined by basic residues. Integration of CLIC1 into the membrane is likely to require a major structural rearrangement, probably of the N-domain (residues 1-90), with the putative transmembrane helix arising from residues in the vicinity of the redox-active site. The structure indicates that CLIC1 is likely to be controlled by redox-dependent processes.
Mazzanti, M, Valenzuela, S, Tonini, R, Qui, MR, Warton, K, Musgrove, E, Campbell, TJ & Fairle, D 2001, 'The Nuclear Chloride Ion Channel Ncc27 Is Involved In Regulation Of The Cell Cycle', Biophysical Journal, vol. 80, no. 1, pp. 1-1.
Raftery, MJ, Yang, Z, Valenzuela, S & Geczy, CL 2001, 'Novel intra-and inter-molecular sulfinamide bonds in S100A8 produced by hypochlorite oxidation', Journal Of Biological Chemistry, vol. 276, no. 36, pp. 33393-33401.View/Download from: Publisher's site
Hypochlorite is a major oxidant generated when neutrophils and macrophages are activated at inflammatory sites, such as in atherosclerotic lesions. Murine S100A8 (A8) is a major cytoplasmic protein in neutrophils and is secreted by macrophages in response to inflammatory stimuli. After incubation with reagent HOCl for 10 min, ~85% of A8 was converted to 4 oxidation products, with electrospay ionization mass spectrometry masses of m/z 10354, 10388, 10354 ± 1, and 20707 ± 3. All were resistant to reduction by dithiothreitol. Initial formation of a reactive Cys sulfenic acid intermediate was demonstrated by the rapid conjugation of 5,5-dimethyl-1,3-cyclohexanedione (dimedone) to HOCl-treated A8 to form stable adducts. Matrix-assisted laser desorption-reflectron time of flight peptide mass fingerprinting of isolated oxidation products confirmed the mass additions observed in the full-length proteins. Both Met36/73 were converted to Met36/73 sulfoxides. An additional product with an unusual mass addition of m/z 14 (±0.2) was identified and corresponded to the addition of oxygen to Cys41, conjugation to various epsilon -amines of Lys6, Lys34/35, or Lys87 with loss of dihydrogen and formation of stable intra- or inter-molecular sulfinamide cross-links. Specific fragmentations identified in matrix-assisted laser desorption-post source decay spectra and low energy collisional-induced dissociation tandem mass spectroscopy spectra of sulfinamide-containing digest peptides confirmed Lys34/35 to Cys41 sulfinamide bonds. HOCl oxidation of mutants lacking Cys41 (Ala41S100A8) or specific Lys residues (e.g. Lys34/35, Ala34/35S100A8) did not form sulfinamide cross-links. HOCl generated by myeloperoxidase and H2O2 and by phorbol 12-myristate 13-acetate-activated neutrophils also formed these products.
Tie, H, Walker, BD, Singleton, C, Bursill, J, Wyse, KR, Valenzuela, S, Breit, SN & Campbell, TJ 2001, 'Clozapine and sudden death', Journal of Clinical Psychopharmacology, vol. 21, no. 6, pp. 630-632.
Walker, BD, Tie, H, Singleton, C, Bursill, J, Wyse, KR, Bauskin, AR, Valenzuela, S, Wu, W, Breit, SN & Campbell, TJ 2001, 'Modification Of Herg Channel Properties Under Conditions Of Simulated Myocardial Ischemia', Journal Of The American College Of Cardiology, vol. 37, no. 2, pp. 1-2.
Idle, JR, Tie, F, Walker, BD, Valenzuela, SM, Breit, SN & Campbell, TJ 2000, 'The heart of psychotropic drug therapy (multiple letters)', Lancet, vol. 355, no. 9217, pp. 1824-1825.View/Download from: Publisher's site
Tie, H, Walker, BD, Singleton, C, Bursill, J, Wyse, KR, Valenzuela, S, Qiu, M, Breit, SN & Campbell, TJ 2000, 'The Antipsychotic Agents Thioridazine, Chlorpromazine And Clozapine Block The Human-ether-a-go-go-related Gene (herg) Potassium Channel: Cellular Mechanism For Proarrhythmia', Journal Of The American College Of Cardiology, vol. 35, no. 2, pp. 1-1.
Tie, H, Walker, BD, Singleton, CB, Valenzuela, S, Bursill, JA, Wyse, KR, Breit, SN & Campbell, TJ 2000, 'Inhibition of HERG potassium channels by the antimalarial agent halofantrine', British Journal of Pharmacology, vol. 130, no. 8, pp. 1967-1975.View/Download from: Publisher's site
Halofantrine is a widely used antimalarial agent which has been associated with prolongation of the 'QT interval' of the electrocardiogram (ECG), torsades de pointes and sudden death. Whilst QT prolongation is consistent with halofantrine-induced increases in cardiac ventricular action potential duration, the cellular mechanism for these observations has not been previously reported. 2. The delayed rectifier potassium channel, I(Kr), is a primary site of action of drugs causing QT prolongation and is encoded by the human-ether-a-go-go-related gene (HERG). We examined the effects of halofantrine on HERG potassium channels stably expressed in Chinese hamster ovary (CHO-K1) cells. 3. Halofantrine blocked HERG tail currents elicited on repolarization to -60 mV from + 30 mV with an IC 50 of 196.9 nM. The therapeutic plasma concentration range for halofantrine is 1.67-2.98 uM. 4. Channel inhibition by halofantrine exhibited time-, voltage- and use-dependence. Halofantrine did not alter the time course of channel activation or deactivation, but inactivation was accelerated and there was a 20 mV hyperpolarizing shift in the mid-activation potential of steady-state inactivation. Block was enhanced by pulses that render channels inactivated, and channel blockade increased with increasing duration of depolarizing pulses. 5. We conclude that HERG channel inhibition by halofantrine is the likely underlying cellular mechanism for QT prolongation. Our data suggest preferential binding of halofantrine to the open and inactivated channel states.
Tie, H, Walker, BD, Valenzuela, S, Breit, SN & Campbell, TJ 2000, 'The Heart Of Psychotropic Drug Therapy', Lancet, vol. 355, no. 9217, pp. 1825-1825.
Tie, H, Walker, BD, Valenzuela, S, Breit, SN & Campbell, TJ 2000, 'The heart of psychotropic drug therapy.', The Lancet, vol. 355, no. May 20, pp. 1824-1825.
In two consecutive issues, The Lancet has published articles that clearly link CYP2D6 (debrisoquine hydroxylase) and the human heart. First, Thomas Thum and Jürgen Borlak (March 18, p 979)1 reported the expression of several cytochrome P450 (CYP) genes, including CYP2D6, in the right ventricle, and J G Reilly and colleagues (March 25, p 1048)2 noted certain risk factors in psychiatric patients undergoing psychotropic drug therapy.
Tonini, R, Ferroni, A, Valenzuela, S, Warton, K, Campbell, TJ, Breit, SN & Mazzanti, M 2000, 'Functional characterization of the NCC27 nuclear protein in stable transfected CHO-K1 cells', Faseb Journal, vol. 14, no. 9, pp. 1171-1178.
NCC27 belongs to a family of small, highly conserved, organellar ion channel proteins. It is constitutively expressed by native CHO-K1 and dominantly localized to the nucleus and nuclear membrane. When CHO-K1 cells are transfected with NCC27-expressing c
Valenzuela, S, Mazzanti, M, Tonini, R, Qiu, M, Warton, K, Musgrove, E, Campbell, TJ & Breit, SN 2000, 'The Nuclear Chloride Ion Channel NCC27 Is Involved In Regulation Of The Cell Cycle', Journal Of Physiology-london, vol. 529, no. 3, pp. 541-552.View/Download from: Publisher's site
1. NCC27 is a nuclear chloride ion channel, identified in the PMA-activated U937 human monocyte cell line. NCC27 mRNA is expressed in virtually all cells and tissues and the gene encoding NCC27 is also highly conserved. Because of these factors, we have
Walker, BD, Singleton, C, Tie, H, Bursill, J, Wyse, KR, Valenzuela, S, Breit, SN & Campbell, TJ 2000, 'Comparative Effects Of Azimilide And Ambasilide On The Human Ether-a-go-go-related Gene (herg) Potassium Channel', Cardiovascular Research, vol. 48, no. 1, pp. 44-58.View/Download from: Publisher's site
Objective: To evaluate the effects of azimilide and ambasilide on the biophysical properties of the human-ether-a-go-go-related (HERC) channel. Methods: HERG was stably transfected into Chinese hamster ovary (CHO-K1) cells and currents were measured using a whole cell, voltage-clamp technique. Results: Azimilide had a 'dual effect', inhibiting current at voltage steps above -40 mV and augmenting current at -40 and -50 mV. Tail current inhibition following a step to +30 mV did not vary with temperature (IC50 610 nM at 22 degrees C and 560 nM at 37 degrees C). The agonist effect at -50 mV was concentration-dependent and correlated with a hyperpolarizing shift in the V-1/2 of activation (r = 0.98, P < 0.05). Time constants of inactivation were faster and there was a -10 mV shift in the V-1/2 of steady state inactivation suggestive of open and inactivated state binding. By comparison, ambasilide inhibited HERG channels with lower potency (IC50 3.6 mu M), in a voltage- and time-dependent but frequency-independent manner (0.03-1 Hz). Ambasilide had no effect on activation or inactivation gating but prolonged both fast and slow components of deactivation consistent with unbinding from the open state. The net effect of both drugs was similar during a voltage ramp which simulated a cardiac action potential. Conclusions: Inhibition of HERG channels by azimilide and ambasilide exhibits a similar time and voltage-dependence. While both exhibit affinity for the open state, azimilide also binds to inactivated channels.
Singleton, C, Valenzuela, S, Walker, BD, Tie, H, Wyse, KR, Bursill, J, Qiu, M, Breit, SN & Campbell, TJ 1999, 'Blockade By N-3 Polyunsaturated Fatty Acid Of The Kv4.3 Current Stably Expressed In Chinese Hamster Ovary Cells', British Journal Of Pharmacology, vol. 127, no. 4, pp. 941-948.View/Download from: Publisher's site
The Kv4.3 gene is believed to encode a large proportion of the transient outward current (I-to), responsible for the early phase of repolarization of the human cardiac action potential. There is evidence that this current is involved in the dispersion of refractoriness which develops during myocardial ischaemia and which predisposes to the development of potentially fatal ventricular tachyarrhythmias. Epidemiological, clinical, animal, and cellular studies indicate that these arrhythmias may be ameliorated in myocardial ischaemia by n-3 polyunsaturated fatty acids (n-3 PUFA) present in fish oils. We describe stable transfection of the Kv4.3 gene into a mammalian cell line (Chinese hamster ovary cells), and using patch clamp techniques have shown that the resulting current closely resembles human I-to. The current is rapidly activating and inactivating, with both processes being well fit by double exponential functions (time constants of 3.8 +/- 0.2 and 5.3 +/- 0.4 ms for activation and 20.0 +/- 1.2 and 96.6 +/- 6.7 ms for inactivation at +45 mV at 23 degrees C). Activation and steady state inactivation both show voltage dependence (V-1/2 Of activation = -6.7 +/- 2.5 mV, V-1/2 Of steady state inactivation = -51.3 +/- 0.2 mV at 23 degrees C). Current inactivation and recovery from inactivation are faster at physiologic temperature (37 degrees C) compared to room temperature (23 degrees C). The n-3 PUFA docosahexaenoic acid blocks the Kv4.3 current with an IC50 of 3.6 mu mol L-1. Blockade of the transient outward current may be an important mechanism by which n-3 PUFA provide protection against the development of ventricular fibrillation during myocardial ischaemia.
Singleton, C, Walker, BD, Bursill, J, Wyse, KR, Valenzuela, S, Breit, SN & Campbell, TJ 1999, 'Potential Cellular Mechanism For The Antifibrillatory Properties Of Fish Oils: Potent Blockade Of Kv4.3 Current (i-to)', Circulation, vol. 100, no. 18, pp. 279-279.
Walker, BD, Singleton, C, Bursill, J, Wyse, KR, Valenzuela, S, Qiu, M, Breit, SN & Campbell, TJ 1999, 'Inhibition Of The Human Ether-a-go-go-related Gene (HERG) potassium Channel By Cisapride: Affinity For Open And Inactivated States', British Journal Of Pharmacology, vol. 128, no. 2, pp. 444-450.View/Download from: Publisher's site
Cisapride is a prokinetic agent which has been associated with QT prolongation, torsades de pointes and cardiac arrest. The cellular mechanism for these observations is high affinity blockade of I-Kr (encoded by HERG). In a chronic transfection model using CHO-K1 cells, cisapride inhibited HERG tail currents after a step to + 25 mV with similar potency at room and physiological temperatures (IC50 16.4 nM at 20-22 degrees C and 23.6 nM at 37 degrees C). Channel inhibition exhibited time-, voltage- and frequency-dependence. In an envelope of tails test, channel blockade increased from 27+/-8% after a 120 ms depolarizing step to 50+/-4% after a 1.0 s step. These findings suggested affinity for open and/or inactivated channel states. Inactivation was significantly accelerated by cisapride in a concentration-dependent manner and there was a small (-7 mV) shift in the voltage dependence of steady state inactivation. Channel blockade by cisapride was modulated by [K+](o), with a 26% reduction in the potency of channel blockade when [K+](o) was increased from 1 to 10 mM. In conclusion, HERG channel inhibition by cisapride exhibits features consistent with open and inactivated state binding and is sensitive to external potassium concentration. These features may have significant clinical implications with regard to the mechanism and treatment of cisapride-induced proarrhythmia.
Walker, BD, Valenzuela, S, Singleton, C, Tie, H, Bursill, J, Wyse, KR, Qiu, M, Breit, SN & Campbell, TJ 1999, 'Inhibition Of Herg Channels Stably Expressed In A Mammalian Cell Line By The Antianginal Agent Perhexiline Maleate', British Journal Of Pharmacology, vol. 127, no. 1, pp. 243-251.View/Download from: Publisher's site
Perhexiline has been used as an anti-anginal agent for over 25 years, and is known to cause QT prolongation and torsades df pointes. We hypothesized that the cellular basis for these effects was blockade of I-Kr. A stable transfection of HERG into a CHO-KI cell line produced a delayed rectifier, potassium channel with similar properties to those reported for transient expression in Xenopus oocytes. Perhexiline caused voltage- and frequency-dependent block of HERG (IC50 7.8 mu M). The rate of inactivation was increased and there was a 10 mV hyperpolarizing shift in the voltage-dependence of steady-state inactivation, suggestive of binding to the inactivated state. In conclusion, perhexiline potently inhibits transfected HERG channels and this is the probable mechanism for QT prolongation and torsades de pointes. Channel blockade shows greatest affinity for the inactivated state.
Mazzanti, M, Tonini, R, Valenzuela, S & Breit, SN 1998, 'Molecular Cloning And Functional Expression Of A Novel Nuclear Chloride Ion Channel', Pflugers Archiv-european Journal Of Physiology, vol. 436, no. 5, pp. 1-1.
Bootcov, M, Bauskin, AR, Valenzuela, S, Moore, A, Bansal, M, He, X, Zhang, H, Donnellan, M, Mahler, S, Pryor, K, Walsh, B, Nicholson, RC, Fairlie, WD, Por, S, Robbins, J & Breit, SN 1997, 'MIC-1, A Novel Macrophage Inhibitory Cytokine, Is A Divergent Member Of The TGF-beta Superfamily', Proceedings Of The National Academy Of Sciences Of The United States Of America, vol. 94, no. 21, pp. 11514-11519.View/Download from: Publisher's site
Macrophages play a key role in both normal and pathological processes involving immune and inflammatory responses, to a large extent through their capacity to secrete a wide range of biologically active molecules, To identify some of these as yet not characterized molecules, we have used a subtraction cloning approach designed to identify genes expressed in association with macrophage activation, One of these genes, designated macrophage inhibitory cytokine 1 (MIC-1), encodes a protein that bears the structural characteristics of a transforming growth factor beta (TGF-beta) superfamily cytokine, Although it belongs to this superfamily it has no strong homology to existing families, indicating that it is a divergent member that may represent the first of a new family within this grouping, Expression of MIC-1 mRNA in monocytoid cells is up-regulated by a variety of stimuli associated with activation, including interleukin 1 beta, tumor necrosis factor alpha (TNF-alpha), interleukin 2, and macrophage colony-stimulating factor but not interferon gamma, or lipopolysaccharide (LPS), Its expression is also increased by TGF-beta, Expression of MIC-1 in CHO cells results in the proteolytic cleavage of the propeptide and secretion of a cysteine-rich dimeric protein of M-r 25 kDa, Purified recombinant MIC-1 is able to inhibit lipopolysaccharide -induced macrophage TNF-alpha production, suggesting that MIC-1 acts in macrophages as an autocrine regulatory molecule, Its production in response to secreted proinflammatory cytokines and TGF-beta may serve to limit the later phases of macrophage activation.
Valenzuela, S, Martin, DK, Por, S, Robbins, J, Warton, K, Bootcov, M, Schofield, P, Campbell, TJ & Breit, SN 1997, 'Molecular Cloning And Expression Of A Chloride Ion Channel Of Cell Nuclei', Journal Of Biological Chemistry, vol. 272, no. 19, pp. 12575-12582.View/Download from: Publisher's site
Ion channels are known to be present on the plasma membrane of virtually all cells and have been found on the membranes of various intracellular organelles. However, until recently they were believed not to occur at the nuclear membrane. In this study we describe the molecular cloning and characterization of a nuclear ion channel protein, designated nuclear chloride channel-27 (NCC27), from the human myelomonocytic cell line, U937. NCC27 is a novel chloride ion channel protein that was found to localize principally to the cell nucleus, Its only known homologue is a bovine chloride ion channel protein (p64) believed to localize to internal organelles. NCC27 therefore represents the first human member of a new class of organellar chloride ion channel proteins.
Shimoni, O & Valenzuela, S 2018, 'Gold Nanoparticles with Organic Linkers for Applications in Biomedicine' in Vo-Dinh, T (ed), Nanotechnology in Biology and Medicine: Methods, Devices, and Applications, CRC Press - Taylor & Francis Group, USA, pp. 84-99.
Valenzuela, S 2007, 'Liposome techniques for synthesis of biomimetic lipid membranes' in Ferrari, M & Martin, D (eds), Nanobiotechnology of biomimetic membranes, Springer, New York, USA, pp. 75-87.View/Download from: Publisher's site
The lipid bilayer is the universal basis for cell membrane structure. Historically, the formation of this bilayer into a closed, spherical vesicle, essentially a microscopic sac, resulted in the creation of a boundary separating the internal environment (lumen) from the external environment. This very basic vesicle structure with its semipermeable properties, has formed the basis for the development of life on earth as we know it.The term used to describe these closed spherical structures is a liposome. These bilayer vesicles form spontaneously when phospholipids (containing 2 hydrocarbon chains and a hydrophilic polar head group) are exposed to an aqueous environment. This was first demonstrated in 1965 by Bangham and his colleagues! who were studying the diffusion of univalent ions across what they described as "spontaneonsly formed liquid crystals of lecithin". They reported that ions diffused across these artificial membranes in a manner highly analogous to that observed in biological membranes.
Hossain, KR, Al Khamici, H, Holt, SA & Valenzuela, SM 2016, 'Elucidating the Mechanism for Sterol Regulation of Chloride Intracellular Ion Channel Protein Interactions with Lipid Membranes', BIOPHYSICAL JOURNAL, 60th Annual Meeting of the Biophysical-Society, CELL PRESS, Los Angeles, CA, pp. 204A-204A.View/Download from: Publisher's site
Cornell, BA, Alkhamici, H, Brown, L, Carne, S, Goodchild, SC, Richards, R & Valenzuela, SM 2012, 'Ion Channel Proteins that Spontaneously Insert into Lipid Bilayer Membranes: An Impedance Spectroscopy Study Employing Tethered Membranes', BIOPHYSICAL JOURNAL, 56th Annual Meeting of the Biophysical-Society, CELL PRESS, San Diego, CA, pp. 682A-683A.View/Download from: Publisher's site
Gunning, SJ, Maggio, FJ, Windley, MJ, Valenzuela, S, King, GF & Nicholson, GM 2009, 'Janus-faced atracotoxins are specific blockers of invertebrate KCa channels', 34th Congress of the Federation of European Biochemical Societies, Prague, Czech Republic.
Lewis, KC, Wuhrer, R, Ben-Nissan, B, Valenzuela, S & Moran, K 2009, 'X-ray mapping of minerals incorporated into liposomes', Microscopy and Microanalysis 2009, Microscopy and Microanalysis 2009, Cambridge University Press, Richmond, Virginia, USA, pp. 908-909.View/Download from: Publisher's site
Liposomes are spherical particles in an aqueous medium formed by a lipid bilayer enclosing an aqueous compartment. They have been long considered as a potential delivery device in the medical and pharmaceutical industries due to their ability to encapsulate different compounds, as the lipids form into liposomes. The ability of these liposomes to be stored in the body, and to be taken up by cells, makes them ideal for drug delivery. They can also potentially increase the efficiency of supplements, particularly those with no accumulation toxicity.
Nicholson, GM, Gunning, SJ, Windley, MJ, Maggio, FJ, Valenzuela, S & King, GF 2009, 'Defining the lethal ion channel targets of insecticidal spider toxins', 16th World Congress on Animal, Plant and Microbial Toxins.
Lewis, K, Valenzuela, SM & Ben-Nissan, B 2008, 'Sol-gel derived hydroxyapatite and zirconia nanocoatings, and the effect on the activity of osteoblast like cells', 8th World Biomaterials Congress 2008, p. 567.
Nicholson, GM, Gunning, SJ, Maggio, FJ, Windley, MJ, Valenzuela, S & King, GF 2009, 'Identifying novel insecticide targets using insect-specific spider toxins', 3rd International Congress on Natural Peptides to Drugs, Zermatt, Switzerland.
Windley, MJ, Escoubas, P, Valenzuela, S & Nicholson, GM 2008, 'Characterisation of a family of insect-selective neurotoxins isolated from the African tarantula, Eucratoscelus longiceps', 8th Asia-Pacific Congress on Animal, Plant & Microbial Toxins, Hanoi and Halong Bay, Vietnam.
Di Maio, I, Carl, D, Langebanenberg, P, Valenzuela, S, Battle, AR, Al Khazaaly, S, Killingsworth, M, Kemper, B, von Bally, G & Martin, DK 2005, 'Structural properties of liposomes from digital holographic microscopy - art. no. 60361R', Biomems And Nanotechnology Ii, Conference on BioMEMS and Nanotechnology II, Spie-Int Society Optical Engineering, Brisbane, AUSTRALIA, pp. 1-9.
We have constructed liposomes from L-alpha-Phosphatidylcholine (PC) lipids, which are biomimetic lipids similar to those present in the membranes of mammalian cells. We propose an advance in the use of liposomes, such as for drug delivery, to incorporate into the liposomal membranes transport proteins that have been extracted from the lipid membranes of mammalian cells. In this paper, we describe the usage of a novel optical microscope to characterize the nanomechanical properties of these liposomes. We have applied the technique of digital holographic microscopy(1), using an instrument recently developed at the University of Munster, Germany. This system enabled us to measure quantitatively the structural changes in liposomes. We have investigated the deformations of these biomimetic lipids comprising these liposomes by applying osmotic stresses, in order to gain insight into the membrane environment prior to incorporation of cloned membrane transport proteins. This control of the nanomechanical properties is important in the stresses transmitted to mechanosensitive ion channels that we have incorporated into the liposomal membranes. These liposomes provide transporting vesicles that respond to mechanical stresses, such as those that occur during implantation.
Gunning, SJ, Maggio, FJ, Valenzuela, S, Broady, KW, King, GK & Nicholson, GM 2006, 'Pharmacophore mapping of the Îº-atracotoxins: selective insect potassium channel blockers that reveal a novel insecticide target', 15th World Congress on Animal, Plant and Microbial Toxins, Glasgow, Scotland.
Mortari, A, Brown, NL, Geczy, CL, Coster, H, Valenzuela, S, Martin, DK & Csoregi, E 2006, 'Applications of Protein-Based Capacitive Biosensors', IEEE ICONN 2006, IEEE International Conference on Nanoscience and Nanotechnology, IEEE, Brisbane, Australia, pp. 235-238.View/Download from: Publisher's site
Three different methods of using protein-based capacitive biosensors for the detection of heavy-metal ions are presented. The metal-binding proteins SmtA, S100A12, MerP and four modified MerPs were immobilised as the biorecognition element on self-assembled monolayer-modified gold electrodes. Capacitance was measured using potential square step or electrical impedance spectroscopy. The protein-metal interaction generated changes in capacitance mainly due to a protein conformational change.
Mortari, A, Browns, NL, Geczy, C, Coster, HGL, Valenzuela, SM, Martin, D & Csoregi, E 2006, 'Applications of protein-based capacitive Biosensors for the detection of heavy-metal ions', 2006 INTERNATIONAL CONFERENCE ON NANOSCIENCE AND NANOTECHNOLOGY, VOLS 1 AND 2, International Conference on Nanoscience and Nanotechnology, IEEE, Brisbane, AUSTRALIA, pp. 304-+.
Valenzuela, S, Berkahn, MB, Martin, DK, Huynh, T, Yang, Z & Geczy, CL 2005, 'Elucidating the structure and function of S100 proteins in membranes - art. no. 603619', Biomems And Nanotechnology Ii, Conference on BioMEMS and Nanotechnology II, Spie-Int Society Optical Engineering, Brisbane, AUSTRALIA, pp. 3619-3619.
100 proteins are important Ca2+-binding proteins involved in vital cellular functions including the modulation of cell growth, migration and differentiation, regulation of intracellular signal transduction/phosphorylation pathways, energy metabolism, cyt
Gunning, SJ, Maggio, FJ, Valenzuela, S, Broady, KW, King, GK & Nicholson, GM 2005, 'Îº-Atracotoxins: Insect potassium channels blockers that reveal a novel insecticide target', Venoms to Drugs 3, Heron Island, QLD.
Gunning, SJ, Maggio, FJ, Valenzuela, S, Broady, KW, King, GK & Nicholson, GM 2005, 'Selective actions of Îº-atracotoxins on insect KCa channels: electrophysiological validation of the insect target and pharmacophore', 7th Asia Pacific Congress on Animal, Plant and Microbial Toxins, Cebu City, Philippines.
Valenzuela, S, Martin, DK, Por, S, Robbins, J, Bootcov, M, Schofield, P, Campbell, TJ & Breit, SN 1996, 'NCC27 - A Novel Nuclear Chloride Ion Channel Associated With Macrophage Activation.', Journal Of Leukocyte Biology, Federation Amer Soc Exp Biol, ISI:A1996VE90600106, pp. 106-106.
Breit, SN, Robbins, J, Sutherland, G, Por, S & Valenzuela, S 1994, 'The Cloning And Characterization Of A Novel Macrophage Activation Gene', Faseb Journal, Federation Amer Soc Exp Biol, ISI:A1994ND19601234, pp. 1-1.
Bootcov, M, Por, S, Robbins, J, Valenzuela, S & Breit, SN 1993, 'The Isolation And Characterization Of A Macrophage Activation Gene', Journal Of Leukocyte Biology, Federation Amer Soc Exp Biol, ISI:A1993ME18500478, pp. 113-113.
Valenzuela, S, Por, S, Robbins, J & Breit, SN 1993, 'Subtraction Cloning Of A Novel Activation Gene In U937 Cells', Journal Of Leukocyte Biology, Federation Amer Soc Exp Biol, ISI:A1993ME18500495, pp. 116-116.
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