ANSTO :: Browsing by Author "Knott, RB"

Browsing by Author "Knott, RB"

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An16-resilin: An advanced multi-stimuli-responsive resilin-mimetic protein polymer
(Elsevier, 2014-11-01) Rajkamal, B; Dutta, NK; Choudhury, NR; Elvin, CM; Lyon, RE; Knott, RB; Hill, AJ
Engineered protein polymers that display responsiveness to multiple stimuli are emerging as a promising class of soft material with unprecedented functionality. The remarkable advancement in genetic engineering and biosynthesis has created the opportunity for precise control over the amino acid sequence, size, structure and resulting functions of such biomimetic proteins. Herein, we describe the multi-stimuli-responsive characteristics of a resilin-mimetic protein, An16-resilin (An16), derived from the consensus sequence of resilin gene in the mosquito Anopheles gambiae. We demonstrate that An16 is an intrinsically disordered protein that displays unusual dual-phase thermal transition behavior along with responsiveness to pH, ion, light and humidity. Identifying the molecular mechanisms that allow An16 to sense and switch in response to varying environments furthers the ability to design intelligent biomacromolecules. © 2014 Acta Materialia Inc.
Behaviour of single transmembrane peptides during in meso crystallization from the contrast-matched lipidic cubic phase of monoolein
(Australian Institute of Nuclear Science and Engineering (AINSE), 2018-11-19) van't Hag, L; de Campo, L; Tran, N; Sokolova, AV; Trenker, R; Call, M; Garvey, CJ; Leung., A; Darwish, TA; Krause-Heuer, AM; Knott, RB; Meikle, T; Gras, S; Drummond, CJ; Mezzenga, R; Conn, C
In meso membrane protein crystallization within a lipidic mesophase has revolutionized the structural biology of integral membrane proteins (IMPs). High-resolution structures of these proteins are crucial to understanding fundamental cellular processes at a molecular level, and can lead to new and improved treatments for a wide range of diseases via rational drug design. However, overall success rates of the promising in meso crystallization technique remain low because of a fundamental lack of understanding about factors that promote crystal growth. In particular, to date, two decades from invention of the method, the protein-eye-view of the in meso crystallization mechanism had not been solved. We have investigated this for the first time using small-angle neutron scattering (SANS). Contrast-matching between the scattering of the lipid membrane formed by MO and the aqueous solution was used to isolate and track the scattering of single-transmembrane peptides during the growth of protein crystals in meso. No peptide enrichment was observed at the flat points of the diamond cubic QIID phase of MO in contrast to suggestions in several modeling studies. During in meso crystallization of the DAP12 peptide a decrease in form factor and a transient fluid lamellar Lα phase could be observed providing direct evidence for the proposed crystallization mechanism. Synthesis of fully deuterated MO was required for this purpose and scattering of this new material in various solvents and under a range of conditions will be described, specifically regarding the effect of the relative scattering length densities (SLD) of the headgroup, acyl chain and solvent, which can advance the use of neutron scattering with other self-assembly materials. © The Authors.
Composite polymer electrolyte containing ionic liquid and functionalized polyhedral oligomeric silsesquioxanes for anhydrous PEM applications
(American Chemical Society, 2009-06-24) Subianto, S; Mistry, MK; Choudhury, NR; Dutta, NK; Knott, RB
A new type of supported liquid membrane was made by combining an ionic liquid (IL) with a Nafion membrane reinforced with multifunctional polyhedral oligomeric silsesquioxanes (POSSs) using a layer-by-layer strategy for anhydrous proton-exchange membrane (PEM) application. The POSS was functionalized by direct sulfonation, and the sulfonated POSS (S-POSS) was incorporated into Nafion 117 membranes by the infiltration method. The resultant hybrid membrane shows strong ionic interaction between the Nafion matrix and the multifunctional POSS, resulting in increased glass transition temperature and thermal stability at very low loadings of S-POSS (1%). The presence of S-POSS has also improved the proton conductivity especially at low humidities, where it shows a marked increase due to its confinement in the ionic domains and promotes water uptake by capillary condensation. In order to achieve anhydrous conductivity, the IL 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMI-BTSI) was incorporated into these membranes to provide proton conduction in the absence of water. Although the incorporation of an IL shows a plasticizing effect on the Nafion membrane, the S-POSS composite membrane with an IL shows a higher modulus at high temperatures compared to Nafion 117 and a Nafion−IL membrane, with significantly higher proton conductivity (5 mS/cm at 150°C with 20% IL). This shows the ability of the multifunctional POSS and IL to work symbiotically to achieve the desirable proton conductivity and mechanical properties of such membranes by enhancing the ionic interaction within the material. © 2009, American Chemical Society
Depressurization of an expanded solution into aqueous media for the bulk production of liposomes
(American Chemical Society, 2009-01-06) Meure, LA; Knott, RB; Foster, NR; Dehghani, F
A new dense gas process for the formation of liposomes has been developed: depressurization of an expanded solution into aqueous media (DESAM). The technique provides a fast and simple process for bulk liposome formation. As an alternative to current dense gas technologies, the DESAM process reduces the pressure requirements for liposome formation. Liposomes with diameters between 50 and 200 nm were formed. For all samples produced using ethanol as the solvent, the average effective diameter ranged from 119 to 207 nm. When chloroform was used as the solvent, the average effective diameter increased to 387 nm. The residual solvent volume fraction in the liposomal product was less than 4% v/v, which is approximately one-quarter of the value reported for some other dense gas liposome formation methods. The liposomal samples were stored after formation at 5 degrees C for up to 8 months, with the average effective diameter and polydispersity increasing by only 13% and 7%, respectively, indicating high stability of the formulations. © 2009, American Chemical Society
Deuterium effects in human serum albumin with nanoparticle silica kinetics
(Australian Institute of Nuclear Science and Engineering, 2016-11-29) White, JW; Raynes, JK; Mata, JP; Gilbert, EP; Knott, RB; de Campo, L
Light scattering shows three stages of the interaction of 80Å radius silica nanoparticles with human serum albumin in buffered solutions. The structures formed in the fast stage, twenty minutes after mixing, have been identified in a “stopped flow” neutron small angle scattering experiment. Good scattering functions were obtained at two-minute time resolution for this phase of the interaction in D2O and H2O. pH dependent changes in structure are analysed using standard fitting programs with a minimum number of parameters. This experiment was aimed to find the structural signature of nanoparticle-protein interaction, possibly the “protein corona” supposed to be formed as a means to promote entry of nanoparticles into cells. Here we use small “engineered” nanoparticles where the indications of toxicity are strong. We show with nanometric resolution that for our system, the association is largely a form of protein-induced aggregation distinct from the protein corona hypothesis. The corona might well be the mode of interaction for small proteins and nanoparticles 10-100 times larger than we have studied, but measurements on widely used commercial products may be more relevant.
Development of PET and SPECT radiopharmaceuticals to study multi-drug resistance (MDR)
(Australian Nuclear Science and Technology Organisation, 2002-04-29) Katsifis, A; Guilloteau, D; Dikic, B; Garrigos, M; Emond, P; Greguric, I; Knott, RB; Marvel, S; Mattner, F
Cellular resistance or Multidrug Resistance (MDR) to cytotoxic agents is the major cause of treatment failure in many human cancers. P-glycoprotein (Pgp), a Mr 17,0000 transmembrane protein and Multi Resistance Protein (MRP) are two proteins that are over expressed and confer resistance to a large number of chemotherapeutic agents by enhancing their extracellular transport. P-glycoprotein is expressed at a relative high level in treated and untreated human malignant tumours, including renal, colonic, adrenal, hepatocellular carcinoma and a considerable percentage of breast carcinomas. 99mTc-Sestamibi, a lipophilic cationic complex is a transport substrate for Pgp. In clinical studies of human neoplasms it was found that tumour uptake and clearance of this tracer correlate with Pgp expression and may be used for the phenotypic assessment of MDR. However, new tracers with better substrate specificity for Pgp and other drug transporters would greatly assist in optimising chemotherapeutic treatment and improving patient management by predicting tumour response to therapy and to assist in the development of antagonists, which may reverse or halt MDR. The aim of this project is therefore to develop PET and SPECT radiopharmaceuticals with improved affinity and selectivity for Pgp and MRP for the clinical evaluation of MDR in cancer patients. To optimise cellular transport characteristics, a number of chemical families that have been found to be substrates of Pgp and other drug efflux pumps, will be investigated. In the first instance, a series of drugs based on the flavonol natural product, Quercetin will be developed, screened for MDR and radiolabelled with PET and SPECT isotopes. Quercetin and related flavonol derivatives have been selected for this project because of their moderate to good affinity for Pgp. With the assistance of molecular modeling and in vitro studies, structural modification will be undertaken to improve the specificity and affinity for PgP. This generic structure also offers the flexibility to prepare a wide range of molecules that are readily suitable for halogenation with either Iodine-123 or F-18 for radiopharmaceutical development. Finally these phenolic type of molecules based on Quercetin are relatively less toxic than equivalent drugs. In this proposal an extensive research program is required to develop specific drugs for the different efflux pumps present in the body, which represent multi drug resistance. A successful outcome is critically dependent on the initial synthesis of a large number of compounds for screening. The combined effort of the three institutions will boost resources significantly to a critical level required to competitively produce successful outcomes in the project. Optimisation studies on derivatives of these flavonols will be made in parallel with the assistance of in vitro studies by measuring the binding of compounds to the ATP sites of Pgp. An extensive in vitro screening program has been established in Paris, prior to radiolabelling and in vivo evaluation. Structural optimisation and attachment of radionuclides to promising molecular targets will be explored using molecular modelling. Initially computational chemistry using Sybyl will be undertaken to develop a pharmacophore and to assist with the incorporation of the radionuclide in the appropriate position. In vivo evaluation will be undertaken in specific animal models both at the University of Tours in France as well as at the Sydney Cancer Centre in Australia. PET functional imaging studies may be undertaken on successful candidates at the SHFJ in Orsay, France whilst SPECT imaging will be undertaken in both Tours and in Sydney. In addition to intellectual property and potential commercial product(s), specific PET or SPECT radiopharmaceuticals can provide valuable information on the assessment of MDR in cancer patients through functional, non-invasive, imaging and therefore make significant contributions to the understanding of MDR. Scientific and clinical researchers from both countries identified the use of PET and SPECT functional imaging of MDR as a priority area of research. Finally the clear benefits to cancer patients include choice of treatment, with minimisation of ineffective drug treatments at an earlier stage, hence reduced drug side effects and discomfort to patients and improvements in their quality of life. There are also reduced health costs by avoiding expensive and ineffective drug treatments,
Domain organization of the monomeric form of the Tom70 mitochondrial import receptor
(Elsevier, 2009-05-22) Mills, RD; Trewhella, J; Qiu, TW; Welte, T; Ryan, TM; Hanley, TL; Knott, RB; Lithgow, T; Mulhern, TD
Tom70 is a mitochondrial protein import receptor composed of 11 tetratricopeptide repeats (TPRs). The first three TPRs form an N-terminal domain that recruits heat shock protein family chaperones, while the eight C-terminal TPRs form a domain that receives, from the bound chaperone, mitochondrial precursor proteins destined for import. Analytical Ultracentrifugation and solution small-angle X-ray scattering (SAXS) analysis characterized Tom70 as an elongated monomer. A model for the Tom70 monomer was proposed based on the alternate interpretation of the domain pairings observed in the crystal structure of the Tom70 dimer and refined against the SAXS data. In this "open" model of the Tom70 monomer, the chaperone- and precursor-binding sites are exposed and lay side by side oil one face of the molecule. Fluorescence anisotropy measurements indicated that monomeric Tom70 can bind both chaperone and precursor peptides and that chaperone peptide binding does not alter the affinity of Tom70 for the precursor peptide. SAXS Was unable to detect any shape change in Tom70 upon chaperone binding. However, molecular modeling indicated that chaperone binding is incompatible with Tom70 dimer formation. It is proposed that the Tom70 monomer is the functional unit mediating initial chaperone docking and precursor recognition. © 2009, Elsevier Ltd.
Effect of gamma-irradiation on the mechanical properties of carbon nanotube yarns
(Elsevier, 2011-11-01) Miao, M; Hawkins, S; Cai, JY; Gengenbach, TR; Knott, RB; Huynh, CP
Gamma-irradiation of carbon nanotube yarns in air has significantly improved the tensile strength and modulus of the yarns, presumably because of an increased interaction between the individual nanotubes. The improvement has been much greater for tightly structured yarns than for loosely structured yarns. Sonic pulse tests have also shown increased sound velocity and dynamic modulus in the carbon nanotube yarns as a result of gamma-irradiation treatment. X-ray photoelectron spectroscopic analyses on progenitor carbon nanotube forests show that gamma-irradiation treatment in air has dramatically increased the concentration of oxygen, for example as carboxyl groups, in the carbon nanotube assemblies in proportion to radiation dose, indicating that carbon nanotubes were oxidized under the ionizing effect of the gamma-irradiation. Such oxygen species are thought to contribute to the interaction between carbon nanotubes and thus to the improvement of carbon nanotube yarn mechanical properties. Crown Copyright (C) 2011 Published by Elsevier Ltd.
Effect of sol-gel encapsulation on lipase structure and function: a small angle neutron scattering study
(Springer, 2005-01) Rodgers, LE; Holden, PJ; Knott, RB; Finnie, KS; Bartlett, JR; Foster, LJR
The application of small angle neutron scattering (SANS) to the characterisation of sol–gel hosts containing biomolecules offers the opportunity to explore the relationship between gel structure and catalyst. A model system involving the immobilisation of Candida antarctica lipase B (CALB) was investigated. Gels were produced by fluoride-catalysed hydrolysis of fixed ratios of tetramethylorthosilicate (TMOS) and methyltrimethoxysilane (MTMS). Phase separation between the enzyme and the evolving sol–gel matrix was minimised by incorporating glycerol into the sol–gel precursor solution. The potential stabilising effect of the NaF catalyst upon the enzyme was also investigated. Scattering studies were conducted on both immobilised lipase, and lipase in free solution. Scattering studies on free enzyme provided evidence of multiple populations of enzyme aggregates and showed that choice of solvent affected the degree of aggregation. Both NaF and glycerol affected neutron scattering, indicating changes in lipase conformation. Increasing glycerol concentration increased the degree of aggregation and produced differences in solvent packing on the surface of protein molecules. Initial evidence from SANS data indicated that the presence of the enzyme during gel formation conferred structural changes on the gel matrix. Modelling the effect of sol–gel encapsulation on lipase requires comparison of data from free enzyme to the immobilised form. Removal of the enzyme from the sol–gel structure, post gelation, is necessary to better characterise the modified matrix. This methodological problem will be the subject of future investigations. © 2005, Springer.
Effects of crowding and environment on the evolution of conformational ensembles of the multi-stimuli-responsive intrinsically disordered protein, Rec1-resilin: a small-angle scattering investigation
(American Chemical Society, 2016-06-09) Balu, R; Mata, JP; Knott, RB; Elvin, CM; Hill, AJ; Choudhury, NR; Dutta, NK
In this study, we explore the overall structural ensembles and transitions of a biomimetic, multi-stimuli-responsive, intrinsically disordered protein (IDP), Rec1-resilin. The structural transition of Rec1-resilin with change in molecular crowding and environment is evaluated using small-angle neutron scattering and small-angle X-ray scattering. The quantitative analyses of the experimental scattering data using a combination of computational models allowed comprehensive description of the structural evolution, organization, and conformational ensembles of Rec1-resilin in response to the changes in concentration, pH, and temperature. Rec1-resilin in uncrowded solutions demonstrates the equilibrium intrinsic structure quality of an IDP with radius of gyration Rg ∼ 5 nm, and a scattering function for the triaxial ellipsoidal model best fit the experimental dataset. On crowding (increase in concentration >10 wt %), Rec1-resilin molecules exert intermolecular repulsive force of interaction, the Rg value reduces with a progressive increase in concentration, and molecular chains transform from a Gaussian coil to a fully swollen coil. It is also revealed that the structural organization of Rec1-resilin dynamically transforms from a rod (pH 2) to coil (pH 4.8) and to globular (pH 12) as a function of pH. The findings further support the temperature-triggered dual-phase-transition behavior of Rec1-resilin, exhibiting rod-shaped structural organization below the upper critical solution temperature (∼4 °C) and a large but compact structure above the lower critical solution temperature (∼75 °C). This work attempted to correlate unusual responsiveness of Rec1-resilin to the evolution of conformational ensembles. © 2016 American Chemical Society
Effects of precursor solution aging and other parameters on synthesis of ordered mesoporous titania powders
(American Chemical Society, 2015-03-11) Veliscek-Carolan, J; Knott, RB; Hanley, TL
Evaporation-induced self-assembly (EISA) of ordered mesoporous titania powders using block copolymer templates Brij 58 and F127 has been studied as a function of the precursor solution composition and age as well as the evaporation conditions. Small-angle X-ray scattering was used to monitor the degree of order in the mesoporous structure of materials synthesized under these varying conditions. Also, for the first time, the time-dependent formation of Ti structures in precursor solutions and the effect of those structures on the creation of mesostructural order have been demonstrated. The interactions of the Ti precursor with Brij 58 and F127 were investigated and showed that the different templates caused formation of Ti oligomers of unique sizes and structures. Precursor solution composition and evaporation conditions were also shown to affect the order and stability of the mesoporous titania produced. Overall, this systematic study has provided fundamental insights into the synthesis conditions that maximize the degree of order and thermal stability of the final materials. These “optimal” conditions are highly dependent on the choice of template. As a result of this improved understanding, the synthesis of ordered mesoporous titania powders using the block copolymer F127 as a template has been achieved without the use of stabilizing agents for the first time. © 2015 American Chemical Society
Effects of selected process parameters on the morphology of poly(ethylene terephthalate) preforms and bottles
(Wiley-Blackwell, 2007-10-05) Hanley, TL; Sutton, D; Karatchevtseva, I; Cookson, DJ; Burford, RP; Knott, RB
Small-angle X-ray scattering (SAXS) studies and polarized optical microscopy were undertaken to explore possible morphological explanations for the poor mechanical strength in the petaloid bases of poly(ethylene terephthalate) bottles. With a standard commercial production line, one set of injection-molded preforms was over-packed by 1.1 wt % to investigate the effect on the molecular morphology with respect to a set of control samples. Both sets of preforms showed highly crystalline and oriented areas corresponding to the injection gate region. The main body of the control preform was amorphous, and although the overpacked preform was essentially amorphous, there was some evidence for weak crystallinity. The SAXS patterns of the bottle petaloid base blown from the corresponding preforms produced similar SAXS patterns for overpacked and control bottle bases, indicating that the commercial process is robust at least to this degree of overpacking. Optical microscopy showed detailed crystalline features around the gate region and thin crystalline layers sandwiched between a quenched skin layer in direct contact with the cold mold walls and the main flow of material into the mold. © 2007, Wiley-Blackwell.
Encapsulation of protein in silica matrices: structural evolution on the molecular and nanoscales.
(American Chemical Society, 2010-01-19) Gao, Y; Heinemann, A; Knott, RB; Bartlett, JR
The immobilization of biological species such its proteins and enzymes in sol-gel hosts is currently an area of intense research activity. However, the majority of these studies have been directed toward investigating the biological activity or physicochemical properties of the encapsulated species, with much less attention having been directed toward the effect of proteins on the structural evolution of the sol-gel matrix. This study investigates the structural evolution of sol-gel matrices in the presence of a model protein, bovine serum albumin (BSA). The sol-gel matrices were produced via the NaF-catalyzed hydrolysis of a mixture of tetramethyoxysilane (TMOS) and methyltrimethoxysilane (MTMS), yielding nanohybrid matrices with controlled pore sizes, pore volumes, and surface chemistry. The structural evolution of the matrix was investigated using a complementary suite of techniques, including solid-state Si-29 NMR, FTIR, SANS contrast variation, and N-2 sorption. A novel approach was developed to model the SANS data, to extract key structural parameters. The results indicated that the structural evolution of the matrices was modulated by a series of complex interactions between the enzyme and the evolving sol-gel nanohybrid: On the molecular scale, increasing BSA content led to an associated increase in both the abundance of linear Si-O-Si species (FTIR) and the Qn network connectivity (Si-29 NMR). However, only minor changes in the connectivity of the evolving Tn network were evident with varying BSA content. The selective role of the protein in these systems, where the approach of the methylated monomer to the vicinity of the protein's surface is presumably impeded by the hydrophobicity of the monomer, will be discussed. On the nanoscale, N-2 sorption data were consistent with an initial increase in the mesopore volume and surface area at low BSA loadings, followed by a subsequent monotonic decrease with increasing BSA content. In contrast, no such trends were evident in the in situ SANS data obtained from these samples, suggesting that modulation of the evolving network structure of the silica matrix by BSA during condensation prevents collapse of the nanoscale gel structure during freeze-drying. This latter comparison reflects the important role of in situ techniques such as small angle scattering (which can be used to study both open and closed porosity and probe nanostructure on length scales from similar to 1 nm to > 100 nm) in investigating such complex, multicomponent systems, and techniques for modeling such data in sol-gel systems will be discussed. © 2010, American Chemical Society
Enhanced mechanical performance of CNT/polymer composite yarns by γ-irradiation
(Springer Nature, 2014-02-22) Cai, JY; Min, J; Miao, MH; Church, JS; McDonnell, J; Knott, RB; Hawkins, S; Huynh, C
Multiwall carbon nanotube (CNT) spun yarns were subjected to γ-irradiation in an oxygen rich environment, followed by the application of epoxy to form CNT/epoxy composite yarns with a high CNT fraction. The method for fabrication of the CNT/polymer composite yarns was presented, and the effect of γ-irradiation on the mechanical performance of the pure CNT spun yarns and their epoxy composite yarns were studied. The γ-irradiated CNT yarns were also characterized by X-ray Photoelectron Spectroscopy and Raman spectroscopy. The results of this study have demonstrated that the γ-irradiation is an effective micro-engineering tool to improve mechanical properties of the CNT spun yarn and its epoxy composite yarn. © 2020 Springer Nature Switzerland AG
Environment-induced self-assembly in phase separated block copolymer systems
(The Bragg Institute, Australian Nuclear Science and Technology Organisation, 2005-11-27) Dutta, NK; Thompson, S; Choudhury, NR; Knott, RB
Polymer chain sequence with different repeating unit and thermodynamic incompatibility between the segments can be chemically linked together through covalent bonds to form block copolymers of unique ordered microstructure and characteristics. Such block copolymers are characterized by fluid-like disorder ion the molecular scale and a high degree of morphological order at longer length scales, resulting in complex equilibrium phase behaviors, giving rise to a large variety of microdomain structures. A specific block copolymer may be optimum nanomaterial, either for their intrinsic properties as self-organized assemblies; or could be used as a strategy to template the organization of the desired inorganic. semi-conducting, metallic or biologically relevant materials into particles, nano planes, wires, or spheres within the polymer matrix. The amphiphilic block copolymers that self-assemble in selective solvents are also of significant scientific interest and of extensive importance in the field of controlled drug delivery systems, detergents, paints, cosmetics, oil recovery.. The situation is versatile and complicated since for a block copolymer system a solvent that is good for one block may be neutral, slightly selective, or strongly selective, or a non-solvent for the other block/ls. in multiblock copolymer with selective solvents the dramatic expansion of parameter space poses both experimental and theoretical challenges; and there has been very limited systematic research on the environment-induced self-organization of the phase behavior of triblock copolymer. ln this research work the effect of selective solvent and temperature on the phase behavior of a polystyrene-b-(ethylene-co-butylene)-b-styrene triblock copolymer (SEBS) are presented. We examine the adaptive nature of the ordering in asymmetric block copolymers, using a small angle neutron scattering techniques (SANS). The effect of solvent selectivity and temperature on the evolution of the scattering pattern and trends of the interference maximum in the lovv q (structure factor related to interdomain interference and indicates relatively higher level of ordering of the micelle cores) and high q regimes (form factor related to the contribution of the smaller intradomain distances) has been monitored. The organizational behavior has also been confirmed using Atomic force microscopy (AFM), transmission electron microscopy (TEM) and rheolgical investigation. Morphological evolution of the self-assembled phase behavior of such polymer with the thermodynamic selectivity of solvent, temperature, heat treatment, and time will been discussed in detail. © The Authors
Environment-induced self-assembly in phase separated block copolymer systems: a SANS investigation
(Elsevier B. V., 2006-11-15) Dutta, NK; Thompson, S; Choudhury, NR; Knott, RB
In this research, we examine the effect of non-selective solvent on the large-scale mesoscopic ordering in asymmetric block copolymers, poly(styrene-block-ethylene/butylene-block-styrene) (SEBS) using small angle neutron scattering technique (SANS). SANS measurements were carried out over a wide range of concentrations and temperatures. Evolution of the self-assembled phase morphology in such polymer with the thermodynamic selectivity of solvent, temperature and concentration has been discussed. Correlation between morphology and thermorheological behavior of the gels has also been established. © 2006 Elsevier B.V.
Formation of liquid-crystalline structures in the bile salt–chitosan system and triggered release from lamellar phase bile salt–chitosan capsules
(American Chemical Society, 2014-07-22) Tangso, KJ; Lindberg, S; Hartley, PG; Knott, RB; Spicer, P; Boyd, BJ
Nanostructured capsules comprised of the anionic bile salt, sodium taurodeoxycholate (STDC), and the biocompatible cationic polymer, chitosan, were prepared to assess their potential as novel tailored release nanomaterials. For comparison, a previously studied system, sodium dodecyl sulfate (SDS), and polydiallyldimethylammonium chloride (polyDADMAC) was also investigated. Crossed-polarizing light microscopy (CPLM) and small-angle X-ray scattering (SAXS) identified the presence of lamellar and hexagonal phase at the surfactant–polymer interface of the respective systems. The hydrophobic and electrostatic interactions between the oppositely charged components were studied by varying temperature and salt concentration, respectively, and were found to influence the liquid-crystalline nanostructure formed. The hexagonal phase persisted at high temperatures, however the lamellar phase structure was lost above ca. 45 °C. Both mesophases were found to dissociate upon addition of 4% NaCl solution. The rate of release of the model hydrophilic drug, Rhodamine B (RhB), from the lamellar phase significantly increased in response to changes in the solution conditions studied, suggesting that modulating the drug release from these bile salt–chitosan capsules is readily achieved. In contrast, release from the hexagonal phase capsules had no appreciable response to the stimuli applied. These findings provide a platform for these oppositely charged surfactant and polymer systems to function as stimuli-responsive or sustained-release drug delivery systems. © 2014, American Chemical Society.
A genetically engineered protein responsive to multiple stimuli
(Wiley-Blackwell, 2011-04-06) Dutta, NK; Truong, MY; Mayavan, S; Choudhury, NR; Elvin, CM; Kim, M; Knott, RB; Nairn, KM; Hill, AJ
Smart protein: Careful design can yield novel biologically inspired materials that display advanced responsive behavior. A genetically engineered elastic protein displays both a lower and an upper critical solution temperature (LCST and UCST, see picture), and its photophysical behavior depends on solution pH value.
Guanidine hydrochloride denaturation of dopamine-induced α-synuclein oligomers: a small-angle x-ray scattering study
(Wiley Online Library, 2013-06-4) Pham, CLL; Kirby, N; Wood, K; Ryan, T; Roberts, B; Sokolova, AV; Barnham, KJ; Masters, CL; Knott, RB; Cappai, R; Curtain, CC; Rekas, A
Alpha-synuclein (α-syn) forms the amyloid-containing Lewy bodies found in the brain in Parkinson's disease. The neurotransmitter dopamine (DA) reacts with α-syn to form SDS-resistant soluble, non-amyloid, and melanin-containing oligomers. Their toxicity is debated, as is the nature of their structure and their relation to amyloid-forming conformers of α-syn. The small-angle X-ray scattering technique in combination with modeling by the ensemble optimization method showed that the un-reacted native protein populated three broad classes of conformer, while reaction with DA gave a restricted ensemble range suggesting that the rigid melanin molecule played an important part in their structure. We found that 6 M guanidine hydrochloride did not dissociate α-syn DA-reacted dimers and trimers, suggesting covalent linkages. The pathological significance of covalent association is that if they are non-toxic, the oligomers would act as a sink for toxic excess DA and α-syn; if toxic, their stability could enhance their toxicity. We argue it is essential, therefore, to resolve the question of whether they are toxic or not. © 2013,Wiley Periodicals, Inc.
In situ SAXS studies of the formation of sodium jarosite
(Wiley-Blackwell, 2013-07-01) Brand, HEA; Scarlett, NVY; Grey, IE; Knott, RB; Kirby, N
This paper reports the results of time-resolved synchrotron small-angle scattering and powder diffraction experiments where natrojarosites were synthesized in situ in order to observe the species produced at the earliest stages of nucleation. The sample temperatures were 333, 353 and 368 K. These compounds were synthesized by co-precipitation from solution on the Small and Wide Angle Scattering and Powder Diffraction beamlines at the Australian Synchrotron. Scattering data were collected continuously throughout the syntheses. The results presented here show that the first particles to form in solution appear to be amorphous and nucleate on the walls of the reaction vessel. Crucially, there is a single nucleation event which forms particles with an elliptical disc morphology which then grow uniformly before natrojarosite crystallization is observed in complementary powder diffraction data. This nucleation event may represent the key to controlling the growth of jarosites in industrial and environmental settings. © 2013, Wiley-Blackwell.

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