201 results found
Ja'afar F, Leow CH, Garbin V, et al., 2015, Surface Charge Measurement of SonoVue, Definity and Optison: A Comparison of Laser Doppler Electrophoresis and Micro-Electrophoresis, Ultrasound in Medicine and Biology, Vol: 41, Pages: 2990-3000, ISSN: 0301-5629
Microbubble (MB) contrast-enhanced ultrasonography is a promising tool for targeted molecular imaging. It is important to determine the MB surface charge accurately as it affects the MB interactions with cell membranes. In this article, we report the surface charge measurement of SonoVue, Definity and Optison. We compare the performance of the widely used laser Doppler electrophoresis with an in-house micro-electrophoresis system. By optically tracking MB electrophoretic velocity in a microchannel, we determined the zeta potentials of MB samples. Using micro-electrophoresis, we obtained zeta potential values for SonoVue, Definity and Optison of −28.3, −4.2 and −9.5 mV, with relative standard deviations of 5%, 48% and 8%, respectively. In comparison, laser Doppler electrophoresis gave −8.7, +0.7 and +15.8 mV with relative standard deviations of 330%, 29,000% and 130%, respectively. We found that the reliability of laser Doppler electrophoresis is compromised by MB buoyancy. Micro-electrophoresis determined zeta potential values with a 10-fold improvement in relative standard deviation.
Pommella A, Brooks NJ, Seddon JM, et al., 2015, Selective flow-induced vesicle rupture to sort by membrane mechanical properties, Scientific Reports, Vol: 5, ISSN: 2045-2322
Yeh JS-M, Sennoga CA, McConnell E, et al., 2015, A targeting microbubble for ultrasound molecular imaging, PLoS ONE, Vol: 10, ISSN: 1932-6203
Seddon JM, Brooks NJ, Ces O, et al., 2015, Lipid bicontinuous cubic phases: effects of chain-branching and hydrostatic pressure, 10th European-Biophysical-Societies-Association (EBSA) European Biophysics Congress, Publisher: SPRINGER, Pages: S187-S187, ISSN: 0175-7571
Gater D, Tyler A, Seddon JM, et al., 2015, The liquid ordered phase of cholesterol-dipalmitoylglycerol, EUROPEAN BIOPHYSICS JOURNAL WITH BIOPHYSICS LETTERS, Vol: 44, Pages: S112-S112, ISSN: 0175-7571
McCarthy NL, Ces O, Law RV, et al., 2015, Separation of liquid domains in model membranes induced with high hydrostatic pressure, EUROPEAN BIOPHYSICS JOURNAL WITH BIOPHYSICS LETTERS, Vol: 44, Pages: S115-S115, ISSN: 0175-7571
Barriga H, Tyler A, McCarthy NL, et al., 2015, Engineering swollen bicontinuous cubic phases and cubosomes; a new generation of artificial cells, EUROPEAN BIOPHYSICS JOURNAL WITH BIOPHYSICS LETTERS, Vol: 44, Pages: S109-S109, ISSN: 0175-7571
McCarthy NLC, Ces O, Law RV, et al., 2015, Separation of liquid domains in model membranes induced with high hydrostatic pressure, Chemical Communications, Vol: 51, Pages: 8675-8678, ISSN: 1364-548X
We have imaged the formation of membrane microdomains immediately after their induction using a novel technology platform coupling high hydrostatic pressure to fluorescence microscopy. After formation, the ordered domains are small and highly dynamic. This will enhance links between model lipid assemblies and dynamic processes in cellular membranes.
Tang T-YD, Brooks NJ, Ces O, et al., 2015, Structural studies of the lamellar to bicontinuous gyroid cubic (Q(II)(G)) phase transitions under limited hydration conditions, SOFT MATTER, Vol: 11, Pages: 1991-1997, ISSN: 1744-683X
Tyler AII, Barriga HMG, Parsons ES, et al., 2015, Electrostatic swelling of bicontinuous cubic lipid phases, Soft Matter, Vol: 11, Pages: 3279-3286, ISSN: 1744-6848
Lipid bicontinuous cubic phases have attracted enormous interest as bio-compatible scaffolds for use in a wide range of applications including membrane protein crystallisation, drug delivery and biosensing. One of the major bottlenecks that has hindered exploitation of these structures is an inability to create targeted highly swollen bicontinuous cubic structures with large and tunable pore sizes. In contrast, cubic structures found in-vivo have periodicities approaching the micron scale. We have been able to engineer and control highly swollen bicontinuous cubic phases of spacegroup Im3m containing only lipids by a) increasing the bilayer stiffness by adding cholesterol and b) inducing electrostatic repulsion across the water channels by addition of anionic lipids to monoolein. By controlling the composition of the ternary mixtures we have been able to achieve lattice parameters up to 470 Å, which is 5 times that observed in pure monoolein and nearly twice the size of any lipidic cubic phase reported previously. These lattice parameters significantly exceed the predicted maximum swelling for bicontinuous cubic lipid structures, which suggest that thermal fluctuations should destroy such phases for lattice parameters larger than 300 Å.
Barriga HMG, Parsons ES, McCarthy NLC, et al., 2015, Pressure-Temperature Phase Behavior of Mixtures of Natural Sphingomyelin and Ceramide Extracts, Langmuir, Vol: 31, Pages: 3678-3686, ISSN: 1520-5827
Barriga HMG, Tyler AII, McCarthy NLC, et al., 2015, Temperature and pressure tuneable swollen bicontinuous cubic phases approaching nature's length scales, SOFT MATTER, Vol: 11, Pages: 600-607, ISSN: 1744-683X
Zhang Y, Lervik A, Seddon J, et al., 2015, A coarse-grained molecular dynamics investigation of the phase behavior of DPPC/cholesterol mixtures, CHEMISTRY AND PHYSICS OF LIPIDS, Vol: 185, Pages: 88-98, ISSN: 0009-3084
Elani Y, Purushothaman S, Booth PJ, et al., 2015, Measurements of the effect of membrane asymmetry on the mechanical properties of lipid bilayers, CHEMICAL COMMUNICATIONS, Vol: 51, Pages: 6976-6979, ISSN: 1359-7345
Tyler AII, Law RV, Seddon JM, 2015, X-ray diffraction of lipid model membranes., Methods Mol Biol, Vol: 1232, Pages: 199-225
In this chapter the use of X-ray diffraction to study the structure of lyotropic phases and lipid model membranes is described. Determination of the phase symmetry and lattice parameters from small-angle X-ray scattering (SAXS), and of the nature of the hydrocarbon chain packing from wide-angle X-ray scattering (WAXS), are discussed. Methods by which the sign of the interfacial curvature of non-lamellar phases may be determined are then presented. Finally, the calculation of electron density profiles from the intensities of the observed Bragg peaks is described, for the lamellar phase and for the inverse hexagonal phase.
In this chapter we describe the use of solid state nuclear magnetic spectroscopy to study the structure of lyotropic phases and lipid model membranes and show its ability to probe, site specifically, at a sub-Ångstrom resolution. Here, we demonstrate the immense versatility of the technique and its ability to provide information on the different liquid crystalline phases present. A multinuclear for example (31)P, (1)H, and (13)C approach is able to elucidate both the structure and dynamics over a wide variety of timescales. This coupled with a non-perturbing label (2)H is able to provide information such as the order parameters for a wide variety of different liquid phases.
Karamdad K, Law RV, Seddon JM, et al., 2014, Preparation and mechanical characterisation of giant unilamellar vesicles by a microfluidic method, Lab on a Chip, ISSN: 1473-0197
Giant unilamellar vesicles (GUVs) have a wide range of applications in biology and synthetic biology. As a result, new approaches for constructing GUVs using microfluidic techniques are emerging but there are still significant shortcomings in the control of fundamental vesicle structural parameters such as size, lamellarity, membrane composition and internal contents. We have developed a novel microfluidic platform to generate compositionally-controlled GUVs. Water-in-oil (W/O) droplets formed in a lipid-containing oil flow are transferred across an oil- water interface, facilitating the self-assembly of a phospholipid bilayer. In addition, for the first time we have studied the mechanical properties of the resultant lipid bilayers of the microfluidic GUVs. Using fluctuation analysis we were able to calculate the values for bending rigidity of giant vesicles assembled on chip and demonstrate that these correlate strongly with those of traditional low throughput strategies such as electroformation.
Brooks NJ, Seddon JM, 2014, High Pressure X-ray Studies of Lipid Membranes and Lipid Phase Transitions, Zeitschrift für Physikalische Chemie, Vol: 228, Pages: 987-1004, ISSN: 0942-9352
Hydrostatic pressure has dramatic effects on biomembrane structure and stability and is a key thermodynamic parameter in the context of the biology of deep sea organisms. Furthermore, high-pressure and pressure-jump studies are very useful tools in biophysics and biotechnology, where they can be used to study the mechanism and kinetics of lipid phase transitions, biomolecular transforma- tions, and protein folding/unfolding. Here, we first give an overview of the tech- nology currently available for X-ray scattering studies of soft matter systems under pressure. We then illustrate the use of this technology to study a variety of lipid membrane systems.
Carreras P, Elani Y, Law R, et al., A droplet trapping microfluidic device for the study of mass-transport across droplet interface bilayers, MicroTAS 2014
Carreras P, Law RV, Brooks NJ, et al., 2014, Microfluidic generation of droplet interface bilayer networks incorporating real-time size sorting in linear and non-linear configurations, Biomicrofluidics, Vol: 8, ISSN: 1932-1058
In this study, a novel droplet based microfluidic method for the generation of different sized droplet interface bilayers is reported. A microfluidic platform was designed, which allows the generation and packing of picoliter lipid coated water droplets. Droplets were generated by hydrodynamic focusing coupled with selective transport along grooves according to their size. A trapping structure at the end of the groove and a fine control of the flow pressures allowed for the droplets to be successfully trapped and aligned on demand. This technology facilitates the fine control of droplet size production as well as the generation of extended networks from a variety of lipids including 1,2-diphytanoyl-sn-glycero-3- phosphocholine and 1,2-dioleoyl-sn-glycero-3-phosphocholine in linear and non- linear configurations, which is vital to the application of Droplet Interface Bilayers to biological network construction on-chip.
Sennoga CA, Seddon JM, Frueh JA, et al., 2014, DYNAMICS OF TARGETED MICROBUBBLE ADHESION UNDER PULSATILE COMPARED WITH STEADY FLOW, ULTRASOUND IN MEDICINE AND BIOLOGY, Vol: 40, Pages: 2445-2457, ISSN: 0301-5629
Hamid HAA, Hashim R, Seddon JM, et al., 2014, Lyotropic phase behaviour and structural parameters of monosaccharide and disaccharide guerbet branched-chain β-D-glycosides, Advanced Materials Research, Vol: 895, Pages: 111-115, ISSN: 1022-6680
The phase behaviour and self-assembly structural parameters of a pair of monosaccharide and disaccharide Guerbet branched-chain β-D-glycosides, namely 2-octyldodecyl β-D-glucoside (β-Glc- C12C8) and 2-octyldodecyl β-D-maltoside (β-Mal- C12C8), have been studied by means of optical polarizing microscopy (OPM) and small-angle X-ray diffraction at room temperature (25°C). These compounds are sugar-based glycolipid surfactants having a total chain length of C20, and differ based on the increasing number of hydroxyl groups of the sugar headgroup (glucose and maltose). The repeat spacings obtained by X-ray diffraction as a function of water content have been used to determine the limiting hydration for the two glycosides. At room temperature, β-Glc-12C8 and β- Mal- C12C8 have limiting hydrations of 22 wt% and 25 wt%, corresponding to 8 - 10 and 10 - 12 water molecules per glycoside, respectively. At all water contents between 5 and 29 wt % water, these compounds adopt inverse hexagonal (HII) or fluid lamellar (Lα) phases. The structural parameters of these phases have been determined from the diffraction data, from the X-ray repeat spacings, densities and concentration of the glycosides. © (2014) Trans Tech Publications, Switzerland.
Tang T-YD, Seddon AM, Jeworrek C, et al., 2014, The effects of pressure and temperature on the energetics and pivotal surface in a monoacylglycerol/water gyroid inverse bicontinuous cubic phase, SOFT MATTER, Vol: 10, Pages: 3009-3015, ISSN: 1744-683X
Gordon VD, Beales PA, Shearman GC, et al., 2014, Solid-Like Domains in Mixed Lipid Bilayers. Effect of Membrane Lamellarity and Transition Pathway, Vol: 20, Pages: 137-154, ISSN: 1554-4516
We present optical observations of phase separation in mixed model membranes in the form of giant unilamellar vesicles. These observations are compared to the phase behavior of lipid mixtures, which we determined by X-ray scattering and differential scanning calorimetry or extracted from the existing literature. The domain properties are affected not only by the bulk phase behavior but also by the membrane lamellarity and phase transition pathways. These observations have important implications for how phase behavior determined by bulk methods using dense, multilamellar lipid bilayers are linked to phase separation in giant, unilamellar lipid bilayers as observed by microscopy. © 2014 Elsevier Inc.
Cook AG, Martinez-Felipe A, Brooks NJ, et al., 2013, New insights into the transitional behaviour of methyl-6-O-(n-dodecanoyl)-alpha-D-glucopyranoside using variable temperature FTIR spectroscopy and X-ray diffraction, LIQUID CRYSTALS, Vol: 40, Pages: 1817-1827, ISSN: 0267-8292
Zahid NI, Conn CE, Brooks NJ, et al., 2013, Investigation of the Effect of Sugar Stereochemistry on Biologically Relevant Lyotropic Phases from Branched-Chain Synthetic Glycolipids by Small-Angle X-Ray Scattering, Langmuir
Synthetic branched-chain glycolipids are suitable as model systems to understand biological cell membranes, particularly since certain natural lipids possess chain branching. Herein, four branched-chain glycopyranosides namely 2-hexyl-decyl-α-D-glucopyranoside (α-Glc-OC10C6), 2-hexyl-decyl-β-D-glucopyranoside (β-Glc-OC10C6), 2-hexyl-decyl-α-D-galactopyranoside (α-Gal-OC10C6) and 2-hexyl-decyl-β-D-galactopyranoside (β-Gal-OC10C6) with a total alkyl chain length of 16 carbon atoms have been synthesized and their phase behaviour studied. The partial binary phase diagrams of these non-ionic surfactants in water were investigated by optical polarizing microscopy (OPM) and small-angle X-ray scattering (SAXS). The introduction of chain branching in the hydrocarbon chain region is shown to result in the formation of inverse structures such as the inverse hexagonal and inverse bicontinuous cubic phases. Comparison of the four compounds showed that they exhibited different polymorphism, especially in the thermotropic state, due to contributions from anomeric and epimeric effects according to their stereochemistry. The neat compound of α-Glc-OC10C6 exhibited a lamellar (Lα) phase whereas dry α-Gal-OC10C6formed an inverse bicontinuous cubic Ia3d (QIIG) phase. Both β-anomers of glucoside and galactoside adopted the inverse hexagonal phase (HII) in the dry state. Generally, in the presence of water, all four glycolipids formed inverse bicontinuous cubic Ia3d (QIIG) and Pn3m (QIID) phases over a wide temperature and concentration range. The formation of inverse non-lamellar phases by these Guerbet branched-chain glycosides confirms their potential as materials for novel biotechnological applications such as drug-delivery and crystallization of membrane proteins.
Miller D, Booth PJ, Seddon JM, et al., 2013, Protocell design through modular compartmentalization, JOURNAL OF THE ROYAL SOCIETY INTERFACE, Vol: 10, ISSN: 1742-5689
Brooks N, Barriga H, McCarthy N, et al., 2013, Dynamic membrane structures at high pressure, 9th European-Biophysical-Societies-Association Congress, Publisher: SPRINGER, Pages: S118-S118, ISSN: 0175-7571
Tyler AII, Shearman GC, Parsons ES, et al., 2013, Tuning curvature in inverse micellar and bicontinuous cubic phases, 9th European-Biophysical-Societies-Association Congress, Publisher: SPRINGER, Pages: S140-S140, ISSN: 0175-7571
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