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154 results on '"Seddon, Annela M."'

1. Protein-Polymer Mixtures in the Colloid Limit: Aggregation, Sedimentation and Crystallization

Author

Cheng, Rui, Li, Jingwen, de Anda, Ioatzin Ríos, Taylor, Thomas W. C., Faers, Malcolm A., Anderson, J. L. Ross, Seddon, Annela M., and Royall, C. Patrick

Subjects
Condensed Matter - Soft Condensed Matter, Condensed Matter - Statistical Mechanics, Physics - Biological Physics
Abstract

While proteins have been treated as particles with a spherically symmetric interaction, of course in reality the situation is rather more complex. A simple step towards higher complexity is to treat the proteins as non--spherical particles and that is the approach we pursue here. We investigate the phase behavior of enhanced green fluorescent protein (eGFP) under the addition of a non--adsorbing polymer, polyethylene glycol (PEG). From small angle x-ray scattering we infer that the eGFP undergoes dimerization and we treat the dimers as spherocylinders with aspect ratio $L/D-1 = 1.05$. Despite the complex nature of the proteins, we find that the phase behaviour is similar to that of hard spherocylinders with ideal polymer depletant, exhibiting aggregation and, in a small region of the phase diagram, crystallization. By comparing our measurements of the onset of aggregation with predictions for hard colloids and ideal polymers [S.V. Savenko and M. Dijkstra, J. Chem. Phys 124, 234902 (2006) and F. lo Verso et al., Phys. Rev. E 73, 061407 (2006)] we find good agreement, which suggests that the eGFP proteins are consistent with hard spherocylinders and ideal polymer., Comment: 12 pages

Published
2021
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2. Opposed flow focusing: evidence of a second order jetting transition

Author

Dong, Jun, Meissner, Max, Eggers, Jens, Seddon, Annela M., and Royall, C. Patrick

Subjects
Condensed Matter - Soft Condensed Matter
Abstract

We propose a novel microfluidic "opposed-flow" geometry in which the continuous fluid phase is fed into a junction in a direction opposite the dispersed phase. This pulls out the dispersed phase into a micron-sized jet, which decays into micron-sized droplets. As the driving pressure is tuned to a critical value, the jet radius vanishes as a power law down to sizes below 1 $\mu$m. By contrast, the conventional "coflowing" junction leads to a first order jetting transition, in which the jet disappears at a finite radius of several $\mu$m, to give way to a "dripping" state, resulting in much larger droplets. We demonstrate the effectiveness of our method by producing the first microfluidic silicone oil emulsions with a sub micron particle radius, and utilize these droplets to produce colloidal clusters.

Published
2018

3. Oil-in-water microfluidics on the colloidal scale: new routes to self-assembly and glassy packings

Author

Meissner, Max, Dong, Jun, Eggers, Jens, Seddon, Annela M., and Royall, C. Patrick

Subjects
Condensed Matter - Soft Condensed Matter
Abstract

We have developed Norland Optical Adhesive (NOA) flow focusing devices, making use of the excellent solvent compatibility and surface properties of NOA to generate micron scale oil-in-water emulsions with polydispersities as low as 5%. While current work on microfluidic oil-in-water emulsification largely concerns the production of droplets with sizes on the order of 10s of micrometres, large enough that Brownian motion is negligible, our NOA devices can produce droplets with radii ranging from 2 {\mu}m to 12 {\mu}m. To demonstrate the utility of these emulsions as colloidal model systems we produce fluorescently labelled polydimethylsiloxane droplets suitable for particle resolved studies with confocal microscopy. We analyse the structure of the resulting emulsion in 3D using coordinate tracking and the topological cluster classification and reveal a new mono-disperse thermal system., Comment: 8 pages, 6 figures. expanded figure 6, typographical changes, edited abstract for clarity, modified references

Published
2016
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4. Polymorphic protein phase transitions driven by surface anisotropy.

Author

Strofaldi, Alessandro, Quinn, Michelle K., Seddon, Annela M., and McManus, Jennifer J.

Subjects
PHASE transitions, CONDENSED matter, HOMOGENEOUS nucleation, PHASE separation, ANISOTROPY, PROTEINS
Abstract

Phase transitions of proteins are strongly influenced by surface chemical modifications or mutations. Human γD-crystallin (HGD) single-mutants have been extensively studied because they are associated with the onset of juvenile cataract. However, they have also provided a rich library of molecules to examine how specific inter-protein interactions direct protein assembly, providing new insights and valuable experimental data for coarse-grained patchy-particle models. Here, we demonstrate that the addition of new inter-protein interactions by mutagenesis is additive and increases the number and variety of condensed phases formed by proteins. When double mutations incorporating two specific single point mutations are made, the properties of both single mutations are retained in addition to the formation of a new condensed phase. We find that the HGD double-mutant P23VC110M self-assembles into spherical particles with retrograde solubility, orthorhombic crystals, and needle/plate shape crystals, while retaining the ability to undergo liquid–liquid phase separation. This rich polymorphism is only partially predicted by the experimental data on the constituent single mutants. We also report a previously un-characterized amorphous protein particle, with unique properties that differ from those of protein spherulites, protein particulates previously described. The particles we observe are amorphous, reversible with temperature, tens of microns in size, and perfectly spherical. When they are grown on pristine surfaces, they appear to form by homogeneous nucleation, making them unique, and we believe a new form of protein condensate. This work highlights the challenges in predicting protein behavior, which has frustrated rational assembly and crystallization but also provides rich data to develop new coarse-grained models to explain the observed polymorphism. [ABSTRACT FROM AUTHOR]

Published
2023
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15. Acoustic levitation with polarising optical microscopy (AL-POM): water uptake in a nanostructured atmospheric aerosol proxyElectronic supplementary information (ESI) available. See DOI: https://doi.org/10.1039/d3ea00083d

Author

Milsom, Adam, Squires, Adam M., Brasnett, Christopher, Sharratt, William N., Seddon, Annela M., and Pfrang, Christian

Abstract

Laboratory studies on levitated particles of atmospheric aerosol proxies have provided significant contributions to our understanding of aerosol processes. We present an experimental method combining acoustic levitation with polarising optical microscopy (AL-POM) to probe optically birefringent particles, such as the nanostructured surfactant atmospheric aerosol proxy studied here. Birefringent particles were subjected to a step increase in humidity. A decrease in birefringence was measured over time as a result of a nanostructure change, confirmed by complementary synchrotron X-ray scattering. A multi-layer water uptake model was created and fitted to the experimental data, revealing a water diffusion coefficient increase by ca.5–6 orders of magnitude upon phase transition. This has implications for the timescale of water uptake in surfactant-containing aerosols and their atmospheric lifetimes. This experimental setup has strong potential to be used in conjunction with other levitation methods and in different contexts concerning birefringent materials such as crystallisation.

Published
2023
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16. Surface functionalisation significantly changes the physical and electronic properties of carbon nano-dots† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c8nr03430c ‡ ‡The raw data supporting this article are archived in the University of Bristol's Research Data Storage Facility (DOI: 10.5523/bris.30s3i070zb0qv2tipisop5a1h4)

Author

Swift, Thomas A., Duchi, Marta, Hill, Stephen A., Benito-Alifonso, David, Harniman, Robert L., Sheikh, Sadiyah, Davis, Sean A., Seddon, Annela M., Whitney, Heather M., Galan, M. Carmen, and Oliver, Thomas A. A.

Subjects
carbohydrates (lipids), Chemistry, technology, industry, and agriculture, natural sciences
Abstract

The electronic structure of glycan functionalised carbon nano-dots is greatly affected by the choice of carbohydrate., Biomolecule functionalisation of carbon nano-dots (CDs) greatly enhances their biocompatibility and applicability, however, little is known about their molecular structure. Using an arsenal of spectroscopic and analytical techniques, we provide new insights into the physical and electronic structure of uncoated and glycan-functionalised CDs. Our studies reveal that surface functionalisation does not always result in a homogenous corona surrounding the core, and the choice of carbohydrate significantly affects the electronic structure of the surface CD states. Further, the average surface coverage of an ensemble of CDs can be probed via transient absorption spectroscopy. These findings have implications for CDs targeted at interactions with biological systems or local sensors.

Published
2018

19. Elongation rate and average length of amyloid fibrils in solution using isotope-labelled small-angle neutron scattering

Author

Eves, Ben J., primary, Doutch, James J., additional, Terry, Ann E., additional, Yin, Han, additional, Moulin, Martine, additional, Haertlein, Michael, additional, Forsyth, V. Trevor, additional, Flagmeier, Patrick, additional, Knowles, Tuomas P. J., additional, Dias, David M., additional, Lotze, Gudrun, additional, Seddon, Annela M., additional, and Squires, Adam M., additional

Published
2021
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24. Using chirality to influence supramolecular gelation

Author

McAulay, Kate, primary, Dietrich, Bart, additional, Su, Hao, additional, Scott, Michael T., additional, Rogers, Sarah, additional, Al-Hilaly, Youssra K., additional, Cui, Honggang, additional, Serpell, Louise C., additional, Seddon, Annela M., additional, Draper, Emily R., additional, and Adams, Dave J., additional

Published
2019
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27. P-Type Low-Molecular-Weight Hydrogelators

Author

Draper, Emily R., primary, Dietrich, Bart, additional, Brasnett, Christopher, additional, Sproules, Stephen, additional, McDonald, Tom O., additional, Seddon, Annela M., additional, and Adams, Dave J., additional

Published
2018
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30. Buffers may adversely affect model lipid membranes: a cautionary tale

Author

Peiro-Salvador, Teresa, Ces, Oscar, Templer, Richard H., and Seddon, Annela M.

Subjects
Elasticity -- Analysis, Lipid membranes -- Chemical properties, Lipid membranes -- Structure, Membrane proteins -- Chemical properties, Biological sciences, Chemistry
Abstract

Research studies related to effects of biological buffer molecules which interact with the headgroup region of the lipid to cause membrane softening are presented. The changes in the elastic properties of the membrane which are known to control membrane protein behavior could be applied to design assays that utilize membranes in the presence of buffers.

Published
2009

31. Simple host-guest chemistry to modulate the process of concentration and crystallization of membrane proteins by detergent capture in a microfluidic device

Author

Liang Li, Nachtergaele, Sigrid, Seddon, Annela M., Tereshko, Valentina, Ponomarenko, Nina, and Ismagilov, Rustem F.

Subjects
Crystallization -- Analysis, Detergents, Synthetic -- Chemical properties, Membrane proteins -- Chemical properties, Membrane proteins -- Structure, Chemistry
Abstract

A new approach is described where in the simple host-guest chemistry is used to modulate the process of concentration and crystallization of membrane proteins by detergent capture in a microfluidic device. The process is shown to also lead to a better modulation of the membrane protein crystallization.

Published
2008

33. Self-assembly of a functional oligo(aniline)-based amphiphile into helical conductive nanowires

Author

Bell, O. Alexander, Wu, Guanglu, Haataja, Johannes S., Brömmel, Felicitas, Fey, Natalie, Seddon, Annela M., Harniman, Robert L., Richardson, Robert M., Ikkala, Olli, Zhang, Xi, and Faul, Charl F. J.

Subjects
Redox-active materials, functional nanomaterials, Oligo(aniline)s, Conducting nanowires, Article
Abstract

A tetra(aniline)-based cationic amphiphile, TANI-NHC(O)C5H10N(CH3)3+Br– (TANI-PTAB) was synthesized, and its emeraldine base (EB) state was found to self-assemble into nanowires in aqueous solution. The observed self-assembly is described by an isodesmic model, as shown by temperature-dependent UV–vis investigations. Linear dichroism (LD) studies, combined with computational modeling using time-dependent density functional theory (TD-DFT), suggests that TANI-PTAB molecules are ordered in an antiparallel arrangement within nanowires, with the long axis of TANI-PTAB arranged perpendicular to the nanowire long axis. Addition of either S- or R- camphorsulfonic acid (CSA) to TANI-PTAB converted TANI to the emeraldine salt (ES), which retained the ability to form nanowires. Acid doping of TANI-PTAB had a profound effect on the nanowire morphology, as the CSA counterions’ chirality translated into helical twisting of the nanowires, as observed by circular dichroism (CD). Finally, the electrical conductivity of CSA-doped helical nanowire thin films processed from aqueous solution was 2.7 mS cm–1. The conductivity, control over self-assembled 1D structure and water-solubility demonstrate these materials’ promise as processable and addressable functional materials for molecular electronics, redox-controlled materials and sensing.

Published
2015

35. Control of Nanomaterial Self-Assembly in Ultrasonically Levitated Droplets

Author

Seddon, Annela M., Richardson, Sam J, Rastogi, Kunal, Plivelic, Tomás, Squires, Adam M., Pfrang, Christian, Seddon, Annela M., Richardson, Sam J, Rastogi, Kunal, Plivelic, Tomás, Squires, Adam M., and Pfrang, Christian

Abstract

We demonstrate that acoustic trapping can be used to levitate and manipulate droplets of soft matter, in particular, lyotropic mesophases formed from selfassembly of different surfactants and lipids, which can be analyzed in a contact-less manner by X-ray scattering in a controlled gas-phase environment. On the macroscopic length scale, the dimensions and the orientation of the particle are shaped by the ultrasonic field, while on the microscopic length scale the nanostructure can be controlled by varying the humidity of the atmosphere around the droplet. We demonstrate levitation and in situ phase transitions of micellar, hexagonal, bicontinuous cubic, and lamellar phases. Thetechnique opens up a wide range of new experimental approaches of fundamentalimportance for environmental, biological, and chemical research.

Published
2016

43. Engineering bicontinuous cubic structures at the nanoscale—the role of chain splay

Author

Kulkarni, Chandrashekhar V., Tang, Tsing-Young, Seddon, Annela M., Seddon, John M., Ces, Oscar, Templer, Richard H., Kulkarni, Chandrashekhar V., Tang, Tsing-Young, Seddon, Annela M., Seddon, John M., Ces, Oscar, and Templer, Richard H.

Abstract

Many amphiphile–water mixtures will self-assemble into three-dimensional soft condensed structures known as inverse bicontinuous cubic phases. These structures are found in nature and have applications in nanotechnology. Here we show that by systematically varying amphiphile chain splay, we are able to control the relative stability of the inverse bicontinuous phases in a homologous series of monoglycerides in a predictable manner. In particular, we demonstrate that decreasing chain splay leads to the appearance of the primitive bicontinuous cubic phase while increasing chain splay reduces the channel size of the remaining two bicontinuous phases and tends to destabilize them with respect to the more curved inverse micellar and inverse hexagonal phases. These observations are consistent with a model in which the energetic stability of these phases is principally governed by the competing demands for homogeneous interfacial curvature and uniform chain packing and points to straightforward rules for engineering these self-assembling nanostructures.

Published
2010

44. Evidence that membrane curvature distorts the tertiary structure of bacteriorhodopsin

Author

Kulkarni, Chandrashekhar V., Seddon, Annela M., Ces, Oscar, Templer, Richard H., Kulkarni, Chandrashekhar V., Seddon, Annela M., Ces, Oscar, and Templer, Richard H.

Abstract

The membrane protein bacteriorhodopsin (bR) can be reconstituted into the membrane of the lipid 1-monoolein (MO). This lipid forms a lyotropic liquid crystalline phase whose membrane has hyperbolic interfacial curvature. Using optical absorption spectroscopy and small angle X-ray scattering we have observed retinal unbinding from bR that is correlated with the degree of membrane interfacial curvature. The evidence suggests that bR is susceptible to membrane induced saddle splay for modest perturbations from equilibrium, but for more extreme distortions becomes stiff and resists membrane induced curvature.

Published
2010

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