Effects of Charge Double Layer and Colloidal Aggregation on the Isotropic−Nematic Transition of Protein Fibers in Water

Mezzenga, Raffaele; Jung, Jin-Mi; Adamčík, Jozef

doi:10.1021/la101636r

Cited by 74 publications

(97 citation statements)

References 26 publications

(43 reference statements)

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“…1a). At high concentrations (albeit much lower than in bulk systems 30,31 ), there is a coexistence of regions of highly anisotropic and isotropic tracer motion, indicative of the coexistence of aligned and randomly oriented fibril domains. For those tracers which are forced along the local director of fibril alignment, the principal direction of anisotropic motion is indicated by a blue line, and we can immediately see that these lines are not aligned over the whole field of view.…”

Section: Resultsmentioning

confidence: 93%

Non-equilibrium nature of two-dimensional isotropic and nematic coexistence in amyloid fibrils at liquid interfaces

et al. 2013

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Two-dimensional alignment of shape-anisotropic colloids is ubiquitous in nature, ranging from interfacial virus assembly to amyloid plaque formation. The principles governing two-dimensional self-assembly have therefore long been studied, both theoretically and experimentally, leading, however, to diverging fundamental interpretations on the nature of the two-dimensional isotropic-nematic phase transition. Here we employ single-molecule atomic force microscopy, cryogenic scanning electron microscopy and passive probe particle tracking to study the adsorption and liquid crystalline ordering of semiflexible b-lactoglobulin fibrils at liquid interfaces. Fibrillar rigidity changes on increasing interfacial density, with a maximum caused by alignment and a subsequent decrease stemming from crowding and domain bending. Coexistence of nematic and isotropic regions is resolved and quantified by a length scale-dependent order parameter S 2D (d). The nematic surface fraction increases with interfacial fibril density, but depends, for a fixed interfacial density, on the initial bulk concentration, ascribing the observed two-dimensional isotropic-nematic coexistence to non-equilibrium phenomena.

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Section: Resultsmentioning

confidence: 93%

Non-equilibrium nature of two-dimensional isotropic and nematic coexistence in amyloid fibrils at liquid interfaces

et al. 2013

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“…94 Relatively large aspect ratios can be found experimentally in the systems of rod-like colloidal suspensions. 11 The focus of our current work is on rod- …”

Section: Equation Of State For Hard Spherocylinders With An Anisotropmentioning

confidence: 99%

“…Since the first discovery of this fascinated state of matter by Reinitzer in the late nineteenth century, 4 LCs have attracted interest because of the uniqueness of their thermodynamic, structural, optical, and electronic properties. Today, one can recognize LC behaviour in an ever increasing number of scenarios: apart from the common examples of solutions of soaps, detergents, and surfactants, 2 the existence of lyotropic liquid-crystalline order in biomacromolecular systems is ubiquitous in nature including the phase behaviour exhibited by DNA, 5,6 by stiff polymers such as polysaccharides, 7 cellulose 8,9 and protein fibers, 10,11 and by rod-like viruses such as the tobacco mosaic virus, 12,13 and the fd virus. [14][15][16][17][18][19] The supramolecular α-helices formed by the self-assembly of polypeptides in solution are also found to give rise to a rich variety of mesogenic behaviour.…”

Section: Introductionmentioning

confidence: 99%

Understanding and Describing the Liquid-Crystalline States of Polypeptide Solutions: A Coarse-Grained Model of PBLG in DMF

Müller

Jackson

2014

Macromolecules

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A perturbation theory is employed to construct a free-energy functional capable of describing the isotropic and nematic phases of attractive rod-like particles. An algebraic van der Waals-Onsager equation of state is then developed to determine the global phase behaviour of prolate particles for various aspect ratios and strengths of the attractive potential. Compared with the phase diagram of their athermal analogues, the incorporation of an attractive potential is seen to stabilize the nematic state leading to an increase in the degree of orientational order of the system at high densities. The most salient feature of these fluids is the existence of regions of nematic-nematic phase separation. The simple model is used to describe the phase behaviour of solutions of a relatively rigid polypeptide, poly-(γ -benzyl-L-glutamate) (PBLG), in dimethylformamide (DMF); this system exhibits a unique phase separation between two liquidcrystalline states. The coarse-grained representation of the mesogen employed herein * To whom correspondence should be addressed 1 is a hard spherocylinder decorated with an attractive square-well potential which acts at the center of mass of the particle. A quantitative description of the experimental isotropic-nematic phase behaviour of the PBLG solutions can be achieved from the proposed model with the use of just two temperature-dependent parameters.

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“…[7][8][9] This link has been strengthened by several observations of native proteins capable of forming amyloid fibrils when their conformation is altered by different thermodynamic or environmental conditions, such as e.g. [11][12][13][14][15][16][17] The physics of intermolecular interaction has been studied for another important type of ordered aggregation, that is crystallization. 10 In this respect, amyloid seems to be a generic structural motif, in which polypeptide chains can organize, and this explains why the molecular bases of amyloid formation are diffusely studied even with model proteins and in nonphysiological conditions.…”

Section: Abstract Protein Stability Amyloid Fibrils Electrostaticsmentioning

confidence: 99%

Thermodynamic versus Conformational Metastability in Fibril-Forming Lysozyme Solutions

2012

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The role of intermolecular interaction in fibril-forming protein solutions and its relation with molecular conformation is a crucial aspect for the control and inhibition of amyloid structures. Here, we study the fibril formation and the protein-protein interactions of lysozyme at acidic pH and low ionic strength. The amyloid formation occurs after a long lag time and is preceded by the formation of oligomers, which seems to be off-pathway with respect to fibrillation. By measuring the osmotic isothermal compressibility and the collective diffusion coefficient of lysozyme in solution, we observe that the monomeric solution is kept in a thermodynamically metastable state by strong electrostatic repulsion, even in denaturing conditions. The measured repulsive interaction between monomers is satisfactorily accounted for by classical polyelectrolyte theory. Further, we observe a slow conformational change involving both secondary and tertiary structure, which drives the proteins toward a more hydrophobic conformation. Denatured proteins are driven out of metastability through conformational substates, which are kinetically populated and experience a lower activation energy for fibril formation. Thus, our results highlight the role of electrostatic repulsion, which hinders the aggregation of partially denatured proteins and operates as a gatekeeper favoring the association of those monomers whose conformation is capable of forming amyloid structure.

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Effects of Charge Double Layer and Colloidal Aggregation on the Isotropic−Nematic Transition of Protein Fibers in Water

Cited by 74 publications

References 26 publications

Non-equilibrium nature of two-dimensional isotropic and nematic coexistence in amyloid fibrils at liquid interfaces

Non-equilibrium nature of two-dimensional isotropic and nematic coexistence in amyloid fibrils at liquid interfaces

Understanding and Describing the Liquid-Crystalline States of Polypeptide Solutions: A Coarse-Grained Model of PBLG in DMF

Thermodynamic versus Conformational Metastability in Fibril-Forming Lysozyme Solutions

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