Ref HAL: hal-00802240_v1
PMID 23260049
DOI: 10.1016/j.bpj.2012.11.008
WoS: 000312527500009
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17 Citations
Résumé:

Precisely how malaria parasites exit from infected red blood cells to further spread the disease remains poorly understood. It has been shown recently, however, that these parasites exploit the elasticity of the cell membrane to enable their egress. Based on this work, showing that parasites modify the membrane's spontaneous curvature, initiating pore opening and outward membrane curling, we develop a model of the dynamics of the red blood cell membrane leading to complete parasite egress. As a result of the three-dimensional, axisymmetric nature of the problem, we find that the membrane dynamics involve two modes of elastic-energy release: 1), at short times after pore opening, the free edge of the membrane curls into a toroidal rim attached to a membrane cap of roughly fixed radius; and 2), at longer times, the rim radius is fixed, and lipids in the cap flow into the rim. We compare our model with the experimental data of Abkarian and co-workers and obtain an estimate of the induced spontaneous curvature and the membrane viscosity, which control the timescale of parasite release. Finally, eversion of the membrane cap, which liberates the remaining parasites, is driven by the spontaneous curvature and is found to be associated with a breaking of the axisymmetry of the membrane.

Ref HAL: hal-00663020_v1
DOI: 10.1103/PhysRevLett.108.038102
WoS: 000299329100030
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16 Citations
Résumé:

On the example of exceptional families of viruses we (i) show the existence of a completely new type of matter organization in nanoparticles, in which the regions with a chiral pentagonal quasicrystalline order of protein positions are arranged in a structure commensurate with the spherical topology and dodecahedral geometry, (ii) generalize the classical theory of quasicrystals (QCs) to explain this organization, and (iii) establish the relation between local chiral QC order and nonzero curvature of the dodecahedral capsid faces.

Ref HAL: hal-00654054_v1
Ref Arxiv: 1105.3337
Ref. & Cit.: NASA ADS
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Résumé:

Understanding of virus capsid organization and self-assembly mechanisms helps to get an insight into the protein interactions which render virus infectious, but also to advance new methods in nanotechnology which use capsid self-assembly to produce virus-like nanoparticles. As in abiotic nanostructures, the obstacles along this way are related not only to the nanoscopic size of capsids but also to their unconventional topology and symmetry. In the present work on the example of exceptional families of viruses we : i) show the existence of a completely new type of organization, resulting in a chiral pentagonal quasicrystalline order of protein positions in a capsid with spherical topology and dodecahedral geometry; ii) generalize the classical theory of quasicrystals (QC) to explain this organization and demonstrate that a particular non-linear phason strain induces chirality in QC; and iii) establish the relation between chiral order and inhomogeneous buckling strain of the capsid shell.

Commentaires: 8 pages, 2 figures

Ref HAL: hal-00653999_v1
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Résumé:

Tubular lipid membranes (TLMs) are nanoscopic cylindrical assemblies that play a fundamental role in many intracellular and intercellular processes like protein trafficking, signaling and organelle morphogenesis. TLMs are generated by different mechanochemical actions, ranging from mechanical forces produced by motor proteins pulling at one TLM-end up to specific chemical activities of membrane-associated proteins. We develop here a theory of a resonant effect in protein-membrane coupling taking place in the vicinity of instabilities in tubular lipid membranes (TLMs) under longitudinal force and pressure difference constraints. Two critical low-energy modes defining the stability domain boundaries are found. We show that these modes mediate long-range TLM-protein coupling and interactions between absorbed proteins. Besides, TLM mechanical instabilities strongly influence protein desorption and protein cluster nucleation on TLMs. Experiments involving nanomechanical devices extracting TLM over a large spectrum of mechanochemical conditions can directly test model predictions.

Ref HAL: hal-00654001_v1
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Résumé:

Viruses are biological systems with high level of spatial organization well suited to modern physical methods of study. Viral genome is protected by a solid protein shell (capsid) made of many copies of identical subunits. Recent physical and biochemical data rise a whole number of questions concerning unconventional positional order of subunits in the shell, thermodynamics and physical mechanisms of the self-assembly, shape and mechanical stability of the shell. In the present work we develop the theory which explains and classifies the capsid structures for viruses with spherical topology and icosahedral symmetry. We develop an explicit method which predicts the positions of centers of mass for the proteins, including the capsids of unusual viruses discovered quite recently, and discuss the assembly thermodynamics. We show the relation between the protein density distributions obtained and the infectivity properties for several human viruses. To illustrate the notions of the theory and the results obtained we focus on viruses of the Flavivirus family, their herringbone-like structure, infectivity and pH-driven capsid reconstruction during the maturation process in the cellular pathway. Universal characteristics of polymorphic mutant viruses are introduced.

Ref HAL: hal-00608679_v1
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Ref HAL: hal-00654104_v1
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Résumé:

In the present work we generalize Landau theory of crystallization to explain and to classify the capsid structures of small viruses with spherical topology and icosahedral symmetry. We develop an explicit method which predicts the positions of centers of mass for the proteins constituting viral capsid shell. The peculiarities of the assembly thermodynamics are also discussed. Finally, we show the relation between the protein density distributions obtained and the infectivity properties of several human viruses.