Ref HAL: hal-01935603_v1
Ref Arxiv: 1501.00258
Ref. & Cit.: NASA ADS
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Résumé:

Changes of external parameters in proximity of critical point can increase thermal fluctuations of tubular lipid membrane (TLM) and result in variation of the membrane shape. The phase transitions in the system are shown to be controlled by a single effective parameter, which depends on the pressure difference between inner and outer regions of membrane and the applied stretching force. We determine an interval of the parameter values corresponding to the stability region of the cylindrical shape of TLM and investigate the behavior of the system in the vicinity of critical instabilities, where the cylindrical shape of membrane becomes unstable with respect to thermal fluctuations. The applied boundary conditions strongly influence the behavior of TLM. For example, small negative effective parameter corresponds to chiral shape of TLM only in the case of periodic boundary conditions. We also discuss other three types of phase transitions emerging in the system.

Commentaires: 15 pages, 6 figures, in Russian

Résumé:

Theory of crystallization and structure of small virus capsids and ribonucleoprotein nanoparticles

Ref HAL: hal-01236224_v1
DOI: 10.1140/epje/i2015-15112-6
WoS: WOS:000363957800001
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5 Citations
Résumé:

Tubular lipid membranes (TLMs) are formed by an external pulling force from artificial or biological bilayer vesicles and can be subsequently stabilized by incorporating proteins or amphiphilic polymers into the lipid bilayer. The arising spontaneous curvature of the lipid sheet allows switching off the pulling force without TLM destabilization. However, here we show that during this process two different thermal fluctuation modes drastically increase their amplitudes making fluctuations of the TLM much greater than its radius. Due to the system’s proximity to the critical fluctuation point, a weak axial compressive force is sufficient to destabilize the TLM. Its absolute value is shown to be much smaller than that of the pulling force required for the initial lipid nanotube formation. Induced complex instability was studied in the frame of Landau phase transition theory. The process involves two consecutive second-order phase transitions and leads to the tube deformation combining annular corrugation with completely unconventional chiral buckling.

Résumé:

STRUCTURE OF VIRAL CAPSIDS AND LANDAU CRYSTALLIZATION THEORY

Ref HAL: hal-01208532_v1
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Résumé:

Viruses are organized biological nanosystems which display high levelof spatial organization. In the present work we focus on the group theory methods application to the problems of virus self-assembly and resulting viral structure formation. The approach is based on the successive application of methods of representation theory for continuous and discrete groups and invariant theory for the groups not-generated by reflections. It generalizes the Landau density wave theory of crystallization to the case of compact crystal-like manifold assembly. To compare the predictions of the theory with the available cryoelectronic microscopy data we use the calculated density distribution functions which generate the protein positions on a spherical surface of the cage protecting viral genome. We also discuss therelation between density distribution functions and viral infectivity.

Résumé:

Formation of dodecagonal quasicrystalline structures on spherical substrates

Résumé:

Structure-Assembly Relations in Viruses: From Density Waves to Spherical Crystallography