Electrostatic properties and stability of charged virus-like nano-shells are examined in ionic solutions with monovalent and multivalent ions. A theoretical model based on a thin charged spherical shell and multivalent ions within the dressed multivalent ion approximation, yielding their distribution across the shell and the corresponding electrostatic (osmotic) pressure acting on the shell, is compared with extensive implicit Monte-Carlo simulations. It is found to be accurate for positive or low negative surface charge densities of the shell and for sufficiently high (low) monovalent (multivalent) salt concentrations. Phase diagrams involving electrostatic pressure exhibit positive and negative values, corresponding to an outward and an inward facing force on the shell, respectively. This provides an explanation for the high sensitivity of viral shell stability and self-assembly of viral capsid shells on the ionic environment.
COBISS.SI-ID: 2605668
We derive the conservation law for nematic polymers in tensorial form valid for quadrupolar orientational order, in contradistinction to the conservation law in the case of polar orientational order. We analyze the differences between the polar and the tensorial forms of the conservation law, present some explicit orientational fields that satisfy the tensorial constraint, and discuss the role of singular hairpins, which do not affect the local quadrupolar order of polymer nematics, but nevertheless influence its gradients.
COBISS.SI-ID: 2615908
We investigate condensation of a long confined chiral nematic polymer inside a spherical enclosure, mimicking condensation of DNA inside a viral capsid. The Landau-de Gennes nematic free-energy Ansatz appropriate for nematic polymers allows us to study the condensation process in detail with different boundary conditions at the enclosing wall that simulate repulsive and attractive polymer-surface interactions. By increasing the chirality, we observe a transformation of the toroidal condensate into a closed surface with an increasing genus, in some respects akin to the ordered domain formation observed in cryo-microscopy of bacteriophages.
COBISS.SI-ID: 2523492
We set up a macroscopic model of bacterial growth and transport based on a dynamic preferred direction - the collective velocity of the bacteria. This collective velocity is subject to the isotropic-nematic transition modeling the density-controlled transformation between immotile and motile bacterial states. The choice of the dynamic preferred direction introduces a distinctive coupling of orientational ordering and transport not encountered otherwise. The approach can also be applied to other systems spontaneously switching between individual (disordered) and collective (ordered) behavior and/or collectively responding to density variations, e.g., bird flocks, fish schools, etc. We observe a characteristic and robust stop-and-go behavior. The inclusion of chirality results in a complex pulsating dynamics.
COBISS.SI-ID: 2620260
We described some aspects of electrostatic interactions in free energy and osmotic pressure of viruses. We found out that DNA and RNA viruses differ in this regard, as the former have a large and pozitive osmotic pressure while the latter have a small and negative osmotic pressure. These differences have important consequences for virus (self)assembly.
COBISS.SI-ID: 25607463