Characterization of Field-induced Dynamical States and Equilibrium Phases of Charged DNA-viruses: In-situ Electric field Small Angle Dynamic Light Scattering and Image-time Correlation.

The phase behavior of fd-viruses (a filamentous DNA-virus) is strongly affected by ionic strength. In equilibrium, the ionic strength determines the effective thickness and the degree of electrostatic screening of the chirality of their core, and therefore affects the concentration where phase transitions occur and the type of phases that are observed. At sufficiently low ionic strengths, nematic and chiral-nematic (meso) phases, a glass state, and several types of orientaional textures are found. Due to the very high bare charge density of the viruses, there is a large amount of condensed ions, that is, ions that are located in the immediate vicinity of the core of the viruses. Under the influence of a low AC external electric field, these condensed ions dissociate/associate, and give rise to new phases that are not found in equilibrium. In particular, a dynamical state is observed, where nematic-domains persistently melt and reform, and a critical point exists in the divergence of time and the domain size, below a critical ionic strength of about 1.2 mM. In this talk, I first discuss the slow dynamics of chiral-mesophases and the glass in equilibrium and the phase transitions in electric fields, with an emphasis on the so-called image-time correlation technique and dynamic light scattering to quantify the kinetic behaviors of field-induced dynamical states. Secondly, a short overview will be given on the response of concentrated suspensions of charged DNA rods to shear flow. Here, various types of inhomogeneous flow patterns are observed, depending on both the concentration and shear rate. If time allows, I will also present some preliminary results on the interpenetration of negatively charged fd-virus-viruses into the “membrane” of positively charged Giant Unilamellar Vesicles (GUVs), and on protein (lysozyme) aggregation, in the presence of an electric field