Anisotropic translational diffusion models

A quantitative, albeit indirect, approach to capture the dynamical signature of the coupling between orientational and translational order is to compare the D and D data obtained from our simulations with those predicted by the existing dynamical models, which ignore such coupling. In Fig. 29, we do so by considering two theoretical models [163, 164] that have been applied to trace experimental and molecular dynamics simulation data of anisotropic translational diffusion in the nematic phase of liquid crystalline systems [26-28, 163-165] the Hess-Frenkel-Allen (HFA) model and the Chu and Moroi... 

Rod-like polymers may be represented by rods or rods capped with hemispheres at both ends. In rod-like molecules, anisotropic translational diffusion arising from the airisotropic particle shape is coupled with rotational diffusion to appear in a < i dependence of the initial decay rate of DLS, which has experimentally been observed for the tobacco mosaic vims. °° By finding a proper model, we can characterize the particle shape and size through Rg, Rh, and Rg/Rh, along with P(g) and r(g], which could contain more information. 

In the popular fluid mosaic model for biomembranes, membrane proteins and other membrane-embedded molecules are in a two-dimensional fluid formed by the phospholipids. Such a fluid state allows free motion of constituents within the membrane bilayer and is extremely important for membrane function. The term "membrane fluidity" is a general concept, which refers to the ease of motion for molecules in the highly anisotropic membrane environment. We give a brief description of physical parameters associated with membrane fluidity, such as rotational and translational diffusion rates, order parameters etc., and review physical methods used for their determination. We also show limitations of the fluid mosaic model and discuss recent developments in membrane science that pertain to fluidity, such as evidence for compartmentalization of the biomembrane by the cell cytoskeleton. 

Under this unsuccessful name there is known the simplest and chronologically the first model of chemically anisotropic reaction, formed by translational and rotational motion of partners. It was called so in the original paper /lO/, although applicability conditions formulated by the authors supposed limited number of recontacts, so limited that they might be considered as statistically independent. They exclude a transition to the diffusion limit when the time intervals between successive contacts shorten so that the following contact takes place quite near the previous one. Later the MMDCR appeared to be an exact as3nnptotic method of the encounter theory which holds true when... 

---