title: Jump rates for anisotropic particles. Model calculations for the transport of water molecules through membrane channels.
abstract: A theoretical analysis for site-to-site jump rates for anisotropic molecules is presented. The molecular shape is regarded as a mechanical anisotropy in the form of finite moments of inertia, as well as anisotropy with respect to the interaction potential. The mutual coupling between rotational and translational motion necessarily produces a competitive effect between the equilibrium alignment in the local field and the precession of the figure axis, leading to an increase of the effective activation energy. As a numerical example the jump rate for a water molecule in a gramicidin-like channel has been calculated, and a temperature-independent reduction of some 15% for the rate as compared to the point-like molecule has been found.
mesh_terms: D001692:Biological Transport; D055592:Biophysical Phenomena; D001703:Biophysics; D006096:Gramicidin; D007473:Ion Channels / Q000378:metabolism*; D007700:Kinetics; D013816:Thermodynamics; D014867:Water / Q000378:metabolism*
chemical_list: D007473:Ion Channels; D014867:Water; D006096:Gramicidin