The general aim of this project is to study the molecular mechanisms of free energy transduction in biology, such as in muscle contraction, active transport, flagellar rotation, etc. During this period, our work was concentrated on the continuing studies of fluctuation-induced active transports of ligands across membranes. It was suggested theoretically a few years ago that randomly fluctuating electric fields could be absorbed by charged ligand transporters and used to pump ligands across a membrane against a concentration gradient. In collaboration with Tsong and his colleagues we showed in this work that this prediction indeed could be verified experimentally using random telegraphy-type fluctuations. To provide a molecular description of the system, we developed a simple four-state transport model capable of simulating the measured data. We also investigated theoretically the general dynamic properties of a simplified two-state transport system under the influence of alternating rectangular (regularly oscillating) electric pulses, in relation to the general questions of how the fluctuating electric field and the ligand transport systems are coupled.
