INTER-LAYER SLIDE AND STRESS RELAXATION IN A BILAYER LIPID MEMBRANE IN THE PATCH-CLAMP SETTING

摘要

In this paper we propose a theory of lateral stress relaxation in a bilayer lipid membrane exposed to external pressure pulse in the patch-clamp experimental setting. It is shown that transfer of lipid molecules into a strained region is thermodynamically advantageous due to local decrease of the stress. Lateral stress relaxation in the monolayer controlling the gating of MscL, bacterial mechanosensiti ve channel of large conductance, triggers thermally activated closure of the open channels ("adaptation"). Considered stress relaxation mechanism may explain the recent experimental observations [Hamill, Martinac, 2001] of adaptation of MscL to sustained membrane stretch. We evaluate the energy barrier separating open and closed states as a function of the tension in bilayer. Allowing for the MscL thermodynamic barrier, we estimate characteristic adaptation times at room temperature to be of the order of seconds, well within the range of the known experimental data. Estimated propagation time of the stretching lateral stress over the micrometer-sized membrane is 4-5 orders of magnitude shorter.