Summary

The interactions ofelectrostatic fields with proteins in general, and with biological membranes in particular, are reviewed. Electrostatic fields can modulate protein conformational equilibria, due to differential interactions between the electric field and permanent and induced dipoles, which latter have different values in different protein conformational states. If the relevant con-formational states with different dipole moments are part of an enzyme catalytic ycle, then mod-ulation of the electrical potential will affect he enzyme's catalytic activity (for thermodynamically favourable chemical reactions). If the electrical field is non-stationary, forinstance a sinusoidally modulated field or even "random " electrical noise, enzymes can transduce (or "harvest") free energy from the field for the performance ofchemical or transport work. If two apposed membrane proteins exhibit reversible behaviour of this type (in which conformational transitions coupled to chemical or binding reactions are linked to changes in dipole moments), then energy coupling between chemical reactions catalysed by such proteins is possible, mediated purely via coulombic interactions. Such a model can account for ATP synthesis under conditions in which the time-averaged electrochemical potential difference of protons across an energy-coupling membrane is zero. 1