Self-regulation phenomena applied to bacterial reaction centers: 2. Nonequilibrium adiabatic potential: dark and light conformations revisited.

Experimental and theoretical results in support of nonlinear dynamic behavior of photosynthetic reaction centers under light-activated conditions are presented. Different conditions of light adaptation allow for preparation of reaction centers in either of two different conformational states. These states were detected both by short actinic flashes and by the switching of the actinic illumination level between different stationary state values.