PHOTOMODULATION AND PHOTOPUMPING IN MEMBRANES CONTAINING CARRIERS OPTIMIZED FOR FACILITATED TRANSPORT IN THE DARK

A steady-stale model describing photofacilitated transport in liquid m embranes is presented. The model can be used to consider photoactive c arriers with a wide range of thermodynamic and kinetic properties in o rder to calculate photoinduced transport of solutes down their concent ration gradient (photomodulation) and against their concentration grad ient (photopumping). The description of transport in these systems is generalized by combining the relevant physical constants (diffusion co efficients, rate constants, concentrations, molar absorptivities, ligh t intensity, etc.) into dimensionless parameters. Detailed description s of photomodulation and photopumping are presented for the case where the carrier has properties that are optimal for downhill transport in the dark (thermal transport). Absorption of light by the carrier and carrier solute complex can cause downhill transport to increase by 50% or to decrease by a factor of 4 depending on the light intensity. Pho topumping can be maintained against a 10-fold concentration gradient, The transport efficiencies for photomodulation and photopumping are al so discussed.