The kinetics of cone visual pigments in man

Abstract

Rushton's general kinetic equation for human cone pigments is tested by estimating the photolysis rate at equilibrium from the initial photolysis rate and comparing it to the equilibrium rate of regeneration measured immediately after the bleaching light is turned off. Thirty-seven experiments carried out at a variety of intermediate bleaches confirm the validity of this equation. The hypothesis that the regeneration rate depends upon the store of 11-cis retinal leads to the expectation that recovery from a prolonged weak bleach will proceed with a shorter time constant than recovery from a long intense bleach, and this is not found. This could happen if even the prolonged weak bleach depleted the 11-cis store but this possibility is excluded by an experiment in which recovery is measured following 5 sec full bleaching which follows straight on a prolonged weak one. Why recovery from short full bleaches proceed twice as fast as recovery from long full ones remains unexplained.