Transitory pigment-protein complexes similar to photosynthesis active centres during protochlorophyll(ide) photoreduction

By illuminating etiolated bean leaves (Phaseolus vulgaris, var. Commodore) at temperatures around 178 K, and by freezing them in liquid nitrogen, hitherto unknown intermediates in the reduction of protochlorophyll(ide) to chlorophyll(ide) have been trapped. These intermediates appear to have red absorption bands located at wavelengths longer than 680 nm, up to 750 nm. They consist of pigment-protein complexes with a very short life time at room temperature. They do not emit any appreciable fluorescence at 77 K. When heated to temperatures above 178 K, they are transformed in the dark into a chlorophyll(ide)-protein complex: the P688-678 form already described. Energy is transferred from short wavelength absorbing pigments to the intermediate long wavelength pigments. The significance of the intermediates described, especially their similarity to photosynthetic reaction centres, are discussed briefly. © 1977.