Chlorophyll RC I, its Structure, Function and Biosynthesis

Abstract

In all photosynthetic organisms the bulk of pigments is designated to collect light energy and to funnel this energy to reaction centers, in which the primary charge separation takes place. Compared to the mass of antenna pigments, the chromophores capable for charge separation in the reaction centers amount only to about 0.5% or less. Whereas the antenna pigments of organisms with oxygenic photosynthesis are well characterized as chlorophylls a and b, phycobilins and in some cases carotenoids, little is known about the nature, arrangement and action of their reaction center pigments. First knowledge about the nature of the reaction center chromophore(s) of photosystem I (PS 1) derived from the detection of the long wavelength absorbing pigment P-700 by Bessel Kok (1). P-700 can be determined by its absorption changes connected with its redox changes in vivo and its concentration can be calculated following Ke et al. (2). It was generally assumed that P-700 is a di-or monomeric form of chlorophyll a, attached to the proteins of the thylakoids in a different way compared to antenna chlorophylls.