ESTIMATION OF PIGMENT STOICHIOMETRIES IN PHOTOSYNTHETIC SYSTEMS OF PURPLE BACTERIA - SPECIAL REFERENCE TO THE (ABSENCE OF) 2ND-CAROTENOID IN LH2

In this short communication we present the stoichiometric ratio of bac teriochlorophyll, bacteriopheophytin and carotenoids in a few photosyn thetic purple bacteria complexes (whose two-dimensional or three-dimen sional structures are well known) determined using the spectrum-recons truction method (SRCM), An important conclusion of our pigment stoichi ometric analysis is the evidence for the absence of the second caroten oid in the light-harvesting complex 2 (LH2). In the process, we also h ighlight the useful application of SRCM in determining the molar extin ction coefficients of carotenoids present in LH1, LH2 or reaction cent ers for which these values are not known due to isolation problems and /or stability.