Derivative Absorption Spectroscopy of the Pigment-Protein Complexes from Rhodopseudomonas capsulata

The near infrared absorption spectra and their fourth derivative were measured in membrane preparations or in the isolated light harvesting pigment-protein complex B 800-850 from Rhodopseudomonas capsulata in order to know how the underlying molecular absorption spectra contribute to the observed absorption curve. In contrast to the observations of Cogdell and Crofts [Biochim. Biophys. Acta 502, 409 (1978)] no splitting of the 855 nm absorption bands was observed at 300 K, 100 K, and 4 K. However, a small but significant splitting of the 870 nm band in all derivates (2nd, 4th, 6th) was observed at 300 K and 4 K. The lack of splitting of the 855 nm absorption band will be discussed in the light of the molecular organization of the B 855 moiety of this light harvesting bacteriochlorophyll-protein complex.