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NEAR‐INFRARED‐FT‐RAMAN STUDY OF AGGREGATION OF BACTERIOCHLOROPHYLL c IN WHOLE LIVING Chlorobium limicola
Author(s) -
Sato Hidetoshi,
Uehara Kaku,
Ishii Takasada,
Ozaki Yukihiro
Publication year - 1995
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1995.tb02376.x
Subject(s) - chlorosome , bacteriochlorophyll , chemistry , raman spectroscopy , photochemistry , dimer , crystallography , organic chemistry , pigment , physics , optics
— Near‐infrared excited Fourier‐transform Raman spectra have been measured for whole living Chlorobium limicola f. thiosulfatophilum to explore in situ structure of bacteriochlorophyll c (BChl‐ c ). The spectra, whose Raman bands are preresonance enhanced via a Qy band of BChl‐ c , did not contain contributions from the major components of bacteria such as proteins and lipids. Therefore, the spectra provide selective structural information about BChl‐ c in the chlorosomes in a totally nondestructive manner. A marker band, appearing at 1605 cm‐1 for the coordination number of the Mg atom, shows that BChl‐ c in the chlorosomes is five coordinate. The Raman spectrum of living bacteria closely resembles that of BChl‐c in water‐saturated carbon tetrachloride (w‐std CC14) where it is comprised of dimer, tetramer and polymer spectra. However, a band assigned to a C=O stretching mode of the 131‐keto group is identified only at 1641 cm‐1. A band arising from the free keto carbonyl group, which appears in the spectrum of BChl‐c in w‐std CC14, is not observed in the spectra of bacteria. These observations suggest that BChl‐ c in the chlorosomes forms mostly coordinate polymeric species whose structure is very similar to that of BChl‐ c in w‐std CC14.