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NEW SPECTRAL COMPONENTS IN HIGH RESOLUTION ABSORPTION SPECTRA OF GREEN BACTERIAL REACTION CENTER COMPLEXES AT 5K *
Author(s) -
Whitten William B.,
Pearlestein Robert M.,
Olson John M.
Publication year - 1979
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.1751-1097.1979.tb07772.x
Subject(s) - bathochromic shift , absorbance , bacteriochlorophyll , chemistry , photochemistry , trimer , absorption (acoustics) , absorption spectroscopy , spectral line , wavelength , visible spectrum , dithionite , delocalized electron , analytical chemistry (journal) , crystallography , dimer , materials science , fluorescence , optics , chromatography , organic chemistry , physics , astronomy , pigment , enzyme , optoelectronics , composite material
—absorption spcctra of reaction center Complexes I and II from Chlorobium limicola f. thiosul‐fatophilum were taken from 760 and 860 nm at 5 K. Fourth and eighth derivatives of the spectra were calculated from the digital data. Light‐minus‐dark difference spectra were taken, also at 5 K, with 590 nm actinic light. A shoulder not visible at 77 K appears on the long wavelength side of the 834 nm peak in Complex I. In Complex II, which is derived by guanidine HCI treatment of I, the shoulder is much more pronounced; derivative peaks appear at 834 and 838 nm. In the difference spectra, there are troughs at 832 and 838 nm. The latter trough is the first instance in green bacteria of a wavelength coincidence between a light‐induced bleaching and a peak in (derivative) absorbance. There is also a nearly symmetrical pair of features, a trough at 814 nm and a peak at 818 nm, that appear to represent a light‐induced bathochromic shift of the absorbance at 816 nm, a peak which occurs in both complexes as well as the photochemically inert bacteriochlorophyll a (Bchl a ) protein. Other features in the absorption spcctra of both Complexes occur at virtually the same wavelengths as the peaks in purified Bchl a ‐protein trimer. We conclude that a large fraction of the Bchl a in Complex II is in a conformation similar to that of a single subunit of Bchl a ‐protein.