Open AccessInvestigation of the Primary Photochemistry of Bacteriorhodopsin by Low‐Temperature Fourier‐Transform Infrared Spectroscopy
Author(s) -
SIEBERT Friedrich,
MÄNTELE Werner
Publication year - 1983
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1983.tb07187.x
Subject(s) - bacteriorhodopsin , schiff base , chemistry , protonation , fourier transform infrared spectroscopy , retinal , photochemistry , infrared spectroscopy , spectroscopy , infrared , crystallography , organic chemistry , optics , physics , membrane , biochemistry , ion , quantum mechanics
The method of Fourrier‐transform infrared difference spectroscopy was applied to investigate the transition at 77K of bacteriorhodopsin in its light‐adapted form to K 610 , the first intermediate which is stable at low temperature. In addition to unmodified bacteriorhodopsin, bacteriorhodopsin in 2 H 2 O and bacteriorhodopsin containing [15‐ 2 H]retinal was used. The results show that major rearrangements occur in the Schiff base in this transition. It is not possible to identify a C=N stretching vibration of the Schiff base in K 610 . The identification of an N‐H bending vibration in K 610 shows that the nitrogen of the previous Schiff base still has a proton attached. The fingerprint region exhibits very unusual features for K 610 and bears no similarity to protonated retinylidene Schiff base model compounds of any isomeric composition. Therefore, no conclusions on the isomeric state of the retinal in K 610 can be drawn. The spectra show that the terminal part of the retinal is predominantly reflected in the difference spectra. This indicates that the most polar part of the retinal is located near the Schiff base. We have evidence for protein molecular changes occurring in this transition at 77K.