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ULTRAVIOLET RESONANCE RAMAN STUDY ON PURPLE AND BLUE MEMBRANES OF Halobacterium halobium
Author(s) -
Hashimoto S.,
Miura K.,
Yamagishi T.,
Takeuchi H.,
Harada I.
Publication year - 1992
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.1751-1097.1992.tb09733.x
Subject(s) - chemistry , resonance (particle physics) , amide , excited state , membrane , halobacterium , crystallography , absorbance , raman spectroscopy , solvent , molecule , photochemistry , analytical chemistry (journal) , bacteriorhodopsin , organic chemistry , chromatography , optics , biochemistry , physics , particle physics , nuclear physics
— Two hundred and forty and 213 nm excited resonance Raman spectra of purple membrane (PM) and blue membrane (BM) of Halobacterium halobiurn were studied. Generally intense Trp scattering and a strong relative intensity of the W3 band at 1553 cm ‐1 in the 240 nm spectrum of PM indicate red‐shifted B b absorptions of some Trp sidechains. A high intensity ratio of Trp doublet at 1360 and 1340 cm ‐1 suggests interactions with highly hydrophobic Trp environments. These Trp are not strongly H‐bonded and their N 1 sites are located in positions easily reached by solvent water molecules. Tyrosines are also in very hydrophobic environments and H‐bonded. The mainchain consists of normal and distorted α‐helices whose amide NH are hardly deuterated in D 2 O suspension, and some NH exchangeable irregular segments on the membrane surface. Upon acidification, the ratio of Trp doublet with 240 nm excitation decreases concomitant with increase in retinal absorbance at 600 nm, and the W3 relative intensity and overall Trp scattering also decrease. These observations strongly indicate that the counterpart of Trp interactions in PM is the retinal and that the interactions partly diminish upon acidification. The Tyr environment also changes with the color. Although the 240 nm amide I intensity is greater in acid BM than in PM, the change is not related to the color change because the amide I intensity of deionized BM is practically the same as that of PM. The amide I intensity increase in acid BM is ascribable to a structural change of the surface peptides due to acid induced aggregation.