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Dark-adapted bacteriorhodopsin contains 13-cis, 15-syn and all-trans, 15-anti retinal Schiff bases

Journal Article · · Proc. Natl. Acad. Sci. U.S.A.; (United States)
; ; ; ; ; ; ;

/sup 13/C NMR spectra of lyophilized dark-adapted (14-/sup 13/C)retinyl-labeled bacteriorhodopsin show a large anomalous upfield shift for the /sup 13/C-14 resonance assigned to the 13-cis isomer, relative to both the all-trans isomer and model compounds. We attribute this to the so-called ..gamma.. effect, which results from a steric interaction between the C-14 retinal proton and the protons on thesuch that CH/sub 2/ of the lysine. As a consequence of this observation, we infer that dark-adapted bacteriorhodopsin is composed of a mixture of all-trans, 15-anti (trans or E) and 13-cis, 15-syn (cis or Z) isomers. These occur in an approximate 4:6 ratio and are commonly identified as bR/sub 568/ and bR/sub 548/. This conclusion is based on an examination of the isotropic chemical shifts and a comparison with /sup 13/C shifts of the carbons adjacent to the C=N linkage in protonated ketimines. Other possible origins for the anomalous shift are examined and shown to be insufficient to account for either the size of the shift or the nature of the shift tensor. We discuss the consequences of this finding for the structure and photochemistry of bacteriorhodopsin. 32 references, 2 figures, 3 tables.

Research Organization:
Harvard Medical School, Boston, MA
OSTI ID:
6029112
Journal Information:
Proc. Natl. Acad. Sci. U.S.A.; (United States), Journal Name: Proc. Natl. Acad. Sci. U.S.A.; (United States) Vol. 81:6; ISSN PNASA
Country of Publication:
United States
Language:
English

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Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
AMINO ACIDS
BARYONS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOLOGICAL ADAPTATION
CARBON 13
CARBON 14
CARBON ISOTOPES
CARBOXYLIC ACIDS
CHEMICAL COMPOSITION
CHEMICAL SHIFT
ELECTROMAGNETIC RADIATION
ELEMENTARY PARTICLES
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
FERMIONS
HADRONS
IMINES
ISOTOPE APPLICATIONS
ISOTOPES
LABELLED COMPOUNDS
LIGHT NUCLEI
LYSINE
MAGNETIC RESONANCE
MOLECULAR STRUCTURE
NUCLEAR MAGNETIC RESONANCE
NUCLEI
NUCLEONS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PIGMENTS
PROTEINS
PROTONS
RADIATIONS
RADIOISOTOPES
RESONANCE
RHODOPSIN
SCHIFF BASES
STABLE ISOTOPES
TRACER TECHNIQUES
VISIBLE RADIATION
YEARS LIVING RADIOISOTOPES