Spectroscopy and photochemistry of retinals. I. Theoretical and experimental considerations of absorption spectra

Becker, Ralph S.; Inuzuka, Kōzō; Balke, David E.

doi:10.1021/ja00730a006

Cited by 40 publications

(21 citation statements)

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Section: Absorption Spectramentioning

confidence: 59%

“…From Zechmeister's work (9) it is clear that in carotenes the 1 A: state (the cis peak) is intermediate in energy between the two 1 Bu states. Theoretical calculations reproduce this energy ordering for these three states (13,44,52,53).The position of the remaining 1 A; state has been somewhat problematical. Standard PPP calculations (13, 53) indicate that it too should lie between the two 1 Bu states although whether it is higher or lower in energy than the cis peak depends on the parameters used in these calculations (54).…”

mentioning

confidence: 78%

“…The spectra of retinal isomers have been extensively studied both in solutions and in rigid glasses at 77°K (42,53,60,61). Three bands are evident for all isomers, an intense band at about 370-380 nm and two weaker bands centered at 280 and 250 nm.…”

Section: Spectra Of Retinal Isomersmentioning

confidence: 99%

“…Standard PPP calculations (13,53) indicate that it too should lie between the two 1 Bu states although whether it is higher or lower in energy than the cis peak depends on the parameters used in these calculations (54). However, recent low-temperature and radiative-lifetime studies by Christensen, Hudson & Kohler (55-58) have detected in polyenes a weak transition whose energy is lower than the main 1 Hu state.…”

Section: Absorption Spectramentioning

confidence: 99%

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The Structure and Spectra of the Chromophore of the Visual Pigments

Honig¹,

Ebrey²

1974

Annu. Rev. Biophys. Bioeng.

139

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Visual pigments consist of a chromophore, II-cis retinal (Figure ld) (or 3-dehydroretinal) covalently bound to a protein called an opsin. The pigments are situated in specialized membranes in vertebrate and invertebrate photoreceptors; the best studied, rhodopsin, is found in vertebrate rod outer segments. Light absorption by the visual pigments initiates a series of events that leads to the excitation of the photoreceptor cell. The mechanism of visual excitation is for the most part poorly understood although considerable progress has been made in understanding the structure and control of permeability of photoreceptor membranes (1, 2). The primary process in visual excitation elucidated by Wald, Hubbard and their colleagues (3) appears to be the photochemical isomerization of the chromophore to its all-trans conformation (Figure la). How this molecular event triggers the sequence of steps involved in visual excitation is unknown. To explain this will require understanding the properties of the isolated chromophore and its interactions with opsin as well as the structure of the pigment and the disk membrane in which it is located.This review is concerned with the conformational and spectroscopic properties of the chromophore, both when isolated in solution and when bound to an opsin to form a pigment. Due in part to advances in the underlying theory that have been stimulated by interest in the visual chromophore, the physical and theoretical chemistry of retinal isomers is now fairly well understood. The nature of the chromophore in the pigment is still uncertain although a number of recent experimental and theoretical studies have provided considerable insigh t as to possible modes of interaction.This article divides naturally into two parts. In the first section we discuss the ground and excited-state properties of the isolated retinal molecule; in the second we review the spectroscopic properties of the visual pigments and various theoretical models that have been proposed to explain the chromophore-opsin interaction. We 151 :-:9037 Annu. Rev. Biophys. Bioeng. 1974.3:151-177. Downloaded from www.annualreviews.org Access provided by New York University -Bobst Library on 07/24/15. For personal use only. Quick links to online content Further ANNUAL REVIEWS 152 HONIG & EBREY (a) (b) CH3 (e) (d) 0 (e) 0 (tl 0 016 (g) Figure I Conformations of retinal: (a) 6 s-cis, all-trans, (b) 6 s-trans, all-trans, (c) 6 s-cis,9-cis, (d) 12 s-trans, 11-cis, (e) 12 s-cis, ll-cis, (I) 12 s-trans, ll-cis, 14-methyl, (g) 12 s-cis, ll-trans; ¢6-7, ¢,0-1 1 ' ¢ 1 l-12 , and ¢,2-13 are the dihedral angles about bonds 6C-7C, lOC-llC, llC-12C, and l2C-13C respectively; 3,4 dehydroretinai has an extra double bond in the ring between 3C and 4C are concerned primarily with the chromophore and our discussion of the visual pigment is limited to phenomena in which we believe it is directly involved. A number of earlier reviews and collections of articles on visual pigments provide useful back ground material and cover many important topics not ...

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Section: Absorption Spectramentioning

confidence: 59%

mentioning

confidence: 78%

Section: Spectra Of Retinal Isomersmentioning

confidence: 99%

Section: Absorption Spectramentioning

confidence: 99%

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The Structure and Spectra of the Chromophore of the Visual Pigments

Honig¹,

Ebrey²

1974

Annu. Rev. Biophys. Bioeng.

139

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“…There has been a question as to which of these absorption bands is the ci8 peak (4)(5)(6)(7)(8). We discuss the assignments of these transitions in a subsequent publication (Honig, B., Kliger, D., Ebrey, T. & Karplus, M., in preparation).…”

mentioning

confidence: 95%

Ultraviolet Chromophore Transitions in the Rhodopsin Spectrum

Ebrey¹,

Honig²

1972

Proc. Natl. Acad. Sci. U.S.A.

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Difference spectra measured at -105°s how two decreases in the ultraviolet absorption spectrum of rhodopsin upon bleaching that cannot be attributed to changes in protein conformation. These absorbancy decreases in rhodopsin are consistent with a cis-trans isomerization of the chromophore.Rhodopsin, the visual pigment, consists of the chromophore 11-ci retinal covalently bound to the protein opsin (1). As seen in Fig. 1, the two principal peaks in the absorption spectrum of rhodopsin are located at 280 and 500 nm. The short-wavelength absorption is due primarily to the aromatic amino acids of opsin; the band at 500 nm corresponds to the lowest r-xr* transition of the chromophore shifted by the protein from 380 nm to the visible region of the spectrum. In addition to the two major bands, there is a weaker peak at 340 nm that is most easily seen in pure preparations of rhodopsin. This band has often been termed the rhodopsin "cis" peak, since it is believed to correspond to the cis peak of the isomers of retinal (2).Retinal isomers have two subsidiary peaks in the ultraviolet, one at 250 and the other at 280 nm (3). There has been a question as to which of these absorption bands is the ci8 peak (4-8). We discuss the assignments of these transitions in a subsequent publication (Honig, B., Kliger, D., Ebrey, T. & Karplus, M., in preparation). In this work, we are concerned only with the identification of two corresponding transitions in the spectrum of rhodopsin. Our approach is to measure changes in the ultraviolet spectrum of rhodopsin that result entirely from the isomerization of the chromophore.Our spectroscopic results enable us to identify early stages in the bleaching sequence of rhodopsin, in which the protein has not undergone measurable conformational changes. Furthermore, they provide another test for Hubbard and Wald's (9) finding that the chromophore of rhodopsin is directly isomerized by light, and that changes in the protein take place at a later time. Finally, they provide a more complete description of the spectroscopic changes that result from the formation of rhodopsin from 11-ci.s retinal and opsin. METHODS AND MATERIALSAll low-temperature spectra presented here were measured with rhodopsin from outer segments of bovine rods, which were prepared by the methods of Ebrey (10), hardened in 4% aluminum potassium sulfate, and solubilized in 2% digitonin.Rhodopsin prepared with digitonin as a detergent is not as free from protein contaminants as rhodopsin that has been solubilized with other detergents, such as Ammonyx LO, and then has been purified by calcium phosphate chro-1897 matography (10). However, since we are only interested in difference spectra, absolute shapes of absorption spectra are not necessary.All of the difference spectra reported here were measured at -105°; other measurements at -80°gave essentially identical results. It is necessary to determine difference spectra at low temperatures for two reasons, (a) at room temperature (240), two of the bleaching products of the rhod...

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