Origins of inhomogeneous broadening in the vibronic spectra of visual chromophores and visual pigments

Birge, Robert R.; Bocian, David F.; Hubbard, Lynn M.

doi:10.1021/ja00369a008

Cited by 65 publications

(57 citation statements)

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“…It is to be expected that the conformation around the C&Z7 single bond in 5-demethylretinal is much more planar than in retinal itself (-60") [14,15] due to the absence of the steric hindrance between the 5-CH3 and the 8-H. This is in agreement with the suggestion [5,16] that upon binding of retinal to b0 the protein forces the chromophore to adopt a more planar ring-chain conformation than in free retinal.…”

Section: Discussionsupporting

confidence: 78%

(5‐demethyl)‐Bacteriorhodopsin analogue: its formation and light‐driven proton pump action

et al. 1983

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The binding of the isomers fall-trans, tfcis, f f-c& and 94s) of ~~~~~t~~lr~t~~~ to ~~~t~~i~o~~~~ and the light-dark adaptation as well as the tight-driven proton pump action of the resulting bacteriorhodopsin analogue were studied. The (Sdemethyl)-bacteriorhodopsin is formed -3-times faster than unmodified bacteriorhodopsin and shows an efficient light-driven proton pump action. These findings show that upon binding of retinal to bacterioopsin the protein forces the chromophore to adopt a more planar ring-chain conformation than in free retinal.~~obacterium hatobium &r@e mernb~~e Proton pumpChromoproteins with a retinylidene chromophore such as bacteriorhodapsin, visual pigments and retinochrome, play an important role in photobiology [I]. Bacteriorhodopsin (hereafter bR), the light energy converting protein of the purple membrane of the halo~hili~ microorganism Iiutobucreriwn halobium, occurs in a light-(Amax = 570 nm) and in a dark-adapted form (hmBX = 560 nm) [2]* The chromophore of the lightadapted form is an all-irons retinylidene moiety. In the dark-adapted form a 1: 1 ~~~ibrium between 13-t& and all-Pans isomers exists [Z].retinal does not bind to bO [Ltf* In continuation of our study on the effect of the different methy groups in retinal upon the binding properties and the light-driven proton pump action of bR [7], we now report on the binding properties of 5-demethyiretinai ( fig. 1) (in its dl-trans, 13-c&, 1 I-& and 9-c& form) to bO. The light-dark adaptation together with the light-driven proton pump action of (%demethyl)-bR are also discussed. 2, MATERIALS AND METHODS The

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Section: Discussionsupporting

confidence: 78%

(5‐demethyl)‐Bacteriorhodopsin analogue: its formation and light‐driven proton pump action

et al. 1983

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“…[1][2][3][4] The absorption spectra of retinals are characterized by three bands. 1,9 The principal absorption band, which is broad and diffuse, even when recorded in a low-temperature matrix, has a maximum around 3.3 eV ͑in hexane at room temperature͒. The two additional transitions at Ϸ4.4 and Ϸ5 eV are weaker.…”

Section: Introductionmentioning

confidence: 99%

Ab initiostudy on the low-lying excited states of retinal

Merchán

González‐Luque

1997

The Journal of Chemical Physics

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Ab initio results for the electronic spectrum of all-trans-retinal and its truncated model 3-methyl-all-trans (10-s-cis)-2,4,6,8,10-undecapentaen-1-al are presented. The study includes geometry determination of the ground state. Vertical excitation energies have been computed using multiconfigurational second-order perturbation theory through the CASPT2 formalism. The lowest singlet excited state in gas phase is predicted to be of nπ* character. The lowest triplet state corresponds, however, to a ππ* state. The most intense feature of the spectrum is due to the strongly dipole-allowed ππ* transition, in accordance with the observed maximum in the one-photon spectra. The vertical excitation energies of the Bu- and Ag-like states are found close, the latter ≈1 eV higher than the maximum in the two-photon spectra. Solvent effects and nonvertical nature of the observed maximum in the two-photon spectra are invoked in rationalizing the deviation with respect to the best present estimate for the Ag-like state. In addition, qualitative aspects of the one-bond photoisomerization about the C11=C12 double bond of retinal are considered. The overall isomerization picture from 11-cis into all-trans-retinal, as taking place mainly along the triplet manifold, agrees with experimental evidence.

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“…Thus, the majority of experimental studies have utilized electronic absorption (6)(7)(8)(9)(10), resonance Raman (11,12), nuclear magnetic resonance (13), Fourier-transform IR (14)(15)(16), or picosecond spectroscopy (17,18). The above-cited experimental, as well as theoretical (19)(20)(21)(22)(23)(24), investigations are not in general agreement concerning the state of protonation of the chromophore (see, for example, refs. 2, 3, 5-8, 11-16, and 18-24) or the number and location of the counterions inside the binding site (2, 6-8, 18-21, 23).…”

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Two-photon spectroscopy of locked-11-cis-rhodopsin: evidence for a protonated Schiff base in a neutral protein binding site.

Birge¹,

Murray²,

Pierce³

et al. 1985

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

133

102

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We studied the nature of the protein binding site of rhodopsin, using two-photon spectroscopy to assign the location of the low-lying "covalent" A *.-like 1rir* state in a model rhodopsin containing a locked-li-cis chromophore. The two-photon thermal lens maximum is observed at 22,800 cm-, "2000 cmt above the one-photon absorption maximum, is also proposed. The latter model is interesting because it also accommodates the observed deuterium isotope effect in the form of a proton translocation between the two residues. The translocation is assumed to be a ground state process, initiated subsequent to the photoisomerization of the chromophore and energetically driven via destabilization of the counterion environment as a result of isomerization-induced charge separation.The nature of the protein binding site of rhodopsin is a subject of intense study (1-18) and continued debate (for recent reviews see refs. [1][2][3][4][5]. Despite the efforts of many researchers, well-ordered three-dimensional crystals of rhodopsin have not been prepared, precluding structural analysis using high resolution x-ray diffraction. Thus, the majority of experimental studies have utilized electronic absorption (6-10), resonance Raman (11,12), nuclear magnetic resonance (13), Fourier-transform IR (14-16), or picosecond spectroscopy (17, 18). The above-cited experimental, as well as theoretical (19-24), investigations are not in general agreement concerning the state of protonation of the chromophore (see, for example, refs. 2, 3, 5-8, 11-16, and 18-24) or the number and location of the counterions inside the binding site (2, 6-8, 18-21, 23). With the goal of resolving some of these issues, we report here the two-photon spectrum of locked-ilcis-rhodopsin.The unique diagnostic capabilities of two-photon spectroscopy for studying the binding site of rhodopsin derive in part from the unusual electronic properties of polyenes. [The polyene chromophore of rhodopsin is 11-cis-retinal bound to the opsin protein via a covalent linkage with the E-amino nitrogen of lysine (1)(2)(3)(4)(5) (27). The latter method, which is described in this paper, proved to be more reliable and is based on the previous synthetic work of Akita et al. (8). The incorporation of the locked-11-cis chromophore (shown in Fig. 1) into opsin produces a nonbleachable rhodopsin analog that can withstand the high light fluxes used in two-photon spectroscopy (9, 27). There is compelling evidence to suggest that the "locked" chromophore occupies the same binding site as the native 11-cis chromophore, and the spectroscopic (one-photon absorption and CD) similarities suggest that the counterion environment is unperturbed (8).The following sections describe the generation of the twophoton thermal lens spectrum and the theoretical analysis of the spectroscopic data. Our principal goal is to assign the state of protonation of the chromophore and determine the nature of the local counterion environment. 4117The publication costs of this article were defrayed in part by page c...

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Origins of inhomogeneous broadening in the vibronic spectra of visual chromophores and visual pigments

Cited by 65 publications

References 1 publication

(5‐demethyl)‐Bacteriorhodopsin analogue: its formation and light‐driven proton pump action

(5‐demethyl)‐Bacteriorhodopsin analogue: its formation and light‐driven proton pump action

Ab initiostudy on the low-lying excited states of retinal

Two-photon spectroscopy of locked-11-cis-rhodopsin: evidence for a protonated Schiff base in a neutral protein binding site.

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