Carbon-13 Chemical Shifts of Retinal Isomers and Their Schiff Bases as Models of Visual Chromophores

Inoue, Yoshio; Tokitô, Yasuo; Tomonoh, Shigeki; Chûjô, Riichirǒ

doi:10.1246/bcsj.52.265

Cited by 11 publications

(13 citation statements)

References 11 publications

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“…This comparison reveals that the chemical shift changes of C12 and C14 are almost identical to those in model compounds. [45][46][47] The large shielding of C12 is a result of the reduced distance between C12 and C15 in 13-cis compared to all-trans retinal [45][46][47] , which was also verified under our experimental conditions (Fig. S7).…”

Section: K-statesupporting

confidence: 80%

Chromophore Distortions in Photointermediates of Proteorhodopsin Visualized by Dynamic Nuclear Polarization-Enhanced Solid-State NMR

et al. 2017

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Proteorhodopsin (PR) is the most abundant retinal protein on earth and functions as a light-driven proton pump. Despite extensive efforts, structural data for PR photointermediate states have not been obtained. On the basis of dynamic nuclear polarization (DNP)-enhanced solid-state NMR, we were able to analyze the retinal polyene chain between positions C10 and C15 as well as the Schiff base nitrogen in the ground state in comparison to light-induced, cryotrapped K- and M-states. A high M-state population could be achieved by preventing reprotonation of the Schiff base through a mutation of the primary proton donor (E108Q). Our data reveal unexpected large and alternating C chemical shift changes in the K-state propagating away from the Schiff base along the polyene chain. Furthermore, two different M-states have been observed reflecting the Schiff base reorientation after the deprotonation step. Our study provides novel insight into the photocycle of PR and also demonstrates the power of DNP-enhanced solid-state NMR to bridge the gap between functional and structural data and models.

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Section: K-statesupporting

confidence: 80%

Chromophore Distortions in Photointermediates of Proteorhodopsin Visualized by Dynamic Nuclear Polarization-Enhanced Solid-State NMR

et al. 2017

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“…The chemical shift changes are compared to those observed for the trans-cis isomerization in model compounds (gray bars in Fig. 4A ) ( 44 , 45 ). For the K-state, they deviate by more than 4 ppm for C10 to C13 and C20 between KR2 and model compounds, which therefore suggests a protein-induced chromophore distortion around these carbons in the K-state.…”

Section: Resultsmentioning

confidence: 99%

“… ( A ) Chemical shift differences between dark state (G) and photointermediates K, L, and O are plotted for carbon atoms C10 to C15, C20, and SB. The gray bars illustrate the effect of the all-trans 13-cis isomerization as observed for the model compounds N -retinylidenebutylamine (C10 to C15) and retinal (C20) ( 44 , 45 ). The 15 N chemical shift of KR2 in the dark and intermediate states is compared to GPR ( 37 ), BR ( 28 ), and ChR2 ( 36 ).…”

Section: Resultsmentioning

confidence: 99%

Probing the photointermediates of light-driven sodium ion pump KR2 by DNP-enhanced solid-state NMR

et al. 2021

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The functional mechanism of the light-driven sodium pump Krokinobacter eikastus rhodopsin 2 (KR2) raises fundamental questions since the transfer of cations must differ from the better-known principles of rhodopsin-based proton pumps. Addressing these questions must involve a better understanding of its photointermediates. Here, dynamic nuclear polarization–enhanced solid-state nuclear magnetic resonance spectroscopy on cryo-trapped photointermediates shows that the K-state with 13-cis retinal directly interconverts into the subsequent L-state with distinct retinal carbon chemical shift differences and an increased out-of-plane twist around the C14-C15 bond. The retinal converts back into an all-trans conformation in the O-intermediate, which is the key state for sodium transport. However, retinal carbon and Schiff base nitrogen chemical shifts differ from those observed in the KR2 dark state all-trans conformation, indicating a perturbation through the nearby bound sodium ion. Our findings are supplemented by optical and infrared spectroscopy and are discussed in the context of known three-dimensional structures.

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“…However, it has also been proposed that hydrogen bonding to thc Schiff base may be responsible for the bathochromic shift. 24 Consequently, acid-base properties of model Schiff bases have bccn studied and, in particular, changes in absorption spectra caused by altering the acid-base environment. The Schiff base resulting from the reaction of retinal with n-butylamine, i.c.…”

Section: Introductionmentioning

confidence: 99%

RELATIVE GROUND AND EXCITED STATE ENERGIES OF CH₃(CH=CH)₅CH=NC₄H₉, ITS HYDROGEN‐BONDED AND PROTON‐TRANSFERRED SPECIES, AND CHARGE PARTITIONING AND DISTRIBUTION IN THE PROTONATED SCHIFF BASE OF RETINAL*

Blatz

Tompkins

1993

Photochem & Photobiology

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CH3(CH = CH)5CH = NC4H9 (compound 1) is structurally related to the Schiff base of retinal, the prosthetic group in visual pigments. Dilute solutions of a weak acid (phenol) and 1 in a hydrocarbon solvent, when subjected to decreasing temperature, show striking changes in electronic absorption spectra. Initially only the spectrum of compound 1 is present, but as the temperature is lowered, the absorbance of 1 decreases, and the spectrum of the H-bonded form of 1 appears and increases. Continued temperature lowering then causes a decrease in absorption of the H-bonded form and an appearance and rise in absorption of the proton-transferred form of 1. Concentrations of the various species are measured as a function of temperature, and by standard procedures, the thermodynamic constants for both reaction steps are computed. Values of delta H0 are taken as relative energies among the three ground states, and the lambda max value of each species yields relative energies among excited states. By employing data from electronic absorption spectroscopy, nuclear magnetic resonance (NMR) and theoretical calculations for retinal Schiff base, charge partitioning between nitrogen and the polyene chain and charge distribution among the carbon atoms of the polyene chain are calculated.

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Carbon-13 Chemical Shifts of Retinal Isomers and Their Schiff Bases as Models of Visual Chromophores

Cited by 11 publications

References 11 publications

Chromophore Distortions in Photointermediates of Proteorhodopsin Visualized by Dynamic Nuclear Polarization-Enhanced Solid-State NMR

Chromophore Distortions in Photointermediates of Proteorhodopsin Visualized by Dynamic Nuclear Polarization-Enhanced Solid-State NMR

Probing the photointermediates of light-driven sodium ion pump KR2 by DNP-enhanced solid-state NMR

RELATIVE GROUND AND EXCITED STATE ENERGIES OF CH₃(CH=CH)₅CH=NC₄H₉, ITS HYDROGEN‐BONDED AND PROTON‐TRANSFERRED SPECIES, AND CHARGE PARTITIONING AND DISTRIBUTION IN THE PROTONATED SCHIFF BASE OF RETINAL*

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Carbon-13 Chemical Shifts of Retinal Isomers and Their Schiff Bases as Models of Visual Chromophores

Cited by 11 publications

References 11 publications

Chromophore Distortions in Photointermediates of Proteorhodopsin Visualized by Dynamic Nuclear Polarization-Enhanced Solid-State NMR

Chromophore Distortions in Photointermediates of Proteorhodopsin Visualized by Dynamic Nuclear Polarization-Enhanced Solid-State NMR

Probing the photointermediates of light-driven sodium ion pump KR2 by DNP-enhanced solid-state NMR

RELATIVE GROUND AND EXCITED STATE ENERGIES OF CH3(CH=CH)5CH=NC4H9, ITS HYDROGEN‐BONDED AND PROTON‐TRANSFERRED SPECIES, AND CHARGE PARTITIONING AND DISTRIBUTION IN THE PROTONATED SCHIFF BASE OF RETINAL*

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RELATIVE GROUND AND EXCITED STATE ENERGIES OF CH₃(CH=CH)₅CH=NC₄H₉, ITS HYDROGEN‐BONDED AND PROTON‐TRANSFERRED SPECIES, AND CHARGE PARTITIONING AND DISTRIBUTION IN THE PROTONATED SCHIFF BASE OF RETINAL*