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Absorption wavelength along chromophore low-barrier hydrogen bonds.

ABSTRACT: In low-barrier hydrogen bonds (H-bonds), the pK _a values for the H-bond donor and acceptor moieties are nearly equal, whereas the redox potential values depend on the H⁺ position. Spectroscopic details of low-barrier H-bonds remain unclear. Here, we report the absorption wavelength along low-barrier H-bonds in protein environments, using a quantum mechanical/molecular mechanical approach. Low-barrier H-bonds form between Glu46 and p-coumaric acid (pCA) in the intermediate pR_CW state of photoactive yellow protein and between Asp116 and the retinal Schiff base in the intermediate M-state of the sodium-pumping rhodopsin KR2. The H⁺ displacement of only ∼0.4 Å, which does not easily occur without low-barrier H-bonds, is responsible for the ∼50 nm-shift in the absorption wavelength. This may be a basis of how photoreceptor proteins have evolved to proceed photocycles using abundant protons.

SUBMITTER: Tsujimura M

PROVIDER: S-EPMC9062252 | biostudies-literature | 2022 May

REPOSITORIES: biostudies-literature

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Absorption wavelength along chromophore low-barrier hydrogen bonds.

Tsujimura Masaki M Tamura Hiroyuki H Saito Keisuke K Ishikita Hiroshi H

iScience 20220413 5

In low-barrier hydrogen bonds (H-bonds), the pK a values for the H-bond donor and acceptor moieties are nearly equal, whereas the redox potential values depend on the H+ position. Spectroscopic details of low-barrier H-bonds remain unclear. Here, we report the absorption wavelength along low-barrier H-bonds in protein environments, using a quantum mechanical/molecular mechanical approach. Low-barrier H-bonds form between Glu46 and p-coumaric acid (pCA) ...[more]

PMID: 35521532

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