scholarly journals Photo-induced Proton Transfers of Microbial Rhodopsins

10.5772/34105 ◽  
2012 ◽  
Author(s):  
Takashi Kikukawa ◽  
Jun Tamogami ◽  
Kazumi Shimono ◽  
Makoto Demura ◽  
Toshifumi Nara ◽  
...  
Keyword(s):  
Proton Transfers

Intramolecular Proton Transfer in the Isomerization of Hydroxyacetone: A Detailed Characterization Based on Reaction Force Analysis and the Bond Fragility Spectrum

2020 ◽  
Author(s):  
Wallace Derricotte ◽  
Huiet Joseph
Keyword(s):  
Chemical Potential ◽  
Reaction Force ◽  
Intramolecular Proton Transfer ◽  
Intermediate Energy ◽  
Force Analysis ◽  
Activation Energy Barrier ◽  
Detailed Characterization ◽  
Proton Transfers ◽  
Reaction Force Constant

The mechanism of isomerization of hydroxyacetone to 2-hydroxypropanal is studied within the framework of reaction force analysis at the M06-2X/6-311++G(d,p) level of theory. Three unique pathways are considered: (i) a step-wise mechanism that proceeds through formation of the Z-isomer of their shared enediol intermediate, (ii) a step-wise mechanism that forms the E-isomer of the enediol, and (iii) a concerted pathway that bypasses the enediol intermediate. Energy calculations show that the concerted pathway has the lowest activation energy barrier at 45.7 kcal mol<sup>-1</sup>. The reaction force, chemical potential, and reaction electronic flux are calculated for each reaction to characterize electronic changes throughout the mechanism. The reaction force constant is calculated in order to investigate the synchronous/asynchronous nature of the concerted intramolecular proton transfers involved. Additional characterization of synchronicity is provided by calculating the bond fragility spectrum for each mechanism.

scholarly journals Stepwise Hydrogen Atom and Proton Transfers in Dioxygen Reduction by Aryl-Alcohol Oxidase

Biochemistry ◽  
2018 ◽  
Vol 57 (11) ◽  
pp. 1790-1797 ◽  
Author(s):  
Juan Carro ◽  
Patricia Ferreira ◽  
Angel T. Martínez ◽  
Giovanni Gadda
Keyword(s):  
Hydrogen Atom ◽  
Alcohol Oxidase ◽  
Dioxygen Reduction ◽  
Proton Transfers

Reactive mode composition factor analysis of transition states: the case of coupled electron–proton transfers

2019 ◽  
Vol 21 (45) ◽  
pp. 24912-24918 ◽  
Author(s):  
Mauricio Maldonado-Domínguez ◽  
Daniel Bím ◽  
Radek Fučík ◽  
Roman Čurík ◽  
Martin Srnec
Keyword(s):  
Factor Analysis ◽  
Kinetic Energy ◽  
Isotope Effects ◽  
Transition States ◽  
Kinetic Isotope Effects ◽  
Composition Factor ◽  
Kinetic Isotope ◽  
Proton Transfers ◽  
Relative Kinetic ◽  
Reactive Mode

The kinetic energy distribution in the reactive mode in transition states correlates the asynchronicity of CPET with relative kinetic isotope effects.

scholarly journals Bacteriorhodopsin-like channelrhodopsins: Alternative mechanism for control of cation conductance

2017 ◽  
Vol 114 (45) ◽  
pp. E9512-E9519 ◽  
Author(s):  
Oleg A. Sineshchekov ◽  
Elena G. Govorunova ◽  
Hai Li ◽  
John L. Spudich
Keyword(s):  
Proton Translocation ◽  
Laser Flash ◽  
Cation Channel ◽  
Alternative Mechanism ◽  
Cytoplasmic Channel ◽  
Cation Conductance ◽  
Proton Transfers ◽  
Channel Opening ◽  
Guillardia Theta ◽  
Tightly Coupled

The recently discovered cation-conducting channelrhodopsins in cryptophyte algae are far more homologous to haloarchaeal rhodopsins, in particular the proton pump bacteriorhodopsin (BR), than to earlier known channelrhodopsins. They uniquely retain the two carboxylate residues that define the vectorial proton path in BR in which Asp-85 and Asp-96 serve as acceptor and donor, respectively, of the photoactive site Schiff base (SB) proton. Here we analyze laser flash-induced photocurrents and photochemical conversions in Guillardia theta cation channelrhodopsin 2 (GtCCR2) and its mutants. Our results reveal a model in which the GtCCR2 retinylidene SB chromophore rapidly deprotonates to the Asp-85 homolog, as in BR. Opening of the cytoplasmic channel to cations in GtCCR2 requires the Asp-96 homolog to be unprotonated, as has been proposed for the BR cytoplasmic channel for protons. However, reprotonation of the GtCCR2 SB occurs not from the Asp-96 homolog, but by proton return from the earlier protonated acceptor, preventing vectorial proton translocation across the membrane. In GtCCR2, deprotonation of the Asp-96 homolog is required for cation channel opening and occurs >10-fold faster than reprotonation of the SB, which temporally correlates with channel closing. Hence in GtCCR2, cation channel gating is tightly coupled to intramolecular proton transfers involving the same residues that define the vectorial proton path in BR.

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