In photosystem II, water oxidation occurs at the oxygen-evolving complex (OEC). The presence of a hydronium ion (HO) was proposed at the Cl binding site and Ca-depleted OEC. Using a quantum mechanical/molecular mechanical approach, we report the stability of HO in the PSII protein environment. Neither release of the proton from ligand water molecule W2 at the OEC nor formation of HO at Cl is energetically favorable. In contrast, HO can exist at the Ca-depleted OEC. Even when HO exists in Ca-depleted PSII, the H-bond network of the redox-active tyrosine (TyrZ) remains unaltered, retaining the unusually short low-barrier H-bond with D1-His190, and the redox potential of TyrZ, (TyrZ), remains unaltered. These observations explain why the oxidation of the Ca-depleted MnO cluster by TyrZ (i.e., the S to S transition) is not inhibited at low pH. It seems likely that Ca plays a role in not only (i) maintaining the H-bond network and facilitating TyrZ oxidation [tuning (TyrZ)] but also (ii) providing the valence of +2, decreasing the p of the ligand molecule (W1), and facilitating the release of the proton from W1 in the S to S transition together with Cl.
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http://dx.doi.org/10.1021/acs.biochem.0c00177 | DOI Listing |
J Phys Chem A
January 2025
Institut des Sciences Moléculaires, UMR CNRS 5255, Univ. Bordeaux, Talence cedex F-33405, France.
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View Article and Find Full Text PDFACS Nano
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School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798, Singapore.
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View Article and Find Full Text PDFJ Cell Mol Med
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Department of Botany and Microbiology, College of Science, King Saud University, Riyadh, Saudi Arabia.
This study explores novel therapeutic avenues for diabetes, a global health concern marked by elevated blood glucose levels. We investigated the anti-diabetic potential of Gymnema Sylvestre's bioactive compounds, including Gymnemic acid I, Stigmasterol, Deacylgymnemic acid, Beta-Amyrin acetate, Longispinogenin, Gymnemic acid II, Gymnemic acid, Gymnemic acid X, Gymnemaside VI, Phytic acid and Gymnemic acid X. Employing network pharmacology, molecular docking and molecular dynamics (MD), we elucidated the potential mechanism of action.
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INSERM U1248 Pharmacology & Transplantation, Univ. Limoges, CBRS, 2 Rue du Prof. Descottes, F-87000 Limoges, France.
Dry skin is a common condition that is experienced by many. Besides being particularly present during the cold season, various diseases exist all year round, leading to localized xerosis. To prevent it, the skin is provided with natural moisturizing factors (NMFs).
View Article and Find Full Text PDFAngew Chem Int Ed Engl
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CAS Key Laboratory of Design and Assembly of Functional Nanostructures, Fujian Provincial Key Laboratory of Nanomaterials, State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, 350002, Fujian, P. R. China.
N reduction reaction (NRR) by light is an energy-saving and sustainable ammonia (NH) synthesis technology. However, it faces significant challenges, including high energy barriers of N activation and unclear catalytic active sites. Herein, we propose a strategy of photo-driven ammonia synthesis via a proton-mediated photoelectrochemical device.
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