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Spectroscopic Evidences for Strong Hydrogen Bonds with Selenomethionine in Proteins

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journal contribution
posted on 01.02.2017 by V. Rao Mundlapati, Dipak Kumar Sahoo, Sanat Ghosh, Umesh Kumar Purame, Shubhant Pandey, Rudresh Acharya, Nitish Pal, Prince Tiwari, Himansu S. Biswal
Careful protein structure analysis unravels many unknown and unappreciated noncovalent interactions that control protein structure; one such unrecognized interaction in protein is selenium centered hydrogen bonds (SeCHBs). We report, for the first time, SeCHBs involving the amide proton and selenium of selenomethionine (Mse), i.e., amide–N–H···Se H-bonds discerned in proteins. Using mass selective and conformer specific high resolution vibrational spectroscopy, gold standard quantum chemical calculations at CCSD­(T), and in-depth protein structure analysis, we establish that amide–N–H···Se and amide–N–H···Te H-bonds are as strong as conventional amide–NH···O and amide–NH···OC H-bonds despite smaller electronegativity of selenium and tellurium than oxygen. It is in fact, electronegativity, atomic charge, and polarizability of the H-bond acceptor atoms are at play in deciding the strength of H-bonds. The amide–N–H···Se and amide–N–H···Te H-bonds presented here are not only new additions to the ever expanding world of noncovalent interactions, but also are of central importance to design new force-fields for better biomolecular structure simulations.