A "hidden" role of amino and imino groups is unveiled during the micro-solvation study of three biomolecule groups in water

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A "hidden" role of amino and imino groups is unveiled during the micro-solvation study of three biomolecule groups in water (EN)

Takis, P. G. (EN)

Πανεπιστήμιο Ιωαννίνων. Σχολή Θετικών Επιστημών. Τμήμα Χημείας (EL)
Takis, P. G. (EN)

The C-13 longitudinal relaxation times (T-1) of three biomolecule groups of major significance to proteins and cells - protein amino acids (AAs), acetyl-amino acids (Ac-AAs) and betaines - and the N-14 linewidths (Delta nu(1/2)) of Ac-AAs and betaines were measured in aqueous solutions at acidic and neutral pH, by NMR spectroscopy, to estimate the effect of the molecular weight (M-w) on C-13 longitudinal relaxation times and N-14 linewidths, respectively. C-13 relaxation times indicate that AAs and Ac-AAs strongly interact with the same number of water molecules at acidic and neutral pH, respectively, whereas both C-13 and N-14 results indicate that their Mw values at acidic pH (protonated, positively charged AAs and zero-charged Ac-AAs) increase relatively to those at pH 6.0 (zwitterionic AAs and negatively charged Ac-AAs) that translates into their extra hydration with an excess of one water molecule. Both C-13 and N-14 relaxation times revealed that betaines retain their hydration grade in both their ionization states at two pH values, while exhibiting their hydration differences from AAs and Ac-AAs and pointing out the "controlling" role of the amino and imino groups in the extra hydration of protonated AAs and Ac-AAs, enlightening the so far unknown significant role of the N-terminus and the -NH near the C-terminus in peptide solvation. Moreover, DFT calculations of the interacting water molecules through hydrogen bonds with Ala, Ac-Ala and Ala betaine molecules in their protonated and neutral pH forms are in absolute agreement with NMR results. Finally, a fully promising method arises with a view on hydration-solvation studies of oligopeptides and other bio-organic molecules by C-13 relaxation. (EN)

relative hydration numbers (EN)

New Journal of Chemistry (EN)



Springer Verlag (Germany) (EN)

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