Thermodynamic origin of cis/trans isomers of a proline-containing beta-turn model dipeptide in aqueous solution: A combined variable temperature H-1-NMR, two-dimensional H-1,H-1 gradient enhanced nuclear Overhauser effect spectroscopy (NOESY), one-dimensional steady-state intermolecular C-13,H-1 NOE, and molecular dynamics study

 
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2000 (EN)
Thermodynamic origin of cis/trans isomers of a proline-containing beta-turn model dipeptide in aqueous solution: A combined variable temperature H-1-NMR, two-dimensional H-1,H-1 gradient enhanced nuclear Overhauser effect spectroscopy (NOESY), one-dimensional steady-state intermolecular C-13,H-1 NOE, and molecular dynamics study (EN)

Troganis, A. (EN)

Πανεπιστήμιο Ιωαννίνων. Σχολή Θετικών Επιστημών. Τμήμα Χημείας (EL)
Troganis, A. (EN)

(H2O) C-13, H-1 NOE indicates that the water accessibility of the acetyl carbonyl carbons is nearly the same for both isomers. This is consistent with rapid fluctuations of the conformational ensemble and the absence of a highly shielded acetyl oxygen from the bulk solvent. Variable temperature H-1-nmr studies of the cis/trans conformational equilibrium indicate that the trans form is enthalpically favored (Delta H degrees = -5.14 KJ mole(-1)) and entropically (Delta S degrees = -5.47 J . K-1 mole(-1)) disfavored relative to the cis form. This demonstrates that, in the absence of strongly stabilizing sequence-specific interresidue interactions involving side chains and/or charged terminal groups, the thermodynamic difference of the cis/trans isomers is due to the combined effect of intramolecular and intermolecular (hydration) induced conformational changes. (C) 2000 John Wiley & Sons, Inc. (EN)

hydration (EN)

Πανεπιστήμιο Ιωαννίνων (EL)
University of Ioannina (EN)

Biopolymers (EN)

English

2000

<Go to ISI>://000084335200007

Wiley-Blackwell (EN)



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