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 (Journal article)

Troganis, A./ Gerothanassis, I. P./ Athanassiou, Z./ Mavromoustakos, T./ Hawkes, G. E./ Sakarellos, C.

(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.
Institution and School/Department of submitter: Πανεπιστήμιο Ιωαννίνων. Σχολή Θετικών Επιστημών. Τμήμα Χημείας
Keywords: hydration,cis/trans isomerism,gradient enhanced h-1-nmr,c-13-nmr,noe,molecular dynamics,enthalpy,entropy,magnetic-resonance,free-energies,multidimensional nmr,protein hydration,solid-state,peptide,water,conformations,requirements,distances
ISSN: 0006-3525
Link: <Go to ISI>://000084335200007<72::AID-BIP7>3.0.CO;2-5/asset/7_ftp.pdf?v=1&t=hmn3kxpc&s=2ab5069f75ec5fce378b0315518e821572d40b0d
Publisher: Wiley-Blackwell
Appears in Collections:Άρθρα σε επιστημονικά περιοδικά ( Ανοικτά)

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