Hydration of Cis and Trans N-Methylformamide as Revealed by the Use of O-17-Nmr, Molecular Mechanics, and Ab-Initio Calculations
Φόρτωση...
Ημερομηνία
Συγγραφείς
Gerothanassis, I. P.
Demetropoulos, I. N.
Vakka, C.
Τίτλος Εφημερίδας
Περιοδικό ISSN
Τίτλος τόμου
Εκδότης
Wiley-Blackwell
Περίληψη
Τύπος
Είδος δημοσίευσης σε συνέδριο
Είδος περιοδικού
peer reviewed
Είδος εκπαιδευτικού υλικού
Όνομα συνεδρίου
Όνομα περιοδικού
Biopolymers
Όνομα βιβλίου
Σειρά βιβλίου
Έκδοση βιβλίου
Συμπληρωματικός/δευτερεύων τίτλος
Περιγραφή
The solvation of cis and trans N-methylformamide (NMF) by water was investigated using a combination of O-17-nmr spectroscopy, classical molecular mechanics [MM2(77) and Mm2(87)] force field, and ab initio 4-31G* gradient optimization calculations. In dilute aqueous solution, the O-17-nmr spectra of NMF indicate strong shielding by 66.9 and 66.1 ppm for the cis and trans amide oxygens, respectively, compared to those values obtained in dilute toluene solution. This demonstrates that both isomers are equally solvated by molecules of water, which are further hydrogen bonded to molecules of water of the bulk solvent. Molecular mechanics simulations were carried out for cis and trans NMF in a cluster of water molecules. Radial distribution functions show structural contacts by several water molecules at the amide CO and NH group, which are significantly more pronounced with MM2(87) calculations. Ab initio 4-31G* gradient optimization calculations on the supermolecule trans NMF-(H2O)(3) indicates the presence of more than two hydrogen-bond contacts at the carbonyl oxygen. This is in agreement with MM2 calculations and provides further evidence for multiple acceptor properties of the amide oxygen and an out of the amide plane arrangement of the bound molecules of water. Comparison of the integration data to the first radial distribution function (rdf) minima shows that the local solvation of CO and NH groups is very similar for both cis and trans isomers. The intermolecular geometric parameters of the supermolecule trans NMA-(H2O)(3) and the first rdf maxima resulting from Mm2(87) and MM2(77) calculations are compared with distribution of water molecules around the CO and NH groups of peptides and proteins resulting from x-ray and neutron diffraction experiments. The rdfs involving the methyl group of NMF demonstrate the nonrandom distribution of solvent sites with first maxima in reasonable agreement with distribution water molecules around the apolar side chain of amino acid residues in proteins. (C) 1995 John Wiley & Sons, Inc.
Περιγραφή
Λέξεις-κλειδιά
intermolecular potential functions, nuclear magnetic-resonance, aqueous-solution, nmr-spectroscopy, chemical-shifts, monte-carlo, water, amides, solvation, crystals
Θεματική κατηγορία
Παραπομπή
Σύνδεσμος
<Go to ISI>://A1995RV63900004
http://onlinelibrary.wiley.com/store/10.1002/bip.360360405/asset/360360405_ftp.pdf?v=1&t=hmn3npgp&s=35a8143fd7018cc261394ad148f694f09f24890e
http://onlinelibrary.wiley.com/store/10.1002/bip.360360405/asset/360360405_ftp.pdf?v=1&t=hmn3npgp&s=35a8143fd7018cc261394ad148f694f09f24890e
Γλώσσα
en
Εκδίδον τμήμα/τομέας
Όνομα επιβλέποντος
Εξεταστική επιτροπή
Γενική Περιγραφή / Σχόλια
Ίδρυμα και Σχολή/Τμήμα του υποβάλλοντος
Πανεπιστήμιο Ιωαννίνων. Σχολή Θετικών Επιστημών. Τμήμα Χημείας