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The structure of gellan in dilute aqueous solution
Author(s) -
Bosco M.,
Miertus S.,
Dentini M.,
Segre A.L.
Publication year - 2000
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/1097-0282(200008)54:2<115::aid-bip4>3.0.co;2-w
Subject(s) - chemistry , rhamnose , residue (chemistry) , aqueous solution , conformational isomerism , nuclear overhauser effect , nmr spectra database , spectral line , nuclear magnetic resonance spectroscopy , crystallography , stereochemistry , molecule , organic chemistry , physics , astronomy , galactose
A full assignment of high‐field nmr spectra of gellan was obtained in dilute aqueous solution by performing a series of selective one‐dimensional nmr experiments. The observed nuclear Overhauser effects (NOEs) cannot be interpreted assuming that each sugar residue is intrinsically rigid and in a chair conformation. In fact, the rhamnose residue gives strong NOE contacts coherent only with an equilibrium involving both a chair as well as a boat (or a hemiboat) conformation. Molecular dynamic calculations performed on a heptamer with a central rhamnose support the above finding, and show a structure based on a very stiff single chain in which it is present a flipping of the rhamnose residue. At low temperatures (5–20°C) in very dilute solutions (0.018 mg/mL) nmr spectra show a splitting of the resonance due to the methyl group of rhamnose residue, thus confirming the presence of a slow equilibrium among different conformers. © 2000 John Wiley & Sons, Inc. Biopoly 54: 115–126, 2000