Global and internal molecular dynamics of poly(acrylamide-co-allyl 2-acetamido-2-deoxy-D-glucopyranoside) glycopolymers from ¹³C NMR relaxation studies

Abstract

."C spin-lattice and spin-spin relaxation times and nuclear Overhauser enhancements have been used to examine the molecular dynamics of the a-(1) and P-(2) anomeric forms of poly(acry1amide-co-ally1 2-acetamido-2-deoxy-D-glucopyranoside) glycopolymers. The timescale of motions and the spatial restriction of these motions were determined by using various forms of the "model-free" approach. It is shown that the motions of the C-H vectors of the polymer backbone may be described by a scaled Lorentzian spectral density function, giving rise to an effective correlation time for overall tumbling. The temperature dependence of this correlation time suggests that the overall motion is dependent on viscosity. The overall motion of the polymer molecules is shown to be anisotropic in nature by including the spinspin relaxation data in the analysis. The N-acetyl methyl and sugar hydroxymethyl (Ch) groups exhibit internal motions. The activation energies associated with these internal motions are derived. The difference in relaxation rates between the a and p anomeric forms, though small, suggests that the motions of the sugar ring may be different for the two systems. This conclusion is supported by potential energy contour map calculations, which indicate that the P anomer (2) has almost twice the conformational flexibility of the a anomer (1).RENE ROY, FRANCOIS D. TROPPER, ANTONY J. WILLIAMS et JEAN-ROBERT BRISSON. Can. J. Chem. 71, 1995Chem. 71, (1993.On a utilisk les temps de relaxation spin-rCseau et spin-spin en RMN du "C ainsi que des expCriences d'effets Overhauser nucleaires pour Ctudier la dynamique moleculaire des fonnes anomkres a (1) et P (2) des glycopolymkres poly(acry1amide- co-2-acetarnido-2-dCsoxy-~-glucopyranoside d'allyle). On a determink l'ordre de grandeur des vitesses des mouvements et de la restriction spaciale de ces mouvements en faisant appel i diverses fonnes de l'approche ((non-modklisCe)).On a montrC que l'on peut dkcrire les mouvement des vecteurs C-H de la structure de polymkre par une fonction de Lorentz de densite spectrale qui donne lieu B une correlation efficace du temps de renversement global. La relation entre la temperature et ce temps de corrClation suggkre que le mouvement global depend de la viscositC. En incluant les donnCes de relaxation spin-spin dans l'analyse, on montre que le mouvement global de la mol&cule est naturellement anisotrope. Les groupes N-acCtylmCthyle et hydromethyle (Ch) du sucre presentent des mouvements internes. On a dCduit les energies d'activation associees ii ces mouvements internes. Les differences dans les vitesses de relaxation entre les formes anomkres a et p, mcme si elles sont faibles, suggkrent que les mouvements du cycle du sucre peuvent ktre diffkrents pour les deux systkmes. Cette conclusion est en accord avec les calculs des cartes de contour de 1'Cnergie potentielle qui indiquent que la flexibilitk de l'anomkre P (2) est deux fois plus grandes que celle de l'anomkre a (1).[Traduit par la redaction]

Motional properties of a pentasaccharide containing a 2,6-branched mannose residue as studied by 13C nuclear spin relaxation

“…In the field of carbohydrate research, nuclear magnetic relaxation is frequently used to establish the motional behavior of different sugars Markley, 1986, 1987;Adams and Lerner, 1992;Hricovini et al, 1992;Poppe and Van Halbeek, 1992;Braccini et al, 1993;Hajduk et al, 1993;Roy et al, 1993;Dais, 1994;Poppe et al, 1994;Hricovini and Torri, 1995). Motional features of carbohydrates are important aspects in the understanding of the chemistry behind reactions with oligosaccharides.…”