Rh. Newman et Ja. Hemmingson, INTERACTIONS BETWEEN LOCUST BEAN GUM AND CELLULOSE CHARACTERIZED BY C-13 NMR SPECTROSCOPY, Carbohydrate polymers, 36(2-3), 1998, pp. 167-172
Molecular interactions between locust bean gum (LEG) and cellulose cry
stallite surfaces appear to involve most mannosyl residues of the mann
an backbone, not just the small proportion contained in long segments
which lack galactosyl residues. This conclusion is based on: (1) relat
ive strengths of C-13 n.m.r. signals at 102.2 ppm in the cross-polariz
ation (CP) spectrum and 101.3 ppm in the single-pulse excitation (SPE)
spectrum, assigned to mannosyl C-l in bound and non-bound segments of
LEG, respectively; (2) displacement of a C-13 n.m.r. signal assigned
to mannosyl C-4 to 81 ppm, indicating a change of conformation in the
mannan backbone relative to a gel phase; (3) similarities between prot
on spin relaxation time constants for cellulose and LEG, indicating pr
oton spin diffusion between polymers in close contact; (4) broadening
of CP n.m.r. signals at 83.9 and 85.0 ppm, assigned to C-4 of cellulos
e chains exposed on crystallite surfaces. The galactosyl C-1 signal ap
pears at 99.9 ppm in the SPE n.m.r. spectrum of the LEG-cellulose comp
lex but shows a poor response to CP n.m.r., indicating that galactosyl
residues are not fixed in rigid conformations relative to the mannan
backbones. (C) 1998 Elsevier Science Ltd. All rights reserved.