A High-Resolution Solid-State 13C NMR Study of the Secondary Structure of Linear (1→3)-β-d-Glucans: A Conformational Elucidation of Noncrystalline and Crystalline Forms by Means of Conformation-Dependent 13C Chemical Shifts

Abstract

The high-resolution solid-state 13C NMR spectra of annealed curdlan, a (1→3)-β-d-glucan, were recorded in order to obtain reference data on the 13C chemical shifts of the triple helix form, which would be useful for the conformational elucidation of two distinct noncrystalline forms, curdlan- and laminaran-types. It was found that the C-3 peak of crystalline annealed glucan is substantially displaced from that of noncrystalline starting powder, reflecting the conformational change. The laminaran-type conformation, which is found in either laminaran or a number of fungal branched glucans, was identical with the triple helix, judging from the similarity in the 13C NMR spectra, although the linewidths of the former are much larger than those of the latter. The curdlan-type form, on the other hand, was ascribed to the single helix form on the basis of the previous data on high-resolution 13C NMR. In addition, the 13C NMR spectra of crystalline paramylon showed a number of additional signals other than the peaks of triple-helical annealed curdlan, in spite of the similarity in the X-ray diffraction patterns.

Crystal transition of paramylon with dehydration and hydration

“…The spectra of dried and rehydrated samples are similar to the previously reported spectra (Fig. 3b and c) (Fyfe et al, 1984;Saito et al, 1987Saito et al, , 1989. On the other hand, some signals of the never-dried samples clearly split into more peaks than that of the rehydrated samples, although the peak positions of the two spectra are the same (Fig.…”

“…One of the peaks might be derived from crystalline region and the other from amorphous region. However, Saito et al (1987) reported that the relaxation time (T 1c ) of those two peaks was almost the same: 26 and 34 s; therefore it is impossible to assign one of them to amorphous region. Further study is required on this point.…”

“…3)-b-D-glucan has been studied by X-ray diffraction (Chuah, Sarko, Deslandes, & Marchessault, 1983; Deslandes, Marchessault, & Sarko, 1980;Marchessault, Deslandes, Ogawa, & Sundararajan, 1977;Takeda, Yasuoka, Kasai, & Harada, 1978) and solid-state 13 C NMR spectroscopy (Fyfe et al, 1984;Pelosi, Bulone, & Heux, 2006;Saito, Tabeta, & Harada, 1981;Saito, Tabeta, Yokoi, & Erata, 1987;Saito, Yokoi, & Yoshioka, 1989), mainly using curdlan as specimen. One reason for the interests in curdlan is its gelation phenomena in aqueous solutions (Harada et al, 1968;Marchessault et al, 1977;Saito et al, 1981Saito et al, , 1989.…”

Terraced self assembled nano-structures from laminarin

“…A member of the 1-3-␤-d-glucan family laminarin has a linear structure with a small degree of side branching. Laminarin is an uncharged polysaccharide at neutral pH, which has been shown to form a triple helical conformation under these conditions in water [5][6][7][8]. The structures reported in this study are formed by drying neutral pH solutions of laminarin onto clean mica.…”

Conformation and Dynamics of (1→3)-β-D-Glucans in the Solid and Gel State

“…It is pointed out that direct NMR observation of the solid-like domains has recently been made possible (14,15) by the development of a highly stable magic-angle spinning system using a rotor of the double air bearing type. In the present article, we summarize our previous results on conformation and dynamics of (1 -• 3)-/?-d-glucans in the solid and gel states (15)(16)(17)(18)(19)(20)(21)(22) by conventional and high-resolution solid-state 13 C NMR, with emphasis on revealing gelation mechanisms.…”