Evidence of three distinct conformations—single chain, single helix, and triple helix—of (1 → 3)-β-D-xylan in the solid and intact frond of green algae as studied by 13C-nmr spectroscopy
✍ Scribed by Hazime Saitô; Junko Yamada; Yuko Yoshioka; Yûkô Shibata; Tomoki Erata
- Publisher
- Wiley (John Wiley & Sons)
- Year
- 1991
- Tongue
- English
- Weight
- 600 KB
- Volume
- 31
- Category
- Article
- ISSN
- 0006-3525
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✦ Synopsis
High-resolution solid-state 13C-nmr spectra of ( 1 + 3 ) -P-D-xylan from Bryopsis maxima and Caulerpa brachypus were recorded for various preparations from intact through dried frond to anhydrous and hydrated xylan, to gain insight into their secondary structures as compared with those of ( 1 + 3) -P-D-glucans. It turned out that l3C-nmr peaks of intact or dried frond were mainly ascribed to the peaks from (1 --+ 3 ) -0-D-linked xylose residue, although some peaks were seen a t the carbonyl and aliphatic regions. Dehydration of frond by either air drying or ethanol, and extraction of xylan with acid, did not result in substantial spectral change, although extraction with saturated ZnC12 solution caused appreciable displacements of the c -3 as well as c -2 and c -5 peaks. This means that no major conformational change was induced during the above-mentioned processes of the dehydration and the extraction with acid. The extraction with ZnCIP solution, however, induced major conformational change. Thus, we found that the above-mentioned three distinct conformationstriple helix, single helix, and single chain-are also present in ( 1 + 3 ) -P-D-xylan, as judged from the conformation-dependent displacements of I3C chemical shifts, hydration/dehydration-induced spectral change, and the x-ray diffraction data on Penicillus dumetosus by Atkins et al. In particular, we found that all the preparations except for the extraction with ZnClp solution retain the triple helix form, whereas the anhydrous and hydrate samples of the latter preparations take the single-chain and single-helix form, respectively. Further, we measured the "C spin-lattice relaxation times of laboratory frame of the xylan to gain insight into better understanding of the role of the hydroxymethyl group as an efficient relaxation pathway in ( 1 + 3 ) -8-D-glucan.