Kinetics of denaturation and renaturation processes of double-stranded helical polysaccharide, xanthan in aqueous sodium chloride

Yu Tomofuji; Koichi Matsuo; Ken Terao

doi:10.1016/j.carbpol.2021.118681

Kinetics of denaturation and renaturation processes of double-stranded helical polysaccharide, xanthan in aqueous sodium chloride

Carbohydr Polym. 2022 Jan 1:275:118681. doi: 10.1016/j.carbpol.2021.118681. Epub 2021 Sep 21.

Authors

Yu Tomofuji¹, Koichi Matsuo², Ken Terao³

Affiliations

¹ Department of Macromolecular Science, Graduate School of Science, Osaka University, 1-1, Machikaneyama-cho, Toyonaka, Osaka 560-0043, Japan. Electronic address: tomofujiy16@chem.sci.osaka-u.ac.jp.
² Hiroshiema Synchrotron Radiation Center, Hiroshima University, Kagamiyama, Higashi-hiroshima, Hiroshima 739-0046, Japan. Electronic address: pika@hiroshima-u.ac.jp.
³ Department of Macromolecular Science, Graduate School of Science, Osaka University, 1-1, Machikaneyama-cho, Toyonaka, Osaka 560-0043, Japan. Electronic address: kterao@chem.sci.osaka-u.ac.jp.

PMID: 34742411
DOI: 10.1016/j.carbpol.2021.118681

Abstract

Circular dichroism (CD) and small-angle X-ray scattering (SAXS) measurements were made for three xanthan samples, a double helical polysaccharide, in 5 or 10 mM aqueous NaCl after rapid temperature change to investigate the kinetics of the conformational change between the ordered and disordered states. After the rapid heating, the CD signal mainly reflecting the carbonyl groups on the side chains quickly changed (<150 s) while the scattering intensity from SAXS around q (magnitude of the scattering vector) = 1 nm^-1 changed more gradually, reflecting the main-chain conformation. The difference between CD and SAXS implies us the intermediate conformation which can be regarded as a loose double helix. The SAXS profile in the rapid cooling process showed that the loose double helical structure was constructed within 150 s, but the CD signal slowly changed with around 2 days to recover the native tight double helix.

Keywords: Circular dichroism; Conformational change; Double helix; Intermediate state; Small-angle X-ray scattering.

MeSH terms

Carbohydrate Conformation
Circular Dichroism / methods
Kinetics
Molecular Conformation
Polysaccharides, Bacterial / chemistry*
Scattering, Small Angle
Sodium Chloride / chemistry*
Temperature
Water / chemistry*
X-Ray Diffraction / methods

Substances

Polysaccharides, Bacterial
Water
Sodium Chloride
xanthan gum