%0 Journal Article
%T Interplay between secondary structure and ion binding upon thermoreversible gelation of κ-carrageenan.
%A Makshakova ON
%A Faizullin DA
%A Zuev YF
%J Carbohydr Polym
%V 227
%N 0
%D Jan 2020 1
%M 31590886
%F 10.723
%R 10.1016/j.carbpol.2019.115342
%X It is widely accepted that cation binding specifically favors chain ordering and gelling of κ-carrageenan. However, current insights into the exact sequence of binding and conformational rearrangements as well as into the structure of binding sites are controversial. In the present work, the FTIR-spectroscopy combined with the computer modelling has been used to reveal the relation between cation binding and the secondary structure transition upon thermoreversible gelation of the κ-carrageenan. Three states of sulfate groups were defined spectroscopically: one cation-free and two specific cation-bound states. The DFT calculations reveal two energetically inequivalent spatial structures of cation binding unit, formed due to the local conformational adjustment in neocarrabiose moiety. Besides a charge screening effect, the cation-bound conformation of neocarrabiose also favors the helix formation.