Conformational Properties of Flaxseed Rhamnogalacturonan-I and Correlation between Primary Structure and Conformation

Abstract

The pectic polysaccharides extracted from flaxseed (Linum usitatissiumum L.) mucilage and kernel were characterized as rhamnogalacturonan-I (RG-I). In this study, the conformational characteristics of RG-I fractions from flaxseed mucilage and kernel were investigated, using a Brookhaven multi-angle light scattering instrument (batch mode) and a high-performance size exclusion chromatography (HPSEC) system coupled with Viscotek tetra-detectors (flow mode). The Mw of flaxseed mucilage RG-I (FM-R) was 285 kDa, and the structure-sensitive parameter (ρ) value of FM-R was calculated as 1.3, suggesting that the FM-R molecule had a star-like conformation. The Mw of flaxseed kernel RG-I (FK-R) was 550 kDa, and the structure-sensitive parameter (ρ) values ranged from 0.90 to 1.21, suggesting a sphere to star-like conformation with relatively higher segment density. The correlation between the primary structure and conformation of RG-I was further discussed to better understand the structure–function relationship, which helps the scale-up applications of pectins in food, pharmaceutical, or cosmetic industries.

Rhamnogalacturonan I with β-(1,4)-Galactan Side Chains as an Ever-Present Component of Tertiary Cell Wall of Plant Fibers

“…The hydrodynamic radius of the aggregates formed by these polysaccharides is close and varies for common bean RG-I from 100 to 130 nm and for flax RG-I from 140 to 190 nm [19]. This is more than three-times smaller than the size of the aggregates formed in water by rhamnogalacturonans from flaxseed mucilage, characterized by a different position of rhamnose substitution (at O-3 instead of O-4), extremely short side chains, and the presence of both HG fragments and homorhamnan in the backbone [46]. But this size is, for example, almost twice as large as the size of aggregates formed in water by mixed-linkage glucan with flexible kinks in the structure of the chain [47].…”