種子由来キシログルカン多糖の溶液構造の解析

抄録

We have investigated in the structural properties of xyloglucans extracted from four kinds of seeds(Afzelia, Detarium, Jatoba, Tamarind) by static and dynamic light scattering measurement(SLS and DLS, respectively) and small angle X-ray scattering measurement(SAXS). The primary aim of this study is to clarify the origin of differences of the physiological activities or physicochemical properties shown by the xyloglucans extracted from different sources in term of the structure of xyloglucan in aqueous solution. From the experimental results of SLS and DLS measurements, the structure of xyloglucans extracted from all seeds is essentially the same and assumes random coil conformation. SAXS measurements confirm a rod-like structure common to xyloglucans. We propose the molecular model on the basis of a blob model. The scattering function of our model (I(q)) is described as a linear sum of two term as; I(q) = A(q)²[2(exp( - R_g²q²) - 1 + R_g²q²)⁄ (R_g²q²) + cξ²q²⁄(1 + cξ²q²)], where q is the magnitude of a scattering vector, A(q) is a scattering amplitude from xyloglucan single helix, R_g is the gyration radius of xyloglucan chain, c is a constant and ξ is a diameter of a blob. The scattering function proposed here can reproduce the experimental scattering profiles in whole measured q region including SLS and SAXS measurements. The significant differences are observed in the value of ξ among xyloglucans extracted from different seeds. Since ξ corresponds to Kuhn length according to the definition of ξ, the difference in the value of ξ indicates that the flexibility of xyloglucan extracted from different seed should be different. Thus, the differences in flexibility may be one of the origins for the different physiological activities or physicochemical properties shown by the xyloglucan extracted from different sources.