Chronakis I S, Borgström J, Piculell L
Physical Chemistry 1, Center for Chemistry and Chemical Engineering, Lund University, Sweden.
Int J Biol Macromol. 1999 Aug;25(4):317-28. doi: 10.1016/s0141-8130(99)00050-1.
Mixtures of locust bean gum (LBG) with kappa-carrageenan (KC) in 0.1 M aqueous solutions of the mixed salts NaI/CsI were investigated by cryo-transmission electron microscopy (cryo-TEM) and dynamic viscoelastic measurements. Previous studies have shown that as the cesium content is increased in such mixed salt solutions, a transition occurs from molecularly dispersed helices to 'superhelical rods' of KC. We now found that LBG stabilises the superhelical rods, shifting the transition to a lower content of Cs for the mixtures than for KC alone. The formation of superhelical rods was evidenced both by cryo-TEM images and by an onset of thermal hysteresis in the coil helix transition of KC. In the mixtures, the transition temperatures on cooling and heating were insensitive to the proportions of LBG and KC present at all cesium contents. Under conditions where no helix aggregation occurred (no hysteresis) the mixtures showed high tan delta values and low storage moduli. Under aggregated conditions, gels formed, and gels with added LBG had enhanced moduli compared to gels with KC alone. On the basis of these results we propose that LBG associates to the super-helical rods of KC.
采用低温透射电子显微镜（cryo-TEM）和动态粘弹性测量方法，对刺槐豆胶（LBG）与κ-卡拉胶（KC）在0.1M NaI/CsI混合盐水溶液中的混合物进行了研究。先前的研究表明，随着此类混合盐溶液中铯含量的增加，KC会从分子分散的螺旋结构转变为“超螺旋棒”。我们现在发现，LBG能稳定超螺旋棒，使混合物的转变发生时所需的铯含量低于单独的KC。低温透射电子显微镜图像以及KC的螺旋-线圈转变中热滞现象的出现都证明了超螺旋棒的形成。在混合物中，冷却和加热时的转变温度对所有铯含量下LBG和KC的比例均不敏感。在未发生螺旋聚集的条件下（无热滞现象），混合物的损耗因子值较高而储能模量较低。在聚集条件下会形成凝胶，与仅含KC的凝胶相比，添加了LBG的凝胶模量更高。基于这些结果，我们提出LBG与KC的超螺旋棒缔合。
