蔗糖共溶质对琼脂-魔芋胶共混体系溶胶-凝胶转变过程流变学性质及结构形成动力学的影响

以琼脂-魔芋胶溶液共混体系为研究对象,考察添加蔗糖共溶质（质量分数0%、5%、10%、15%）对溶胶-凝胶转变过程弹性模量（G’）和黏性模量（G”）变化的影响,并通过对凝胶结构平均形成速度（average structure development rate,SDRa）、即时凝胶化速度（vg）、凝胶化加速度（αg）分析,探讨凝胶结构形成动力学。结果表明：低质量分数（0%～5%）蔗糖共溶质存在时可显著提高共混体系的G’、SDRa、vg及αg（P＜0.05）,共溶质质量分数高于5%后,此4 个特征值被降低。低质量分数蔗糖共溶质通过增加共混体系中琼脂分子间的氢键作用,促进琼脂分子形成双螺旋结构,显著降低高温区的活化能,进而交联形成细密、平整的网络结构,改善了共混体系凝胶的流变及质构凝胶特性。     

The Effect of Small Cosolutes that Mimic Molecular Crowding Conditions on the Stability of Triplexes Involving Duplex DNA

Triplex stability is studied in crowding conditions using small cosolutes (ethanol, acetonitrile and dimethylsulfoxide) by ultraviolet (UV), circular dichroism (CD) and nuclear magnetic resonance (NMR) spectroscopies. The results indicate that the triplex is formed preferentially when the triplex forming oligonucleotide (TFO) is RNA. In addition, DNA triplexes (D:D·D) are clearly less stable in cosolute solutions while the stability of the RNA triplexes (R:D·D) is only slightly decreased. The kinetic of triplex formation with RNA-TFO is slower than with DNA-TFO and the thermal stability of the triplex is increased with the salt concentration in EtOH-water solutions. Accordingly, RNA could be considered a potential molecule to form a stable triplex for regulatory purposes in molecular crowding conditions.