Effects of water chemistry and concentrations of dissolved organic matter on its fluorescence characteristics and molecular conformation

Previous studies showed that water chemistry and concentrations of dissolved organic matter (DOM) could affect its molecular conformation and binding characteristics with hydrophobic organic contaminants (HOCs). However, the conformational change of DOM resultant from water chemistry and concentrations of DOM was not extensively investigated; therefore, the contradictory reports regarding the binding property with HOCs were available in literature. In this study, the effects of ionic strength, pH and DOM concentrations on the fluorescence properties of two humic acids (HA), namely Fluka HA and Amherst HA, were investigated by three-dimensional excitation-emission matrix fluorescence spectroscopy (3DEEM) and steady-state fluorescence polarization (FP) techniques. The results not only corroborated previous observations obtained by other investigators, but revealed some new information about the fluorescence properties and molecular conformation of the humic acids under different water chemistry and DOM concentration conditions, which could shed light on its binding mechanisms and binding properties with HOCs.     

多检测器凝胶渗透色谱法测定卡拉胶分子量及其稀溶液构象分析

本文采用三检测器联用凝胶色谱法对κ-型、ι-型卡拉胶的分子量进行测量（κ-型、ι-型卡拉胶的分子量分别为685.77 kDa和408.33 kDa）。通过研究两种卡拉胶稀溶液的Mark-Houwink指数、流体力学直径,得出了κ-型和ι-型卡拉胶的分子构象：在低分子量阶段,卡拉胶分子链刚性较强,呈现刚性棒状结构;在中分子量阶段,卡拉胶分子链的刚性降低,构象介于无规线团与刚性棒状结构之间,呈现半刚性的伸展线团;在高分子量阶段,卡拉胶分子呈现出无规线团构象。随着卡拉胶分子量的增加,卡拉胶分子链的刚性逐渐降低,卡拉胶分子由刚性棒状结构变为半刚性延展线团最终变为柔性无规线团,且κ-型和ι-型卡拉胶分子链表现出相同的变化趋势。卡拉胶的分子量和构象对卡拉胶的抗菌抗凝等生物活性以及纺丝性能有着较大的影响,对卡拉胶分子量和构象进行准确分析可以促进卡拉胶在纺织、医药、化妆品等工业生产中的应用。