聚电解质构象变化及其嵌段共聚物组装动力学的研究

Changes of ion concentration in aqueous solution can cause conformational transition of polyelectrolytes and formation or dissolution of micelles of polyelectrolyte block copolymers. The kinetics of the conformational transition of polyelectrolyte can help us to understand the effect of different interactions on the conformational transition of biomacromolecules. In early studies stopped flow technique has been used to follow the kinetics of the transition, but because of the limitation of this technique, early events less than one millisecond have not been investigated. We propose that under the irradiation by pulsed UV laser and by use of two water-soluble compounds and a caged calcium compound, the pH value and the concentration of calcium can be changed in less than one millisecond. Then the conformational transition of the polyelectrolytes and formation or dissolution of micelles of polyelectrolyte block copolymers can be followed by measurement of the fluorescence intensity, light scattering intensity and the absorbance. We will focus on the effect of the amplitude of the pH jump, ionic concentration and molecular weight. The outcome of the research is that an experimental method will be developed to study the kinetics of the conformational transition of polyelectrolytes and we will have a better understanding of the kinetics of the conformational transition of polyelectrolytes which will help us to understand much more sophisticated systems of charged biomacromolecules such as proteins and DNA.

改变离子浓度可导致聚电解质构象发生变化，从而使得含聚电解质嵌段的共聚物胶束形成或者解散。研究聚电解质构象变化的动力学过程可使我们深入了解生物大分子构象变化及其组装。由于触发手段的局限，如停流法，在水溶液中尚未能观察到亚毫秒的动力学快过程。本项目提出了，分别利用两种水溶性小分子及螯合的钙离子在脉冲紫外激光的作用下可在亚毫秒内实现溶液的pH和钙离子浓度跃变，结合相应体系中荧光、散射光和透射光强度的变化研究聚电解质构象转变和嵌段共聚物胶束的形成和解散动力学。着重研究pH跃变幅度、离子强度和分子量等因素对这些动力学过程的影响。通过该项目的完成，我们不仅可以发展一种研究聚电解质构象变化动力学的实验方法，而且可以测得并深入认识各个实验条件对聚电解质构象转变和组装动力学的影响，为利用动力学控制构象和组装提供理论基础。

改变离子浓度可导致聚电解质构象发生变化，从而使得含聚电解质嵌段的共聚物胶束形成或者解散。研究聚电解质构象变化的动力学过程可使我们深入了解生物大分子构象变化及其组装。由于触发手段的局限，如停流法，在水溶液中尚未能观察到亚毫秒的动力学快过程。通过本基金的资助，我们自行设计并搭建了一套脉冲激光诱导pH跃变结合散射光和荧光检测的仪器，该仪器可使水溶液中的pH值瞬间跃迁3个单位，pH跃迁幅度可控，并且仪器死时间比常规的停流仪低一个数量级；利用该仪器，我们研究了pH跃迁幅度以及溶液中离子种类和强度对两种pH响应型嵌段共聚物的解散动力学的影响，说明该仪器能很好地研究亚毫秒到秒量级的动力学过程；另外，我们还利用分析型超速离心和激光光散射等方法研究了静电相互作用和氢键等相互作用在聚电解质构象转变中所起的作用。依托本项目的资助，共发表包括Macromolecules, Soft Matter和Journal of Physical Chemistry在内的SCI论文14篇，指导3名博士研究生，其中2人已通过答辩，1人在研。