Bola表面活性剂（G₂D）及复配体系中核黄素的光物理和光化学性质研究

【作者】 鲜树雍；

【导师】 郭荣；

【作者基本信息】 扬州大学 ， 物理化学， 2010， 硕士

【摘要】 1. 1, 12-二谷氨酸基十二烷基二胺盐的合成及复配研究合成了一种具有生物适应性的Bola型表面活性剂1,12-二谷氨酸基十二烷基二胺盐(G2D)和单链型的表面活性剂谷氨酸基十二烷基铵盐(GDA),并通过核磁、红外光谱,元素分析等方法对它们的结构进行了鉴定。此外,通过表面张力、等温滴定微量量热法等实验手段测定了G2D的临界胶束浓度、胶束聚集数、胶束的流体力学半径等。研究发现:与传统的单链表面活性剂GDA相比,Bola型表面活性剂G2D的表面活性较低,其表面张力曲线出现了两个转折点,对应的临界二聚体浓度(cdc)和临界胶束浓度(cmc)分别是7 mmol?L-1、17 mmol?L-1。将G2D和GDA混合后,经负染透射电镜证实,在一定复配比例条件下体系中有囊泡和链珠状聚集体存在。并且随着表面活性剂总浓度、复配比例、温度的改变,不同的聚集体结构之间可以相互转化和共存。根据实验结果,提出了G2D和GDA的相互作用及其聚集形貌的形成机理,并进一步通过微量量热、荧光光谱、核磁等实验手段对提出的机理进行验证。2.表面活性剂溶液中核黄素的光物理和光化学性质以G2D、GDA胶束水溶液和G2D/GDA复配形成的囊泡体系模拟仿生细胞膜,以核磁共振、等温滴定微量量热法、紫外光谱、荧光光谱、时间分辨荧光光谱法等方法研究了这三种分子有序组合体中核黄素的光物理和光化学性质。结果表明:随着胶束的形成,被增溶的核黄素自发地定位于G2D胶束的疏水碳氢链附近,它们的相互作用是放热过程。紫外光照条件下,核黄素在G2D溶液中发生光还原反应的速率常数与G2D的浓度有关。同时实验还证实表面活性剂的极性头基在核黄素与表面活性剂的相互作用中起决定性作用。在单头基的GDA胶束中,核黄素本身的光物理性质发生更为显著地变化,且核黄素与GDA分子间的强静电吸引作用使得GDA胶束结构变得更为松散。为考察体系微环境的影响,实验进一步研究了G2D/GDA复配体系中核黄素的光物理和光化学性质。结果表明:当摩尔比从15:1变到1:15时,体系由囊泡向链珠状聚集体转变,体系中核黄素的荧光和紫外强度都呈先降低再增大的趋势。在紫外光照条件下,核黄素在复配体系中发生光还原反应的速率同样与聚集体的形貌有关,链珠状聚集体比球形囊泡更有利于核黄素光反应的进行。3.表面活性剂溶液中核黄素与血红蛋白的相互作用利用荧光光谱、紫外吸收光谱、圆二色光谱等技术比较性研究了两种表面活性剂G2D、GDA与血红蛋白的相互作用。研究表明:G2D和GDA都可以结合在血红蛋白上。随着这两种表面活性剂浓度的增大,血红蛋白开始解螺旋,疏水空腔逐渐打开,血红蛋白逐渐变性。在G2D、GDA的血红蛋白溶液中加入核黄素后,核黄素与血红蛋白之间通过形成1:1型的复合物而猝灭血红蛋白的内源荧光,温度升高不利于该过程的进行。根据F?rster非辐射能量转移理论,得到G2D和GDA溶液中核黄素与血红蛋白分子间的能量转移效率、结合距离等。这不仅丰富了生物大分子与小分子之间相互作用的研究内容,为研究核黄素在活体细胞中的作用机制提供了可靠的实验数据,同时实验结果也对进一步理解血红蛋白的结构和功能关系提供了重要的理论依据。更多还原

【Abstract】 1. Synthesis and mixing behavior of 1, 12-diglutamic diaminododecaneA novel bolaform surfactant 1,12-diglutamic diaminododecane (G2D) and its counterpart n-dodecylammonium glutamate (GDA) with biodegradability and biological compatibility, have been synthesized and characterized by DSC, FT-IR, 1HNMR and elementary analysis measurements. The critical micelle concentration (cmc), the aggregation number and the average radius of the micelles of G2D are investigated by surface tension, isothermal titration microcalorimetry and dynamic light scattering experiments. Compared with its counterpart (GDA), G2D has lower surface activity and the values of critical dimer concentration (cdc) and critical micelle concentration (cmc) obtained from the surface tension curve are 7 mmol?L-1 and 17 mmol?L-1, respectively. Besides, the GDA and G2D mixing behavior is also studied. The coexistence of vesicles and beads aggregate is proved by the negative staining-TEM results. Another striking feature of this mixing system is that the vesicle formation and transformation can be adjusted by different factors, including the total surfactant concentration, the mixing molar ratios, and increase of temperature. Finally the mechanism to explain the interaction between the GDA and G2D is introduced and verified by mehtods of dynamic light scattering, fluorescence spectroscopy, nuclear magnetic resonance technology and isothermal titration microcalorimetry.2. Photophysical and photochemical properties of riboflavin in surfactant solutionsThe photophysical and photochemical properties of riboflavin have been undertaken in biomimetic systems formed by glutamic surfactants of different headgroups, namely G2D, GDA, and G2D/GDA mixed systems, using NMR, ITC, fluorescence, UV-vis absorption, time-resolved fluorescence spectroscopy. The results demonstrate that in the G2D micelles, riboflavin can spontaneously locate in the hydrophobic region formed by the hydrocarbon chain of G2D, which is an exothermic process. Ultraviolet illumination of riboflavin in G2D solution leads to the photo reduction of riboflavin and the reaction rate is dependent on the concentration of G2D. It is also confirmed from the parallel experiments that variation in the surfactant headgroup plays an important role in promoting a specific structural dynamism of the fluorophore of riboflavin. In GDA solution, the photophysical property of riboflavin shows greater change and the strong electrostatic interaction can further induce the loose of GDA micelle structure. In order to investigate the influence of polarity and viscosity of the microenvironments around the riboflavin molecules, the photophysical and photochemical properties of riboflavin in G2D/GDA mixed systems are further studied. The maximum absorbance and the fluorescence intensity of riboflavin in G2D/GDA mixed systems show tendency to ascend and followed to descend when the mixed molar ratios vary from 15:1 to 1:15, corresponding to the transformation from vesicles to beads aggregate. Meanwhile the photo reduction rates of riboflavin in G2D/GDA solutions are also related to the aggregation morphology, that is the beads aggregate favors the photochemical reaction of riboflavin under the illumination of UV light source.3. The interaction between riboflavin and hemoglobin in surfactant solutionsThe protein-surfactant systems constituted by G2D/Hb and GDA/Hb have been studied by using UV-vis absorption, steady-state fluorescence, and circular dichroism (CD) spectroscopy. It is found that the presence of G2D or GDA could induce the denature of hemoglobin. On the basis of previous experiment, the interaction of riboflavin with hemoglobin in G2D, and GDA are comparatively investigated. Riboflavin can quench the intrinsic fluorescence of Hb by the formation of 1:1 complex, which is unfavourable at higher temperature. The averaged binding distance and the energy transfer efficiency between riboflavin and Hb are calculated according to the theory of F?rster’s non-radiation energy transfer. This research can not only enrich the systems about the interaction between biological macromolecules and small molecules, but also provide valuable data of simulating the mechanism of riboflavin in biological systems and understanding of the relationship between structure and function of hemoglobin.更多还原