Photophysical And Photochemical Properties Of The Bola Surfactant (g <sub> 2 </ Sub> D) And Riboflavin In The Compound System

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.