纳米银为基底的表面增强拉曼光谱研究香豆素与牛血清白蛋白的相互作用

Surface-Enhanced Raman Spectroscopy with Nanosilver as the Substrate to Study the Interaction Between Coumarin and Bovine Serum Albumin (BSA)

实验报道了香豆素的拉曼光谱以及在银纳米粒子基底上的表面增强拉曼光谱,并对其特征峰进行了归属,与固体香豆素的常规拉曼进行对比,发现香豆素的特征峰位置基本没变.实验优化了牛血清白蛋白(BSA)与银纳米粒子的体积混合比例,研究了香豆素与BSA相互作用的表面增强拉曼光谱.实验表明, BSA与银纳米粒子体积比为1∶3混合时, BSA的拉曼增强信号最佳.在低浓度下,银纳米粒子对香豆素及BSA都有明显的增强效果,其增强效果主要体现在银纳米粒子与香豆素苯环中的π电子、羰基中的氧原子以及BSA中含有孤电子的N原子、蛋白质中二硫键中的S原子发生吸附作用.加入BSA后,香豆素中525,675 cm,和1 327 cm^(-1)处的拉曼信号发生红移,但并未消失,说明香豆素的骨架振动因与牛血清白蛋白发生作用而受到影响;拉曼位移1 184,1 230,1 563 cm^(-1)处的拉曼峰信号明显减弱,这是由于加入BSA后,香豆素的C—O不对称伸缩振动以及C=O的伸缩振动造成的; 847,897,1 488 cm^(-1)拉曼峰消失,这是由于香豆素中芳环平面与BSA作用而导致的.与香豆素的表面增强拉曼光谱信号相比,香豆素与BSA复合物的表面增强拉曼光谱信号明显减弱,可能是BSA的α-螺旋结构被香豆素分子中的平面结构所插入,产生非共价键的π-π堆积的作用,使香豆素中芳环π电子密度发生变化,引起能量改变.以银纳米粒子为基底,利用表面增强拉曼光谱考察香豆素与BSA的相互作用,具有分析时间短、操作简单快速、原位无损检测等优点,为香豆素及其他增香剂与蛋白质相互作用的深入研究及其药理研究提供了参考.

The Raman spectrum of coumarin and the surface-enhanced Raman spectrum (SERS) on the silver nanoparticle substrate were reported and the characteristic peaks were assigned. A comparison of SERS with the normal Raman spectrum (NRS) of solid coumarin indicated that the position of the characteristic peak of coumarin was basically unchanged. The experiment optimized the volume mixing ratio of bovine serum albumin (BSA) and silver nanoparticles and studied the SERS of the interaction of coumarin with BSA. The results demonstrated that when the volume ratio of BSA to silver nanoparticles was 1∶3, the bovine serum albumin showed the strongest Raman enhancement signal. At low concentrations, silver nanoparticles had obvious enhancement effects on both bovine serum albumin and coumarin. The enhancement effect was mainly reflected in the adsorption of π electrons in silver benzene and coumarin benzene ring, oxygen atom in carbonyl group, N atom containing lone electron in BSA, and S atom in disulfide bond in protein. After the addition of BSA, the Raman signal at 525 cm^-1, 675 cm^-1, and 1 327 cm^-1 in coumarin was red-shifted but did not disappear, indicating that the skeletal vibration of coumarin was affected by the interaction with BSA. The Raman signals at Raman shifts of 1 184 cm^-1, 1 230 cm^-1, 1 327 cm^-1 and 1 563 cm^-1 were significantly weakened, due to the C-O asymmetric stretching vibration and C = O stretching vibration of coumarin after BSA addition. The 847 cm^-1, 897 cm^-1, and 1 488 cm^-1 Raman peaks disappeared due to the action of the aromatic ring plane and bovine serum albumin in the coumarin. Compared with the SERS signal of coumarin, the SERS signals of coumarin and bovine serum albumin complex were obviously weakened. The cause might be that the α-helical structure of BSA was inserted by the planar structure in the coumarin molecule, resulting in π of non-covalent bond. The π stacking action changed the π electron density of the aromatic ring in the coumarin, bringing about an energy change. In summery, in this study silver nanoparticles were used as the substrate to investigate the interaction between coumarin and BSA with the SERS technique. The method has the advantages of short analysis time, simple and rapid operation, and in situ nondestructive detection, and provides a reference for the in-depth study of the interaction of other flavoring agents with proteins and its pharmacological research.