变温拉曼光谱和DSC探讨人参皂苷Rb1分子与DPPC双层膜的作用

Study on the Effects of Ginsenoside Rb1 on DPPC Bilayers by Using Thermo-Raman Spectrum and DSC

研究人参皂苷分子与生物膜的作用对于深入了解中药人参的药理活性及其生物学功效至关重要。DPPC作为具有双分子层结构的脂质分子,常被许多国内外学者作为模拟膜的模型来研究药物分子与细胞膜的作用;Rb1作为中药人参中的重要皂苷成分,具有显著的药理学功效和生物性能。拉曼光谱是探讨分子间作用的有力工具,差示扫描量热技术(differential scanning calorimetry,DSC)是研究脂双层分子单体及其与药物分子作用的常用技术,而将两者结合研究药物分子对细胞膜作用的研究的报道较少。本文采用变温拉曼光谱和DSC探讨了在温度变化条件下人参皂苷Rb1单体分子与DPPC双层膜的作用。通过拉曼光谱测试,在Rb1作用前后,DPPC分子极性头部O—C—C—N+和C—C伸缩振动区域以及烷基链部分C—H键的伸缩振动区域的变化表明,随着温度的增加,含有一定浓度Rb1的DPPC磷脂极性头部旁氏构象没有发生变化,脂酰链的无序性构象增多,侧向排列的无序性增强,DPPC脂双层的流动性增加。由DSC实验得到的几个热力学常数[相变温度(Tm)、半峰宽(ΔT1/2)及相转变焓值(ΔH)]的变化表明,DSC进一步验证了变温拉曼实验结果,随着Rb1浓度的增大,DPPC双层膜的相变温度显著下降,流动性增强,说明Rb1对DPPC双层膜的影响较大。

The research on the interactions between Ginsenosides and biomembranes plays a crucial role in thorough understanding the pharmacological activity and biologyical effect of Chinese medicine Panax ginseng.With the bilayer structure,DPPC often serves as an simulation model of the cell membrane to study the role of drug molecules and cell membranes.Ginsenoside Rb1,one of the most important components of Panaxginseng,playing the significant roles of pharmacological effects and biological properties.Raman and differential scanning calorimetry（DSC）are respectively apowerful tool for discussing the molecular interaction,and a kind of general technology by which researching the bilayer monomer structures and its interactions with drug molecules.However,rarely research reports on the interactions between drug molecules and biomembranes by means of both technologies above.In this paper,the influence of ginsenoside monomer Rb1 on DPPC membrane bilayers was investigated by thermo-Raman and DSC.In Raman spectra,the changes of DPPC molecule have been observed before and after interacted with ginsenoside Rb1,the data analysis indicates three aspects：the O—C—C—N^＋ polar head group skeleton,C—C stretching vibration area,and the C—H bond stretching vibrarion in terminated methyl group of alkyl chains.The results showed that ginsenoside Rb1 molecule with certain concentration has not changed the gauche conformation of the polar head backbone group in DPPC bilayers,the order of the internal molecular chain and the lateral chain-chain packing have been decreased as the temperature increased,the lateral disposed disorder has been increased.The changes of some thermodynamic constants obtained by DSC experiment such as phase transition temperature（Tm）、the temperature at which the transition is half completed（ΔT1/2）,and the transition enthalpy normalized per mol of DPPC（ΔH）have been showed further results of the thermo Raman experiments,with increasing the concentration of ginsenoside Rb1,the pre-transition temperature of DPPC bilayers dropped immediately with small amount of the Rb1 drug when the containtion was only 5 mol% and the whole system has been destructed at the same time,the main phase transition peak showed as a new little shoulder seam,however,both pre-and main transition peak disappeared completely until the drug concentration increased to 20mol%,the phase transition temperature of DPPC has been reduced significantly,and the fluidity of bilayers has been increased.Both experiments indicated that the strong effects of ginsenoside Rb1 on DPPC.