表面增强拉曼光谱研究小檗碱与DNA的相互作用

用表面增强拉曼光谱研究了小檗碱（BER）与小牛胸腺DNA（ct DNA)的相互作用,并对重要谱峰进行了归属。在Ag胶体系中,小檗碱分子的拉曼信号增强显著,表明小檗碱阳离子键合到银胶粒子的表面。加入ct NA之后,小檗碱分子的大部分SERS带的强度进一步增加,而仅有少数几个带的信号强度趋于消失,可能是小檗碱分子的异喹啉部分键合到DNA的小沟槽,小檗碱与DNA的相互作用模式主要是通过静电力及疏水相互作用,吸收光谱表明,Ag胶体系的存在并未改变小檗碱分子与DNA的相互作用模式。

SERS Studies on the Interaction of Berberine With ct DNA

The interaction between berberine and ct DNA was investigated by using FT\|Surface Enhancement Raman Scattering(SERS) spectroscopy. The FT\|SERS spectra of berberine and its complex with DNA were recorded in the Ag sol and pH 7.20 Tris solution. Vibrational assignment of the SERS active modes was done on the basis of normal coordinate analysis. Some Raman bands of berberine are dramatically increased in intensity on the silver colloid. Results suggest that berberine ring system around the nitrogen positively charged center should assume the perpendicular or at least tilted stances with respect to the surface of Ag sol nanoparticle through the electrostatic interaction. When ct DNA is added into the berberine solution, much stronger SERS signal with a factor of 1.5 was obtained for the most of FT\|SERS bands of the molecule due to DNA binding; only a few bands approach to disappear in intensity. This result implies that there are two binding modes between berberine and double helix DNA. The shifts of some Raman band were also observed on the DNA binding. SERS experiments show that the isoquinolone moiety of berberine molecule may be accommodated in the minor groove of DNA helix. Grooving binding is very likely to be the dominant mode in the interaction of berberine with double helix DNA.