吡啶酰胺与DNA作用的光谱法研究

应用紫外光谱，荧光光谱以及表面增强拉曼光谱研究了3类吡啶酰胺化合物：N,N’-双(2-吡啶甲酰胺)-1,2-乙烷（H₂L1），N,N’-双(2-吡啶甲酰胺)-1,2-苯（H₂L2），N-苯基-吡啶-2-甲酰胺（HL3）与DNA的作用方式和作用强度。紫外光谱研究得到H₂L1，H₂L2和HL3与DNA的结合常数K_b分别为1.20×104 ，1.33×104, 1.52×104。随着化合物浓度的增大，EB-DNA复合物体系的荧光强度逐步减弱，H₂L1 , H₂L2和HL3的线性Stern-Volmer常数K_SV分别为0.67, 1.52, 1.73。可见HL3与DNA的结合能力略大于其他2个，表明其具有较小的空间位阻和合适的平面结构将更有利于与DNA的作用。随着DNA的加入，H₂L的拉曼谱带强度均表现为显著的减弱且有略微的红移现象。琼脂糖凝胶电泳分析表明，3类吡啶酰胺都能对pBR322DNA进行一定程度的切割，随着其浓度的增加，开环构型DNA逐渐增多，而超螺旋构型DNA逐渐减少，但电泳图上均没有出现线带，说明吡啶酰胺对DNA的切割没有选择性。

Synthesis and DNA-Binding Properties of Three Compouds Containing Pyridinecarboxamide

N,N’-bis(2-pyridinecarboxamide)-1,2-ethane(H₂L1), N, N’-bis(2-pyridinecarboxamide)-1,2-beneze(H₂L2) and N-phenylpyridine-2-carboxamide(HL3) were synthesized, and characterized by elemental analysis, IR and HNMR spectra. UV-visible (UV-Vis) spectra, fluorescence spectra and SERS spectra to study the interaction of the three ligands with calf thymus DNA. UV-visible (UV-Vis) spectra show that with the incremental addition of DNA, the bands of H₂L1, H₂L2 and HL3 all show Hypochromism. Meanwhile fluorescence spectra show that the addition of the three ligands to DNA pretreated with EB causes an appreciable reduction in fluorescence intensity，indicating that the ligands compete with ethidium bromide in binding to DNA, and free ethidium bromide increases. The addition of DNA causes the SERS signals of the ligands to weakened and some bands to disappeared. Based on the above experimental results, we conclude that the three ligands bind to DNA mainly through the intercalation mode. The binding constant of the three compouds K_b was calculated, 1.20×104 for H₂L1, 1.33×104 for H₂L2 and is 1.52×104 for HL3. K_r was also calculated to be 0.67, 1.52 and 1.73 for H₂L1, H₂L2 and HL3, respectively. The value indicates that the binding of HL3 to DNA is stronger than that of H₂L1 and H₂L2, as HL3 has proper planar structure, smaller molecular volume and less steric hindrance. The three ligands can all induce the cleavage of plasmid pBR322 DNA. An increase in H₂L1, H₂L2 and HL3 concentrations causes more transformation of plasmid DNA from closed circular conformations to nicked conformations. But linear conformations have not been observed. The cleavage of plasmid pBR322 DNA caused by the three ligands is not selective.