水溶性阳离子卟啉作为多功能DNA结合试剂在光动力学疗法、抗病毒药物等方面得到了越来越多的应用,因此研究阳离子卟啉与DNA的相互作用引起人们极大的兴趣。文章采用吸收光谱、荧光光谱和共振光散射技术研究了meso-四(4-三甲铵基苯基)卟啉(TMAP)和5-苯基-10,15,20-三(N-甲基-4-吡啶基)卟啉(TriMPyP)两种水溶性阳离子卟啉在水溶液中的聚集状态及与小牛胸腺DNA(ctDNA)的相互作用。在R>1时(R=cTMAP/cDNA),TMAP在DNA分子表面发生聚集,吸收光谱有明显的减色效应,卟啉的荧光被猝灭。在R<1时,TMAP与DNA以外部结合方式结合,荧光得到增强,共振光信号减弱。DNA的加入,使TriMPyP的聚集程度进一步增加。考察了离子强度对卟啉与DNA相互作用的影响,离子强度增大,卟啉的荧光得到增强,卟啉与DNA的结合方式发生改变。

Interest in the interaction between cationic porphyrins,particularly derivatives of meso-tetra(N-methylpyridinium-4-yl)porphyrin(TMPyP),and DNA abounds because they are versatile DNA-binding agents that could find application in photodynamic therapy,cancer detection,artificial nucleases,virus inhibition and so on.The interaction of two water-soluble cationic porphyrins,meso-tetrakis(4-N,N,N-trimethylanilinium)porphyrin (TMAP) and 5-phenyL^-10,15,20-tris[4-(N-methyl)pyridinium]porphyrin (TriMPyP),with calf thymus DNA (ctDNA) was studied by UV-Vis absorption spectroscopy,fluorescence spectroscopy and resonance light scattering technique.TriMPyP forms aggregate in water due to the molecular asymmetry while TMAP exists as monomers.At lower concentrations of ctDNA (R>1,R =cTMAP/cDNA base pair),the interaction of TMAP with DNA leads to significant hypochromicity and bathochromic shift of absorption spectra.And the fluorescence of TMAP was quenched while it showed enhanced resonance light scattering signals.But the extent of enhancement of resonance light scattering signals is very small,so the aggregate of TMAP is not very high.These observations indicate the self-stacking of TMAP along the DNA surface.At higher concentrations of ctDNA (R<1),TMAP association with DNA is via outside binding which is accompanied with hyperchromic effect and fluorescence enhancement while the resonance light scattering signals is reduced.DNA addition decreases the fluorescence intensity of TriMPyP and it shifts the peak to the higher wavelengths (red shift).The interaction with DNA promotes the aggregation of TriMPyP and no simple outside binding is observed even at higher concentrations of ctDNA.The steric effect of molecular distortion constrains the intercalation or further binding to DNA.The effect of ionic strength on the interaction was investigated at two DNA concentrations,1.2 and 24.0 μmol·L-1,for TMAP.The Interactions of both porphyrins with DNA show high sensitivity to ionic strength.By addition of NaCl,electrostatic attraction is decreased,resulting in the change of binding mode.