摘要
The preparations,the formation conditions and stabilities of duplex dA_(10)·dT_(10)and triplax dA_(10)·2dT_(10),and the interactions of ethidium bromide with them in an appropriate buffer are reported.Flu- orescence spectra show that ethidium can be used as a useful fluorescence probe to detect triplex formation, and its fluorescence is significantly increased by either the duplex or triplex,but less in the case of the triplex.Thermal denaturation profiles demonstrate that the stability of the triplex is enhanced by ethidium. Fluorescence energy transfer studies suggest the existence of similar energy transfer from the triplex or du- plex to the bound ethidium but the presence of the triplex results in substantially smaller energy transfer than that of the duplex does.Furthermore,fluorescence quenching using the anionic quencher[Fe(CN)_6]^(4-)can- not decrease the fluorescence intensities of triplex/ethidium complex.These results demonstrate that ethidi- um has significantly binding affinity with the triplex,and interacts with it via intercalative mechanism,thus increases its stability.
The preparations,the formation conditions and stabilities of duplex dA<sub>10</sub>·dT<sub>10</sub>and triplaxdA<sub>10</sub>·2dT<sub>10</sub>,and the interactions of ethidium bromide with them in an appropriate buffer are reported.Flu-orescence spectra show that ethidium can be used as a useful fluorescence probe to detect triplex formation,and its fluorescence is significantly increased by either the duplex or triplex,but less in the case of thetriplex.Thermal denaturation profiles demonstrate that the stability of the triplex is enhanced by ethidium.Fluorescence energy transfer studies suggest the existence of similar energy transfer from the triplex or du-plex to the bound ethidium but the presence of the triplex results in substantially smaller energy transfer thanthat of the duplex does.Furthermore,fluorescence quenching using the anionic quencher[Fe（CN）<sub>6</sub>]<sup>4-</sup>can-not decrease the fluorescence intensities of triplex/ethidium complex.These results demonstrate that ethidi-um has significantly binding affinity with the triplex,and interacts with it via intercalative mechanism,thusincreases its stability.
基金
the Eighth Five-Year Plan's Key Basic Research Project of Academia Sinica
