不同波段的紫外辐射对DNA构象影响的拉曼光谱研究

Raman Spectroscopic Study of the Effect of Ultraviolet Radiation on DNA Configuration in Aqueous Solutions

研究了小牛胸腺DNA水溶液经不同时间不同波段紫外辐射后的拉曼光谱。结果表明 :仅仅经过9min强度为18.68W/m2的全波段紫外辐射 ,DNA就遭到了严重损伤。表征PO2-对称伸张振动的1094cm -1谱线分裂成4条谱线 ,说明DNA构象遭到破坏 ,构型发生了变化。UV_A &UV_B波段的紫外辐射对DNA的影响比全波段的紫外辐射对DNA的影响小得多 ,但经过较长时间辐射后 ,仍对DNA构型构象产生了影响 ,即A型构象增强 ,B型构象减弱。经过2h的UV_A辐射 ,出现了表征A型构象的805cm -1和816cm -1谱线 ,且816cm -1峰与未经辐射的表征A型的803cm-1峰相比 ,强度大得多。经过16h的UV_A辐射后 ,805cm-1 谱线消失 ,816cm-1 谱线移到了813cm-1,且强度减弱50%,表明水溶液中的DNA在UV_A照射中A型构象不稳定 。

The Raman spectra of calf thymus DNAin aqueous solutions were studied after irradiation for differˉent durations with UVlight of different wavelength bands.After irradiation with the whole-band UV light of an intensity of18.68W/m 2 for merely9min,DNA was seriously damaged.The peak at1094cm -1 characˉterizing the symmetric stretching vibration of PO 2- was splitted into four weaker peaks.It implies a change in molecular configuration.The configuration change in the DNA molecule induced by UV-A and UV-B radiaˉtion is far less than that induced by the whole-band UV radiation.Upon prolonged irradiation with UV-A and UV - B,the Raman spectra of the A-DNA formbecame stronger,whereas those of the B-DNA form beˉcame weaker.The peaks at805cm -1 and816cm -1 corresponding to the A-DNA form emerged after2-hour UV-A irradiation.The peak at816cm -1 became much more intensive than the peak at803cm -1 before irradiation.However,after16h UV-A irradiation the peak at803cm -1 vanished.Meanwhile,the peak at816cm -1 shifted to813cm -1 ,and its intensity was reduced to only50%of the original.These observations indicated the A-DNA form upon UV-A irradiation is not stable and apt to changes in aqueous solutions.