水溶液中的环状DNA超螺旋空间构象

质粒DNA水溶液的喇曼光谱研究表明,854和1-083-cm-1特征峰反映了DNA主链骨架三级结构的振动状态;表征脱氧核糖中C-C伸缩振动的969-cm-1峰,其相对强度值介于线性DNA在水溶液和在纤维状态下所得数值之间(0.46＜0.83＜1.10);DNA中胸腺嘧啶的堆积反应活性增加,A-T间氢键能减弱.这些参数是辨认环状DNA分子三级结构的有效依据.

Superhelical Spatial Conformation on Circular DNA in Aqueous Solution

The circular DNA has been shown a regular superhelical spatial conformation.The Raman spectra of bacterial plasmid DNA in aqueous solution were recorded.Both diagnostic bands at the 854 and 1?083?cm -1 reflecting the vibration state of the tertiary structure of the DNA main backbone are usually hard to find in the Raman spectra of the linear DNA molecule and their assignments have been discussed.The intensity of the peak at 969?cm -1 ,corresponding to the C'-C' stretching vibration of the deoxyribose,is between that of calf thymus DNA in aqueous solution and in fiber (0.46<0.83<1.10).As a result of analyzing base stacking,the existence of the superhelical spatial conformation represents both the increases in the staking reaction activity of thymine residues in the DNA molecule and the damage of a considerable amount of the Watson Crick type hydrogen bonding in the AT base pairs.Meanwhile,the characteristic band at 1?378?cm -1 ,corresponding to C-N and C=O group vibration,indicating the composition of H bond of the thymine,has markedly Raman hypochromism.It is a sufficient basis of confirming the tertiary structure of circular DNA molecule with Raman characteristic bands.