Hartmann B, Pilet J, Ptak M, Ramstein J, Malfoy B, Leng M
Nucleic Acids Res. 1982 May 25;10(10):3261-77. doi: 10.1093/nar/10.10.3261.
The study of poly(dI-br5dC).poly(dI-br5dC) films by infrared spectroscopy shows that in low salt concentration, the conformation of this polynucleotide belongs to the B-family and in high salt concentration to the Z-family. 31P nuclear magnetic resonance and circular dichroism confirm the existence of these two forms. By circular dichroism and ultraviolet absorption, it is shown that the equilibrium constant of the B reversible Z transition depends upon temperature. The deuteration rates of exchangeable protons involved in hydrogen bonds between base pairs were deduced from the changes in absorbance near 1700 cm-1. In the B-form, one class of protons is measured with an exchange half-time of 20 minutes. In the Z-form, two classes of protons are measured with very different exchange half-times, the exchange half-time of the slow protons being of the order of 850 minutes. By comparison of these results with those previously obtained for poly(dG-dC).poly(dG-dC), these very slow protons of these two Z-polynucleotides are identified as the cytosine amino protons. A quantitative description of the dynamic structure of the Z-form is presented.
通过红外光谱对聚（dI-br5dC）·聚（dI-br5dC）薄膜的研究表明，在低盐浓度下，这种多核苷酸的构象属于B型，而在高盐浓度下则属于Z型。31P核磁共振和圆二色性证实了这两种形式的存在。通过圆二色性和紫外吸收表明，B可逆Z转变的平衡常数取决于温度。从1700 cm-1附近吸光度的变化推导出参与碱基对间氢键的可交换质子的氘化率。在B型中，一类质子的交换半衰期为20分钟。在Z型中，两类质子的交换半衰期差异很大，慢质子的交换半衰期约为850分钟。通过将这些结果与先前对聚（dG-dC）·聚（dG-dC）获得的结果进行比较，这两种Z多核苷酸的这些非常慢的质子被确定为胞嘧啶氨基质子。给出了Z型动态结构的定量描述。
