Pilet J, Leng M
Proc Natl Acad Sci U S A. 1982 Jan;79(1):26-30. doi: 10.1073/pnas.79.1.26.
The structures of B and Z forms of poly(dG-dC).poly(dG-dC) in oriented hydrated films have been investigated by infrared spectroscopy. First, the infrared linear dichroism spectrum of poly(dG-dC).poly(dG-dC) in B form (high relative humidity and 2 M Na+) was recorded. The spectrum of the Z form was recorded at a lower relative humidity and higher sodium content (4 M). The experimental conditions were similar to those used in x-ray diffraction studies of left-handed poly(dG-dC).poly(dG-dC) fibers. A qualitative agreement was found between the calculated values of the angles characteristic of the orientation of PO-2 groups with respect to the helical axis in the ZI form and the experimental values. The infrared spectra of B and Z form and the experimental values. The infrared spectra of B and Z forms show some significant differences in H2O and 2H2O. The deuteration rates of exchangeable protons involved in hydrogen bonds between guanine and cytosine residues were deduced from the changes in absorbance near 1700 cm-1. In the B form, the exchange half-time is of the order of 20 min. In the Z form, the exchange half-time of some protons is very slow, of the order of 24 hr. Because of the similarity between these values and those previously reported for the high-salt and low-salt form of poly(dG-dC).poly(dG-dC) in solution, we conclude that the high-salt form of poly(dG-dC).poly(dG-dC) in solution belongs to the Z family.
通过红外光谱研究了取向水合膜中聚（dG-dC）·聚（dG-dC）的B型和Z型结构。首先，记录了聚（dG-dC）·聚（dG-dC）在B型（高相对湿度和2M Na+）下的红外线性二色性光谱。Z型光谱是在较低相对湿度和较高钠含量（4M）下记录的。实验条件与用于左手螺旋聚（dG-dC）·聚（dG-dC）纤维的X射线衍射研究中使用的条件相似。在ZI型中，PO-2基团相对于螺旋轴的取向特征角的计算值与实验值之间发现了定性一致性。B型和Z型的红外光谱以及实验值。B型和Z型的红外光谱在H2O和2H2O中显示出一些显著差异。从1700cm-1附近吸光度的变化推导出鸟嘌呤和胞嘧啶残基之间氢键中可交换质子的氘代率。在B型中，交换半衰期约为20分钟。在Z型中，一些质子的交换半衰期非常慢，约为24小时。由于这些值与先前报道的溶液中聚（dG-dC）·聚（dG-dC）的高盐和低盐形式的值相似，我们得出结论，溶液中聚（dG-dC）·聚（dG-dC）的高盐形式属于Z家族。
