Takenaka A, Takimoto M, Sasada Y
Biochim Biophys Acta. 1984 Feb 14;797(2):239-46. doi: 10.1016/0304-4165(84)90127-2.
The three-dimensional structure of 3-(adenin-9-yl)propionhistamide hydrochloride, as a model of interactions between the protonated imidazolyl group and adenine moiety, has been determined by X-ray crystallography. The crystal data are a = 10.314 (1), b = 7.854 (1), c = 20.780 (1) A, beta = 92.765 (4), Z = 4, Dm = 1.32 g X cm-3, space group P2(1)/n. The imidazolium group interacts with adenine moiety by stacking. A comparison with the related neutral derivatives leads to a hypothesis that adenine stacks with the protonated, but not with the neutral, imidazolyl group. Such a characteristic behaviour of the imidazolyl group depending on protonation was shown by ultraviolet and NMR spectroscopy, and by polarographic experiments in solution. We note that a role of the essential histidine in RNAase reaction is a switch between capture and ejection of the substrate, which depends upon proton uptake and its release, respectively.
作为质子化咪唑基与腺嘌呤部分之间相互作用的模型，盐酸3-(腺嘌呤-9-基)丙酰组氨酸的三维结构已通过X射线晶体学确定。晶体数据为：a = 10.314(1)，b = 7.854(1)，c = 20.780(1) Å，β = 92.765(4)，Z = 4，Dm = 1.32 g·cm⁻³，空间群P2(1)/n。咪唑鎓基团通过堆积与腺嘌呤部分相互作用。与相关中性衍生物的比较得出一个假设，即腺嘌呤与质子化的而非中性的咪唑基堆积。咪唑基的这种取决于质子化的特征行为通过紫外光谱、核磁共振光谱以及溶液中的极谱实验得以体现。我们注意到，在核糖核酸酶反应中，必需组氨酸的作用是在底物的捕获和释放之间进行切换，这分别取决于质子的摄取和释放。
