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首页> 外文期刊>The journal of physical chemistry, B. Condensed matter, materials, surfaces, interfaces & biophysical >Reexamination of Ultrasonic Relaxation Kinetics of Aqueous Solutions of Nucleotides: Evidence for Fast Syn-Anti Glycosyl Isomerization in Adenosine 5'-Monophosphate and Adenosine 5'-Diphosphate
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Reexamination of Ultrasonic Relaxation Kinetics of Aqueous Solutions of Nucleotides: Evidence for Fast Syn-Anti Glycosyl Isomerization in Adenosine 5'-Monophosphate and Adenosine 5'-Diphosphate

机译：核苷酸水溶液的超声松弛动力学的重新检查：腺苷5'-单磷酸酯和腺苷5'-二磷酸酯的快速合成抗糖基异构化的证据

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摘要

Ultrasonic absorption coefficients in aqueous solutions of adenosine 5'-monophosphate and adenosine 5'-diphosphate were measured at 25℃as a function of the concentration and pH in the frequency range from 0.8 to 220 MHz. At pH near 5, there existed two relaxational absorptions. One is observed at the frequency range < 10 MHz with a large amplitude of the ultrasonic relaxation and a relaxation frequency which is strongly dependent on both the nucleotide concentration and pH. The source of the relaxation was attributed to a perturbation of the chemical equilibrium associated with the proton transfer reaction: N↓(1)-R-PO↑(2-)↓(4) + ↑(+)HN↓(1)-R-PO↓(4)H↓(-)# ↑(2)N↓(1)-R-PO↓(4)H↑(-). The forward and reverse rate constants were determined from the concentration dependence of the reactants and the solution pH. The forward rate constant obtained was similar to that previously reported. When the solution pH was increased to > 11, the relaxation associated with the proton transfer reaction disappeared. A second relaxation is found at around 100 MHz, and its amplitude is smaller than that due to the proton transfer reaction. This relaxation is barely observed at neutral pH, but it is clearly distinguishable at high pH because the absorption associated with the proton transfer reaction is no longer observable. The relaxation frequency of the second relaxation is independent of nucleotide concentration and the solution pH, and the maximum absorption per wavelength increases linearly with concentration. It was concluded that the source of this relaxation is an isomerization process, probably the syn-anti interconversion of nucleotides. The value of the relaxation frequency in aqueous solutions of ADP was greater than that in AMP solutions, which in turn is greater than that for adenosine. The results are discussed in relation to nucleotide molecular structures and interactions.
机译：在25℃下，在0.8至220 MHz频率范围内，测定5'-单磷酸腺苷和5'-二磷酸腺苷在水溶液中的超声吸收系数，作为浓度和pH的函数。 pH值接近5时，存在两个弛豫吸收。在＜10MHz的频率范围内观察到一个，其具有大的超声弛豫幅度和强烈依赖于核苷酸浓度和pH的弛豫频率。弛豫的来源归因于与质子转移反应有关的化学平衡的扰动：N↓（1）-R-PO↑（2-）↓（4）+↑（+）HN↓（1）- R-PO↓（4）H↓（-）＃↑（2）N↓（1）-R-PO↓（4）H↑（-）。从反应物的浓度依赖性和溶液pH确定正向和反向速率常数。获得的前进速率常数与先前报道的相似。当溶液的pH值增加到> 11时，与质子转移反应相关的弛豫消失了。在约100 MHz处发现第二次弛豫，其幅度小于质子转移反应引起的幅度。在中性pH下几乎没有观察到这种松弛，但是在高pH下却明显可分辨，因为不再观察到与质子转移反应有关的吸收。第二次弛豫的弛豫频率与核苷酸浓度和溶液pH无关，并且每个波长的最大吸收随浓度线性增加。结论是这种松弛的来源是异构化过程，可能是核苷酸的顺反互变。 ADP水溶液中的弛豫频率值大于AMP溶液中的弛豫频率，而AMP溶液中的弛豫频率又大于腺苷。讨论了有关核苷酸分子结构和相互作用的结果。

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