STRUCTURAL STUDIES OF RIBONUCLEASE .5. REVERSIBLE CHANGE OF CONFIGURATION
STRUCTURAL STUDIES OF RIBONUCLEASE .5. REVERSIBLE CHANGE OF CONFIGURATION
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DOI：
10.1021/ja01476a025
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发表时间：
1961-01-01
影响因子：
15
通讯作者：
SCHERAGA, HA
中科院分区：
文献类型：
--
作者：
HERMANS, J;SCHERAGA, HA
采用紫外差谱法和旋光度法研究了核糖核酸酶构型随pH和温度变化的可逆变化。- [a]的增加（表明螺旋含量的损失）和紫外线吸收光谱的“蓝移”（表明酪氨酸基环境的变化）在变性过程中相互平行。得到了构型变化的平衡数据。这些包括：Tu和AFobad的ph依赖性。，以及AH3obsd的值。（等于51千卡/摩尔以下，与pH无关）。在Ttr之上，是AflAbsd。增加，表明不止一种变性形式参与了TXr以上的平衡。提出了一种理论来解释Txt和AFohsd的/ b> h依赖性。在局部相互作用和一般静电效应方面，基于四种不同的可能模型。将这一理论应用于高达1摄氏度的温度下，有可能排除其中两个模型。区分其他两种模型是不可能的。结果表明，天然分子含有一个（或可能两个）pKH为2.5的羧基。变性后内在pK变为正常（4.6），这一基团（或多个基团）对ta和AF0hed的ph依赖性做出了重要贡献。fr变性。最后，举例说明核糖核酸酶的结构在决定其对各种试剂的反应性方面的重要性。
The reversible change of configuration in ribonuclease with varying pH and temperature was studied with ultraviolet difference spectra and optical rotation measurements. The increase in—[a](indicating loss of helical content) and the “blue shift” of the ultraviolet absorptionspectrum (indicating changes in the environment of the tyrosyl groups) parallel each other in the denaturation. Equilibrium data were obtained for the configurational change. These include: the pH-dependence of Tu and AFobad., and the value of AH3obsd.(equal to 51 kcal./mole below\, and independent of pH). Above Ttr, AflAbsd. increases, suggesting that more than one denatured form participates in the equilibrium above TXr. A theory was developed to account for the/> H-dependence of Txt and AFohsd. in terms of local interactions and general elec-trostatic effects, based on four different possiblemodels. Applying the theory at temperatures up to Tt „it was possible to rule out two of the models. Adistinction between the other two models was not possible. As a result, it is concluded that the native molecule contains one (or possibly two) carboxyl groups with pKH of 2.5. Theintrinsic pK becomes normal (4.6) upon denaturation, this group (or groups) making an important contribution to the pH-dependence of TA-and AF0hed. fr denaturation. Finally, examples are cited to illustrate the importance of theconfiguration of ribonuclease in determining its reactivity toward various reagents.