GUANIDINIUM CHLORIDE INDUCTION OF PARTIAL UNFOLDING IN AMIDE PROTON-EXCHANGE IN RNASE-A
GUANIDINIUM CHLORIDE INDUCTION OF PARTIAL UNFOLDING IN AMIDE PROTON-EXCHANGE IN RNASE-A
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DOI：
10.1126/science.8235609
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发表时间：
1993-11-05
期刊：
影响因子：
56.9
通讯作者：
BALDWIN, RL
中科院分区：
文献类型：
--
作者：
MAYO, SL;BALDWIN, RL
在pH* 5.5（未校正pH以D2O测量），34℃的条件下，在0.0 ~ 0.7 M的氯化胍（GdmCl）中，测量了23个核糖核酸酶A （RNase A）肽NH质子缓慢交换的酰胺（NH）质子交换率。目的是找出GdmCl是否通过与部分或全部未展开的交换中间体结合来诱导交换。据预测，当汇率的对数作为GdmCl的摩尔浓度的函数绘制时，斜率应该是交换中间体中暴露于GdmCl的埋藏表面积的度量。结果表明，这些浓度的GdmCl确实通过部分展开机制诱导了所有23个质子的交换；这意味着交换反应可以用来研究局部区域的展开和稳定性。在23个质子中，9个在较低浓度的GdmCl下也表现出第二种交换机制，这种机制几乎与GdmCl浓度无关，被称为“有限结构波动”。
Amide (NH) proton exchange rates were measured in 0.0 to 0.7 M guanidinium chloride (GdmCl) for 23 slowly exchanging peptide NH protons of ribonuclease A (RNase A) at pH* 5.5 (uncorrected pH measured in D2O), 34-degrees-C. The purpose was to find out whether GdmCl induces exchange through binding to exchange intermediates that are partly or wholly unfolded. It was predicted that, when the logarithm of the exchange rate is plotted as a function of the molarity of GdmCl, the slope should be a measure of the amount of buried surface area exposed to GdmCl in the exchange intermediate. The results indicate that these concentrations of GdmCl do induce exchange by means of a partial unfolding mechanism for all 23 protons; this implies that exchange reactions can be used to study the unfolding and stability of local regions. Of the 23 protons, nine also show a second mechanism of exchange at lower concentrations of GdmCl, a mechanism that is nearly independent of GdmCl concentration and is termed ''limited structural fluctuation.''