Conformation transition kinetics of regenerated Bombyx mori silk fibroin membrane monitored by time-resolved FTIR spectroscopy
Conformation transition kinetics of regenerated Bombyx mori silk fibroin membrane monitored by time-resolved FTIR spectroscopy
复制标题
时间分辨傅立叶变换红外光谱监测再生家蚕丝素蛋白膜的构象转变动力学
DOI：
10.1016/s0301-4622(00)00213-1
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发表时间：
2001-01-31
影响因子：
3.8
通讯作者：
Chance, MR
中科院分区：
文献类型：
--
作者：
Chen, X;Shao, ZZ;Chance, MR
首次用时间分辨傅里叶变换红外光谱(FTIR)监测了乙醇诱导的家蚕再生丝素膜从模糊到有序的构象转变。从傅里叶变换红外差谱分析可知，乙醇加入后的时间尺度最短为6 S，最长为1h。观察到1618 cm(-1)处增加的带的强度随时间的曲线图，表明形成了与1668 cm(-1)处的带的强度损失相一致的β-折叠，表明随机卷曲和/或丝素I结构减少。这两个红外标记物都符合相同的双相指数衰减函数，然而，在观察到的转变开始之前，有一个明显的爆发阶段。构象转变过程表明，要么(至少)通过包含不同水平的β-折叠结构的两个中间状态顺序进行，要么具有平行的初始β-折叠形成路径，随后是较慢的“完美”阶段。第一个观察到的过程在混合后几秒(甚至更快)，在6 S收集第一个光谱之前，在爆发阶段形成。第二个观察到的过程发生的时间常数类似于0.5min，然后在这个阶段存在的中间过程以5.5min的时间常数继续，完成了观察到的β-片层的形成。这种较慢的中间体的构象转变不仅可以通过对上面讨论的无规卷曲和β-折叠特定带的动力学分析来指示。它大致与1695 cm(-1)处另一个红外标记的出现相吻合，这可能是完美结构形成所特有的p-折叠结构的标记。通过红外光谱分析这种蛋白质的构象转变，为了解家蚕茧形成过程中令人着迷的部分提供了线索。(C)2001 Elsevier Science B.V.保留所有权利。
The ethanol-induced conformation transition of regenerated Bombyx mori silk fibroin membrane from a poorly defined to the well ordered state was monitored by time-resolved Fourier transform infrared spectroscopy (FTIR) for the first time. From the analysis of FTIR difference spectra, taken on time scales as short as 6 s and up to 1 h after addition of ethanol. intensity vs. time plots of an increasing band at 1618 cm(-1) were observed indicating formation of a beta -sheet coincident with the loss of intensity of a band at 1668 cm(-1) indicating decreases of random coil and/or silk I structure. Both infrared markers were fitted with identical biphasic exponential decay functions, however, there was a clear burst phase occurring prior to the onset of the observed transitions. The conformation transition process is indicated to either proceed sequentially through (at least) two intermediate states that contain different levels of beta -sheet structure or to have parallel pathways of initial beta -sheet formation followed by a slower 'perfection' phase. The first observed process forms in a burst phase a few seconds after mixing (or even faster), prior to the collection of the first spectrum at 6 s. The second observed process occurs with a time constant of similar to 0.5 min, the intermediate present at this stage then continues with a time constant of 5.5 min completing the observed formation of the beta -sheet. The conformation transition of this slower intermediate is not only indicated by an analysis of the kinetics of the random coil and beta -sheet-specific bands discussed above. it roughly coincides with the appearance of an additional infrared marker at 1695 cm(-1), which may be a marker for p-sheet structure specific to the formation of the perfected structure. The conformation transition of this protein analyzed by infrared spectroscopy provides insight into a part of the fascinating process of cocoon formation in B. mori. (C) 2001 Elsevier Science B.V. All rights reserved.