Direct observation of the multistep helix formation of poly-L-glutamic acids
Direct observation of the multistep helix formation of poly-L-glutamic acids
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DOI：
10.1021/ja026639f
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发表时间：
2002-10-02
影响因子：
15
通讯作者：
Morishima, I
中科院分区：
文献类型：
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作者：
Kimura, T;Takahashi, S;Morishima, I
用傅里叶变换红外光谱（FTIR）和圆二色谱（CD）研究了聚谷氨酸（PGA）的螺旋形成动力学。在pH（或FTIR的pD）8.0下，通过使用混合死时间为50 μs的快速溶液混合器将pH跳至4.9来引发34-残基PGA从无规卷曲形成螺旋。时间分辨FTIR光谱中酰胺I'线显示总螺旋含量快速增加（<100 μs）。同一过程的时间分辨CD谱也显示短螺旋片段（5 ± 1个残基）的快速（<150 μs）形成，随后短螺旋向长螺旋（>10个残基）的缓慢（<1 ms）延伸。类似的动力学观察到相同的pH值的跳跃的190个残基的PGA，虽然有额外的步骤，使螺旋形成的190个残基的PGA更复杂。所观察到的多步螺旋形成可能是由PGA的质子化侧链之间的强氢键相互作用引起的。
The helix formation dynamics of poly-l-glutamic acids (PGAs) were observed by the microsecond-resolved Fourier transform infrared (FTIR) and circular dichroism (CD) spectroscopies. The helix formation of 34-residue PGA from random coil at pH (or pD for FTIR) 8.0 was initiated by a pH jump to 4.9 using the rapid solution mixer whose mixing dead time is 50 μs. The amide I‘ line in the time-resolved FTIR spectra exhibited the fast (<100 μs) increase of the total helical content. The time-resolved CD spectra of the same process also showed the fast (<150 μs) formation of short helical segments (5 ± 1 residues), which was followed by the slower (<1 ms) elongation of the short helices to longer helices (>10 residues). Similar dynamics were observed for the same pH jump of ∼190-residue PGA, although there were additional steps that made the helix formation of ∼190-residue PGA more complex. The observed multistep helix formation is likely caused by the strong hydrogen-bonding interactions between the protonated side chains of PGAs.