Direct Observation of the Multistep Helix Formation of Poly-L-glutamic Acids
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- 作者：Tetsunari Kimura ; Satoshi Takahashi ; Shuji Akiyama ; Takanori Uzawa ; Koichiro Ishimori ; and Isao Morishima
- 刊名：Journal of the American Chemical Society
- 出版年：2002
- 出版时间：October 2, 2002
- 年：2002
- 卷：124
- 期：39
- 页码：11596 - 11597
- 全文大小：48K
- 年卷期：v.124,no.39(October 2, 2002)
- ISSN：1520-5126
文摘
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 
s. The amide I' line in the time-resolved FTIR spectra exhibited the fast (<100 s) increase of the total helical content. The time-resolved CD spectra of the same process also showed the fast (<150 s) 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.
s. The amide I' line in the time-resolved FTIR spectra exhibited the fast (<100 s) increase of the total helical content. The time-resolved CD spectra of the same process also showed the fast (<150 s) 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.