Secondary structure of organophosphorus hydrolase in solution and in Langmuir-Blodgett film studied by circular dichroism spectroscopy
Secondary structure of organophosphorus hydrolase in solution and in Langmuir-Blodgett film studied by circular dichroism spectroscopy
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DOI：
10.1021/jp0477396
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发表时间：
2004-11-04
影响因子：
3.3
通讯作者：
Leblanc, RM
中科院分区：
文献类型：
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作者：
Zheng, JY;Constantine, CA;Leblanc, RM
用远紫外圆二色光谱（CD）研究了有机磷水解酶（OPH）的二级结构。考察了pH值在3.56 ~ 9.60范围内对OPH溶液二级结构的影响。CD光谱显示，当pH值接近等电点（7.6）时，OPH的二级结构清晰；然而，当pH值进一步增加或降低时，它就会被破坏。这可以用螺旋结构的丧失来解释。pH对CD光谱的影响有助于阐明在空气-水界面获得稳定的OPH Langmuir膜所需的最佳pH值及其与酶的二级结构的关系。通过对OPH在溶液、Langmuir-Blodgett膜和干膜中二级结构的热处理对比研究表明，分子排列对OPH的热稳定性起主导作用。利用CDPro软件包对OPH溶液的CD光谱进行了二级结构的定量估计。结果表明，随着pH和温度的变化，a-螺旋链的百分比降低，β -链的百分比增加。
The secondary structure of organophosphorus hydrolase (OPH) has been studied with circular dichroism (CD) spectroscopy in the far-UV region. The effect of pH on the secondary structure of OPH solution was examined over the pH range from 3.56 to 9.60. As shown on the CD spectra, the secondary structure of OPH is well defined when the pH value is near the isoelectric point (7.6); however, it is destroyed when the pH values are increased or decreased further. This is explained by the loss of helical structure. The pH effect on CD spectra contributes to clarify the optimum pH needed to obtain a stable OPH Langmuir film at the air-water interface and its correlation to the secondary structure of the enzyme. Comparative study of the thermal treatment on the secondary structure of OPH in solution, Langmuir-Blodgett film, and dry film shows that the molecular arrangement plays a dominant role in the thermal stability of OPH. With use of the CDPro software package a quantitative estimation of the secondary structure from the CD spectra of OPH solution was obtained. Results show that there is a decrease in the percentage of the a-helical and an increase of beta-strands with the change of pH or temperature.