Infrared Reflection-Absorption Spectroscopy and Polarization-Modulated Infrared Reflection-Absorption Spectroscopy Studies of the Organophosphorus Acid Anhydrolase Langmuir Monolayer
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- 作者：Chengshan Wang ; Jiayin Zheng ; Liang Zhao ; Vipin K. Rastogi ; Saumil S. Shah ; Joseph J. DeFrank ; Roger M. Leblanc
- 刊名：Journal of Physical Chemistry B
- 出版年：2008
- 出版时间：April 24, 2008
- 年：2008
- 卷：112
- 期：16
- 页码：5250 - 5256
- 全文大小：193K
- 年卷期：v.112,no.16(April 24, 2008)
- ISSN：1520-5207
文摘
The secondary structure of the organophosphorus acid anhydrolase (OPAA) Langmuir monolayer in the absenceand presence of diisopropylfluorophosphate (DFP) in the subphase was studied by infrared reflection-absorption spectroscopy (IRRAS) and polarization-modulated IRRAS (PM-IRRAS). The results of both theIRRAS and the PM-IRRAS indicated that the 
-helix and the 
-sheet conformations in OPAA were parallelto the air-water interface at a surface pressure of 0 mN·m-1 in the absence of DFP in the subphase. Whenthe surface pressure increased, the -helix and the -sheet conformations became tilted. When DFP wasadded to the subphase at a concentration of 1.1 × 10-5 M, the -helix conformation of OPAA was stillparallel to the air-water interface, whereas the -sheet conformation was perpendicular at 0 mN·m-1. Theorientations of both the -helix and the -sheet conformations did not change with the increase of surfacepressure. The shape of OPAA molecules is supposed to be elliptic, and the long axis of OPAA was parallelto the air-water interface in the absence of DFP in the subphase, whereas the long axis became perpendicularin the presence of DFP. This result explains the decrease of the limiting molecular area of the OPAA Langmuirmonolayer when DFP was dissolved in the subphase.
-helix and the -sheet conformations in OPAA were parallelto the air-water interface at a surface pressure of 0 mN·m-1 in the absence of DFP in the subphase. Whenthe surface pressure increased, the -helix and the -sheet conformations became tilted. When DFP wasadded to the subphase at a concentration of 1.1 × 10-5 M, the -helix conformation of OPAA was stillparallel to the air-water interface, whereas the -sheet conformation was perpendicular at 0 mN·m-1. Theorientations of both the -helix and the -sheet conformations did not change with the increase of surfacepressure. The shape of OPAA molecules is supposed to be elliptic, and the long axis of OPAA was parallelto the air-water interface in the absence of DFP in the subphase, whereas the long axis became perpendicularin the presence of DFP. This result explains the decrease of the limiting molecular area of the OPAA Langmuirmonolayer when DFP was dissolved in the subphase.