Ordered adsorption of coagulation factor XII on negatively charged polymer surfaces probed by sum frequency generation vibrational spectroscopy |
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Authors: | Xiaoyun Chen Jie Wang Zoltan Paszti Fulin Wang Joel N Schrauben Volodymyr V Tarabara Alvin H Schmaier Zhan Chen |
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Institution: | (1) Department of Chemistry, University of Michigan, Ann Arbor, MI 48109, USA;(2) Chemical Research Center of Hungarian Academy of Sciences, P.O. Box 17, 1525 Budapest, Hungary;(3) Department of Civil and Environmental Engineering, Michigan State University, East Lansing, MI 48824, USA;(4) Division of Hematology/Oncology, Case Western Reserve University, 10900 Euclid Avenue, WRB2-130, Cleveland, OH 44106, USA |
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Abstract: | Electrostatic interactions between negatively charged polymer surfaces and factor XII (FXII), a blood coagulation factor,
were investigated by sum frequency generation (SFG) vibrational spectroscopy, supplemented by several analytical techniques
including attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), quartz crystal microbalance (QCM),
ζ-potential measurement, and chromogenic assay. A series of sulfonated polystyrenes (sPS) with different sulfonation levels
were synthesized as model surfaces with different surface charge densities. SFG spectra collected from FXII adsorbed onto
PS and sPS surfaces with different surface charge densities showed remarkable differences in spectral features and especially
in spectral intensity. Chromogenic assay experiments showed that highly charged sPS surfaces induced FXII autoactivation.
ATR-FTIR and QCM results indicated that adsorption amounts on the PS and sPS surfaces were similar even though the surface
charge densities were different. No significant conformational change was observed from FXII adsorbed onto surfaces studied.
Using theoretical calculations, the possible contribution from the third-order nonlinear optical effect induced by the surface
electric field was evaluated, and it was found to be unable to yield the SFG signal enhancement observed. Therefore it was
concluded that the adsorbed FXII orientation and ordering were the main reasons for the remarkable SFG amide I signal increase
on sPS surfaces. These investigations indicate that negatively charged surfaces facilitate or induce FXII autoactivation on
the molecular level by imposing specific orientation and ordering on the adsorbed protein molecules.
Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users. |
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Keywords: | Sum frequency generation Factor XII Electrostatic interactions Interfacial protein structure |
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