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Chinese Science Bulletin 03/2013; · 1.32 Impact Factor
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ABSTRACT: Previously, we developed several methods to use sum frequency generation (SFG) vibrational spectroscopy to probe buried polymer/metal interfaces in situ by depositing polymer films with different thicknesses on metal surfaces or sandwiching a polymer thin film between a metal surface and a fused silica window. In this study, we developed a new and easier method to directly probe the polymer/ metal interface by collecting ppp SFG spectra using a poly(ethyl methacrylate) (PEMA)/silver (Ag) interface as an example. We confirmed that for a thin polymer film on metal, the dominant SFG signals were contributed from the polymer surface in air and/ or the polymer metal interface, while the contribution from the polymer bulk could be ignored. Previously, we showed that the ssp spectra were contributed by both the polymer/air and polymer/metal interfaces. Here we demonstrated that the SFG ppp spectra were dominated by signals from the buried polymer/metal interface from which the structural information on the buried interface can be deduced. This method to probe the buried polymer/metal interface via SFG is relatively simple compared to our previous sample preparation techniques and/or data analysis methods.
Macromolecules 07/2012; · 5.17 Impact Factor
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ABSTRACT: Sum frequency generation (SFG) vibrational spectroscopy has been applied to the investigation of peptide immobilization on a polymer surface as a function of time and peptide conformation. Surface immobilization of biological molecules is important in many applications such as biosensors, antimicrobial materials, biobased fuel cells, nanofabrication, and multifunctional materials. Using C-terminus-cysteine-modified cecropin P1 (CP1c) as a model, we investigated the time-dependent immobilization behavior in situ in real time. In addition, potassium phosphate buffer (PB) and mixtures of PB and trifluoroethanol were utilized to examine the effect of peptide secondary structure on CP1c immobilization to polystyrene maleimide (PS-MA). The orientation of immobilized CP1c on PS-MA was determined using polarized SFG spectra. It was found that the peptide solution concentration, solvent composition, and assembly state (monomer vs dimer) prior to immobilization all influence the orientation of CP1c on a PS-MA surface. The detailed relationship between the interfacial peptide orientation and these immobilization conditions is discussed.
Langmuir 06/2011; 27(11):7042-51. · 4.19 Impact Factor
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ABSTRACT: Planar solid supported single lipid bilayers on mica, glass, or other inorganic surfaces have been widely used as models for cell membranes. To more closely mimic the cell membrane environment, soft hydrophilic polymer cushions were introduced between the hard inorganic substrate and the lipid bilayer to completely avoid the possible substrate-lipid interactions. In this article, sum frequency generation (SFG) vibrational spectroscopy was used to examine and compare single lipid bilayers assembled on the CaF(2) prism surface and on poly (L-lactic acid) (PLLA) cushion. By using asymmetric lipid bilayers composed of a hydrogenated 1,2-dipalmitoyl-sn-glycerol-3-phosphoglycerol (DPPG) leaflet and a deuterated 1,2-dipalmitoyl-(d62)-sn-glycerol-3-phosphoglycerol (d-DPPG) leaflet, it was shown that the DPPG lipid bilayers deposited on the CaF(2) and PLLA surfaces have similar structures. SFG has also been applied to investigate molecular interactions between an antimicrobial peptide Cecropin P(1) (CP1) and the lipid bilayers on the above two different surfaces. Similar results were again obtained. This research demonstrated that the hydrophilic PLLA cushion can serve as an excellent substrate to support single lipid bilayers. We believe that it can be an important cell membrane model for future studies on transmembrane proteins, for which the possible inorganic substrate-bilayer interactions may affect the protein structure or function.
The Journal of Physical Chemistry C 04/2011; 115(15):7613-7620. · 4.80 Impact Factor
