Orientation of peptide, protein, and water structure at aqueous interfaces studied by vibrational sum frequency spectroscopy /
As a second order nonlinear optical spectroscopy, vibrational sum frequency spectroscopy (VSFS) is capable of investigating a variety of biological interactions at aqueous interfaces. In this study, VSFS has been applied to investigate peptide, protein, and interfacial water structure at the air/wa...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
2002.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=726462031&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | As a second order nonlinear optical spectroscopy, vibrational sum frequency spectroscopy (VSFS) is capable of investigating a variety of biological interactions at aqueous interfaces. In this study, VSFS has been applied to investigate peptide, protein, and interfacial water structure at the air/water and quartz/water interfaces. VSFS studies of lysozyme adsorption at air/water and quartz/water interfaces showed that water structure depended intimately on bulk pH at both the hydrophobic, air, and hydrophilic, quartz, interfaces. Intensity in the CH stretch range from lysozyme indicated that some protein residues became organized at the air/water interface. Interestingly, the strong electrostatic interaction with the quartz substrate also showed alignment of CH dipoles of adsorbed lysozyme when the pH was raised above 8.0. Sum frequency spectra upon adsorption of fibrinogen at pH 3.2 and 8.0 showed an increase in the ice-like peak due to the charged fibrinogen film at the interface. Adsorption at pH 5.5 also showed an increase in the ice-like peak of about 2.5 fold. The sharp ice-like peak near 3275 cm⁻¹ and a substantial decrease in the water-like peak at about 3450 cm⁻¹ indicated that interfacial water was uniformly hydrogen bonded upon adsorption of fibrinogen. A relaxation period of several minutes for the ice-like peak was observed during the adsorption process at pH 5.5. A decrease in the intensity of OH peaks at pH 5.5 and 8.0 after rinsing with pH 3.2 indicated that an irreversible change in the interfacial water structure occurred upon lowering the pH to 3.2. Sum frequency spectra of gramicidin A monolayers showed evidence for well-aligned aliphatic residues as well as aromatic residues at the air/water interface. When the molar fraction of gramicidin A in partly deuterated lipid monolayers was raised above 0.5, no significant differences in spectra were observed as the monolayer was compressed. However, dramatic changes were observed when the mole fraction of gramicidin A was below 0.5. A decrease in the CH stretch mode at low concentration of gramicidin A indicated that the net dipole of the CH stretch modes was perpendicular to the helical axis of the gramicidin A. |
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| Item Description: | Vita. "Major Subject: Chemistry". |
| Physical Description: | ix, 134 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 65-72). |