title: Identification of the response of protein N-H vibrations in vibrational sum-frequency generation spectroscopy of aqueous protein films.
abstract: The N-H stretching vibration is an important probe for investigating structural and functional properties of proteins but is often difficult to analyze as it overlaps with the O-H stretching vibration of water molecules. In this work we investigate the N-H signals of hydrophobins using conventional (VSFG) and heterodyne-detected vibrational sum-frequency generation spectroscopy (HD-VSDG). Hydrophobins represent a group of surface active proteins that form highly-ordered protein films at the water-air interface and that give rise to prominent vibrational modes. We find that in conventional VSFG spectra N-H specific signals show significant changes in shape and intensity upon altering the pH values. These changes can easily be misinterpreted for conformational changes of the protein. Using HD-VSFG experiments, we demonstrate, that for hydrophobin films the change of the N-H response with pH can be well explained from the interference of the N-H response with the broad interfacial water O-H stretch band.
authors.affiliation: AMOLF, Science Park 104, 1098XG Amsterdam, The Netherlands. K.Meister@amolf.nl.
authors.forename: K
authors.initials: K
authors.lastname: Meister
authors.forename: A
authors.initials: A
authors.lastname: Paananen
authors.forename: H J
authors.initials: HJ
authors.lastname: Bakker
mesh_terms: D006859:Hydrogen / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D009584:Nitrogen / Q000737:chemistry*; D011506:Proteins / Q000737:chemistry*; D013057:Spectrum Analysis; D014732:Vibration; D014867:Water / Q000737:chemistry
chemical_list: D011506:Proteins; D014867:Water; D006859:Hydrogen; D009584:Nitrogen