title: Adsorption behavior of cytochrome c, myoglobin and hemoglobin in a quartz surface probed using slab optical waveguide (SOWG) spectroscopy.
abstract: Slab optical waveguide (SOWG) spectroscopy was used to observe the adsorption behavior of three important heme proteins, namely cytochrome c, myoglobin and hemoglobin, in a quartz surface. Using prism-coupled polychromatic visible light propagated into a quartz waveguide by internal total reflection, the real-time monitoring of evanescent wave absorption revealed a strong dependence of the protein-surface interaction on the protein concentration, the solution pH and the ionic strength. For the three proteins studied, the absorbance-bulk concentration ratio was higher at low bulk concentrations, and decreased at higher concentrations. For cytochrome c and myoglobin, the absorbance approached a limiting value, but buffered hemoglobin surprisingly did not show any indication of forming a signal plateau. Moreover, the slow introduction of protein into the solution lessened the total adsorbed amount per unit area. These observations suggested a possible conformational transition of the protein molecules at the quartz surface after adsorption. For a bulkier protein, hemoglobin, adsorption onto the quartz surface was enhanced in the presence of a phosphate buffer, while the opposite effect was observed for the smaller cytochrome c and myoglobin molecules. The results of pH studies concurred with the electrostatic interactions predicted from the isoelectric data of proteins and the quartz surface.
authors.affiliation: Nanoarchitectonics Research Center, AIST, 1-1-1 Higashi, Tsukuba 305-8565, Japan.
authors.forename: Jose H
authors.initials: JH
authors.lastname: Santos
authors.forename: Naoki
authors.initials: N
authors.lastname: Matsuda
authors.forename: Zhi-mei
authors.initials: ZM
authors.lastname: Qi
authors.forename: Takamitsu
authors.initials: T
authors.lastname: Yoshida
authors.forename: Akiko
authors.initials: A
authors.lastname: Takatsu
authors.forename: Kenji
authors.initials: K
authors.lastname: Kato
mesh_terms: D000327:Adsorption; D000818:Animals; D003574:Cytochrome c Group / Q000737:chemistry; D006420:Hemeproteins / Q000737:chemistry*; D006454:Hemoglobins / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D009211:Myoglobin / Q000737:chemistry; D009994:Osmolar Concentration; D011487:Protein Conformation; D011791:Quartz; D013057:Spectrum Analysis / Q000379:methods*; D013499:Surface Properties
chemical_list: D003574:Cytochrome c Group; D006420:Hemeproteins; D006454:Hemoglobins; D009211:Myoglobin; D011791:Quartz