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Experimental evidence of the reversibility of the first stage of protein adsorption at a hydrophobic quartz surface near the isoelectric point
Author(s) -
Santos Jose H.,
Matsuda Naoki,
Qi Zhimei,
Yoshida Takamitsu,
Takatsu Akiko,
Kato Kenji
Publication year - 2003
Publication title -
surface and interface analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.52
H-Index - 90
eISSN - 1096-9918
pISSN - 0142-2421
DOI - 10.1002/sia.1551
Subject(s) - adsorption , isoelectric point , absorbance , chemistry , gibbs free energy , cytochrome c , analytical chemistry (journal) , protein adsorption , absorption (acoustics) , langmuir , chemisorption , isoelectric focusing , langmuir adsorption model , chromatography , organic chemistry , materials science , thermodynamics , biochemistry , physics , mitochondrion , composite material , enzyme
The reversibility of the first stage of adsorption of zwitterionic cytochrome c on a hydrophobic quartz surface was investigated using time‐resolved slab optical waveguide (SOWG) absorption spectroscopy. Using a novel prism‐free broadband coupling approach, absorbance data were collected successfully at a 50 ms time interval during the first few seconds after solution–surface contact. Near the isoelectric point where the cytochrome c molecules possess a net charge of zero and hence cannot be influenced by an electric field, the speed at which adsorption proceeded was found to be dependent on cytochrome c concentration as well as on surface hydrophobicity. It was also observed that the degree of protein adsorption increased as the surface hydrophobicity was increased. Within 6 s the adsorption process appeared to be reversible, as revealed by extremely low chi‐squared values when the absorbance data were fitted into the reversible Langmuir‐type kinetic model. The standard Gibbs free energy of adsorption was also calculated from the absorbance data. Copyright © 2003 John Wiley & Sons, Ltd.