Effect of Surface Hydrophilicity and Solution Chemistry on the Adsorption Behavior of Cytochrome c in Quartz Studied Using Slab Optical Waveguide (SOWG) Spectroscopy

Jose H. SANTOS  Naoki MATSUDA  Zhi-mei QI  Akiko TAKATSU  Kenji KATO  

Publication
IEICE TRANSACTIONS on Electronics   Vol.E85-C   No.6   pp.1275-1281
Publication Date: 2002/06/01
Online ISSN: 
DOI: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Recent Progress in Organic Molecular Electronics)
Category: Optoelectronics and Photonics
Keyword: 
protein adsorption,  cytochrome c,  slab optical waveguide spectroscopy,  

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Summary: 
The adsorption behavior of cytochrome c was investigated using slab optical waveguide (SOWG) absorption spectroscopy at the near ultraviolet region utilizing thin quartz plates as planar waveguides. SOWG absorption spectra of cytochrome c measured at constant time intervals showed significant influence of surface hydrophilicity and solution chemistry on the adsorption of this important heme protein in quartz surface. Being polar and typically amphoteric, the protein preferred adsorption on hydrophilic surface than on hydrophobic surface as implied by the lower absorbance data obtained in the latter than in the former. At lower ionic strength and in the absence of buffer, the protein molecules tend to adsorb on the quartz surface. Plots of near steady-state absorbance versus protein concentration follow hyperbolic pattern in the absence of buffer or at low ionic strength and become more linear as the buffer concentration is increased. The results presented here are explained in terms of the general qualitative understanding of protein adsorption at solid-aqueous interfaces and further aids in elucidating the properties of protein monolayers and films.