| Abstract
| - Fluorescence quenching techniques are used to investigate the accessibility of a model biorecognition element−reporter group system when in buffer, surface-adsorbed,and covalently attached to a silica surface. The site-selective fluorescent reporter group,6-acryloyl(dimethylamino)naphthalene (acrylodan, Ac), is attachedcovalently(at cysteine-34) to bovine and human serum albumin(BSA and HSA, respectively) and serves as a surrogaterecognition element−reporter group system.Molecularoxygen is used to quench the Ac fluorescence and theaccessibility, in the form of bimolecular rate constants(kq), in each model system is quantified.Although onemight expect these systems to exhibit similar behavior,differences in quenching characteristics are observed,such as wavelength dependency of the Stern−Volmerquenching constant (KSV) for the native proteinsin buffer.BSA-Ac exhibits wavelength dependent KSVvalues as wellas a blue-shifted emission spectrum on O2addition.Physisorption of BSA-Ac onto a fused-silica opticalfiberlowers the accessibility of Ac to O2, whereascovalentattachment of BSA-Ac to APTES/glutaraldehyde-modifiedsilica enhances the accessibility of the Ac reportergroupto O2.
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