Analytical Sciences

Abstract − Analytical Sciences, 28(3), 251 (2012).

Voltammetric Sensing of Phosphoproteins Using a Gallium(III) Acetylacetonate-Modified Carbon Paste Electrode
Kazuharu SUGAWARA,* Asako YUGAMI,** and Toshihiko KADOYA*
*Maebashi Institute of Technology, Gunma 371-0816, Japan
**Faculty of Education, Gunma University, Gunma 371-8510, Japan
The voltammetric detection of phosphoproteins was developed using a gallium(III) acetylacetonate-modified carbon paste electrode. Because phosphate groups of the protein interacted with the gallium(III) ion, the protein was accumulated on the electrode surface. A hexaammine ruthenium(III) ion, which combined with the functional groups, was used to monitor the interaction. When phosvitin and hexaammine ruthenium(III) ions were incubated in 0.1 M acetate buffer (pH 3.2), a reduction peak of hexaammine ruthenium(III) ion at the electrode decreased as the concentration of the protein increased. In contrast, an increase in the peak current was observed with a plain carbon paste electrode. These results were caused by a competitive reaction of the phosphate groups with the hexaammine ruthenium(III) and gallium(III) ions. In the presence of α-, β- and κ-caseins, the electrode response decreased due to the order of the numbers of phosphate groups. This method could be applied to the sensing of phosphoproteins at the 10−10 M level.