A simple electrochemical method for the determination of association constants between carbohydrates and carbohydrate-binding proteins using cyclic voltammetry (CV) is described. The binding of concanavalin A (Con A) and cholera toxin (CT) to their specific α-mannose and β-galactose derivatives self-assembled on gold electrodes is electrochemically monitored with a redox probe of K3Fe(CN)6/K4Fe(CN)6. Upon binding of the proteins to the carbohydrate-modified electrodes, the redox current in CV decreases. The binding-induced change in electrochemical signal is thus used to construct Langmuir adsorption isotherm for the carbohydrate-protein interactions and to obtain the association constants. The association constants of carbohydrate-protein interactions determined by CV ((5.8 ± 1.2) × 107 M- 1 for mannose-Con A, (2.6 ± 0.5) × 108 M- 1 for galactose-CT) were in good agreement with those measured with electrochemical impedance spectroscopy and quartz crystal microbalance.
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Financial support for this work has been provided by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology ( 2012-R1A1A2006994 ).
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