Abstract: An electrochemical method of identifying the presence of a target protein in a sample is provided. The method comprises providing a redox probe modified to include a detector that is suitable to bind to the target protein, and exposing the sample to the detector-modified redox probe. A change in the electrochemical signal produced by the redox probe as compared to a control signal is indicative of the presence of the target protein.

Abstract: A nucleotide triphosphate (NTP) participates in a phosphorylation reaction, wherein a phosphate group is transferred from the NTP to a substrate by a kinase. Provision in a kinase reaction of a NTP whose gamma phosphate is conjugated to an electroactive label results in the transfer of the gamma phosphate-electroactive label conjugate from the NTP to the substrate. The electroactive label is an organic moiety such as a quinone or a nitroheterocycle, or is a metallocene such as a ferrocene or a cobaltocene. Upon transfer of the gamma phosphate-electroactive label conjugate to an electrode-bound substrate by a kinase, the phosphorylation event is detected electrochemically by cyclic voltammetry. Phosphorylation can also be detected by mass spectrometry of a substrate carrying the electroactive label-conjugated gamma phosphate.

Abstract: [Problems] A highly sensitive and accurate determination of a test substance is achieved without the need of complicated procedures. [Means for solving the Problems] The presence or absence or the concentration of a test substance 3 can be determined by gathering around the surface of a working electrode 1 metal microparticles 5 in an amount corresponding to the amount of the test substance 3 contained in a test solution, oxidizing the metal microparticles 5 electrochemically, measuring the value of a current produced by electrochemically reducing the oxidized metal, and determining the presence or absence or the concentration of the substance 3 based on the current value. It is preferred that the electrochemical oxidation of the metal microparticles 5 be conducted while maintaining the potential of the working electrode 1 at a value equal to a potential employed for the electrochemical oxidization of the metal microparticles 5.