Electroanalysis of Enzyme Activity in Small Biological Samples: Alkaline Phosphatase.

The discovery of sulfite-stabilized anodic current of hydroquinone (HQ) at high pH was used to develop two new methods for measuring the activity of the key biomarker alkaline phosphatase (ALP). Both approaches relied on the monitoring of ALP-triggered release of HQ from a substrate hydroquinone diphosphate (HQDP) into a pH 10.00 solution.

Oxidases, carbon nanotubes, and direct electron transfer: A cautionary tale.

The case study of four FAD-dependent oxidase enzymes is presented in the context of the often-claimed direct electron transfer (DET) to glucose oxidase at carbon nanotubes (CNT). The selected enzymes included d-amino acid (AAOx), alcohol (AOx), pyranose (PyOx), and choline oxidase (ChOx). Each enzyme (E) was mixed with chitosan and CNT (either multi- or single-walled) to form a CNT/E film on the surface of glassy carbon electrode.

Synthesis and Characterization of Pyridine Compounds for Amperometric Measurements of Leukocyte Esterase.

We introduce a new class of substrates (compounds I-III) for leukocyte esterase (LE) that react with LE yielding anodic current in direct proportion to LE activity. The kinetic constants K and k for the enzymatic reactions were determined by amperometry at a glassy carbon electrode. The binding affinity of I-III for LE was two orders of magnitude better than that of existing optical LE substrates.