Boronic acid adducts of metal dioxime complexes are useful as reagents for labeling proteins and other amine-containing compounds.

The present invention concerns an improved optical method and optical sensing device for determining the levels of polyhydroxyl-substituted organic molecules in vivo in aqueous media. Specifically, a dye is combined with a conjugated nitrogen-containing heterocyclic aromatic boronic acid-substituted bis-onium compound in the presence of a sugar, such as fructose or glucose. The viologens are preferred as the aromatic conjugated nitrogen-containing boronic acid substituted compounds. The method i...