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Chemical modification, electrochemistry and immunoassays of glycoproteins and glycans

Osmium eight-valent complexes react with pyrimidine bases in nucleic acids and with tryptophan in proteins, while six-valent [Os(VI)L] complexes (where L is a nitrogenous ligand) react with glycans as well as with ribose at the 3-end in RNA. We showed that Os(VI) complexes bind to 1, 2-diols in polysaccharides and oligosaccharides, producing voltammetric responses similar to those of DNA- Os(VIII)L adducts. Recently we have shown that glycans can be modified directly in glycoproteins and detected electrochemically down to pM concentrations. In addition we developed a monoclonal antibody Manost 2.1 in mice after immunization with the adduct of mannan with Os(VI)temed complex (temed is N, N, N′, N′-tetramethylethylenediamine). The specificity of this antibody to different biomolecules treated with Os(VI)temed was tested using dot blot immunoassay. Manost 2.1 showed specificity toward Os(VI)temed-modified polysaccharides, glycoproteins and ribonucleotide at the 3’-end in DNA. The antibody did not recognize either the unmodified compounds or non-glycosylated proteins treated with Os(VI)temed. We performed western blotting and Coomassie blue staining of mixtures of biomacromolecules treated with Os(VI)temed and identified specifically the modified glycoproteins. The immunochemical method using Manost 2.1 was compared with electrochemical analyses based on reduction signals of the Os(VI)temed adducts, with similar results in terms of sensitivity. This new antibody-based approach opens the door for rapid and inexpensive analysis of glycans and glycoproteins in various scientific and medical fields.

Carbohydrate chemical modification ; Os(VI) complexes ; antibody against chemically modified carbohydrates ; glycoprotein adduct immunoassays ; voltammetry of chemically modified glycoproteins

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