Polymerization of proteins with glutaraldehyde. Soluble molecular-weight markers

Glutaraldehyde is well known for its ability to react with proteins and to produce insoluble cross-linked aggregates. In contrast with this situation, conditions are described here which yield covalently linked soluble protein oligomers. The procedure is applicable to a wide range of proteins, and by slight variation in the reaction conditions, soluble polymers in the molecular weight range 3x10(4)-2x10(7) were produced. The products are valuable as molecular-weight markers, e.g. in sodium dodecyl sulphate-polyacrylamide-gel electrophoresis. The inherent similarities of these oligomers make them superior to commercial molecular-weight protein markers, which may have marked differences in composition and charge.