An adhesive protein isolated from the marine mussel Mytilus edulis has been adsorbed to highly oriented pyrolytic graphite and enzymatically oxidized to yield a sclerotized film that is tightly bound to the substrate. Atomic force microscopy was used to image the surface and the adsorbed biopolymer, indicating uniform coverage of the substrate within 1 s of adsorption time from solution. Film thicknesses of the adsorbed protein films were estimated to be 25 and 73 Angstrom for the sclerotized films. Imaging forces ranging from less than or equal to 20 to greater than or equal to 600 nN were used to determine the stability of adhesive protein films without and with added catechol oxidase, respectively. Results indicate that the resistance of adhesive protein films to displacement can be enhanced 10-fold by enzymatic oxidation. Oxidation presumably leads to formation of covalent crosslinks between adsorbed protein chains.