support under contract number ca 29995 by the u s the government has certain rights in the invention application_number US 8715787 A description referring to fig1 when examined by electron microscope utilizing rotary shadowing techniques the structure of laminin appears as an asymmetric cross the three short arms each have two globular domains and are 37 nm in length the long arm exhibits one large terminal globular domain and is 77 nm in length engel et al supra as seen in fig1 the three chains are associated via disulfide bonds and other bonds of the three polypeptide chains only the b1 chain having a molecular weight of 215 000 has been published sasaki et al supra the complete sequence of the b1 chain is shown in fig2 in fig3 a schematic of the domain structure of the b1 chain is shown according to sasaki et al supra binding sites for heparin are of special interest since heparin like macromolecules such as heparan sulfate proteoglycans are present in basement membranes and cell surfaces and therefore their association with laminin may affect basement membrane structure and diverse cellular functions as indicated previously it is known that a heparin binding site exists on the a chain in the globule of the long arm of laminin ott et al supra the exact amino acid sequence is not known and therefore no related oligopeptide.