The subsites of monoclonal anti-dextran IgA W3129.

Synthetic deoxyfluoro derivatives of methyl alpha-D-glucopyranoside, as well as methyl alpha-glycosides of isomalto-oligosaccharides, some having fluorine substituted for hydroxyl groups at selected positions, have been evaluated for their binding with a myeloma monoclonal IgA known to bind only to an oligosaccharide sequence at the nonreducing end of alpha-(1----6)-linked D-glucopyranans (dextrans). The results are compatible with the antibody's possessing one subsite of high affinity for its D-glucosyl group, the remaining three subsites having low affinities for their respective D-glucosyl residues. The high-affinity antibody-subsite occurs at the interior end of the sequence of four subsites, appears to be relatively accessible, and binds the (terminal) nonreducing D-glucosyl group of the oligosaccharidic determinant using two, and possibly three, hydroxyl groups in hydrogen bonding.