SYNTHESIS AND CHARACTERIZATION OF MALONIC ACID DIHYDRAZIDE AND ITS METAL COMPLEXES

A new series of complexes was synthesized by the reaction between malonyl dihydrazide (MAH) and manganese, copper, nickel, zinc, cadmium, cobalt and ferric salts in methanolic medium. The complexes were characterized by elemental analysis, molar conductance measurements, electronic, IR and 1H NMR spectral studies. Based on the results obtained, the stoichiometry of Fe(III)-MAH and Co(III)-MAH was proposed to be 1:3 and that for Cu(II)-MAH, Cd(II)-MAH, Zn(II)-MAH, Mn(II)-MAH, Ni(II)-MAH was proposed to be 1:2 (M:L). It was suggested that the nitrogen present in the azomethine (>C=N-) group of the enolic form present in the ligand was involved in the formation of complexes. A clear picturisation indicating the bonding sites were depicted for each complex. The metal complexes exhibit different geometries such as tetrahedral, square planar and octahedral arrangements.

Reversible and irreversible cross-linking of immunoglobulin heavy chains through their carbohydrate residues

After periodate oxidation and incubation with a dihydrazide, cross-linking of the two heavy chains of immunoglobulins G from several species proceeds specifically through their oligosaccharides. We have used malonic acid dihydrazide, adipic acid dihydrazide and dithiodipropionic acid dihydrazide. The last compound is introduced in this work as a cleavable-carbohydrate-specific cross-linker. It was found that in rabbit and human immunoglobulins the degree of cross-linking was strongly dependent on the oxidation conditions but only very weakly dependent on the concentration and size of the dihydrazides. Papain cleavage of the cross-linked rabbit IgG indicated that the cross-linking occurred predominantly, if not exclusively, in the Fc region, probably through the two glycans linked to Asn-297 in the CH2 domain of each of the two heavy chains. The immunoglobulins from sheep, pig, goat and guinea pig show a comparable cross-linking pattern, indicating that the sugar chains from these immunoglobulins have a spatial structure closely related to that of rabbit and human IgG. When dithiodipropionic acid dihydrazide was used as the cross-linker, the cross-link could be cleaved by mercaptoethanol.