The method of oxidation of the oligosaccharide on the avidin by NaIO 4 leads to the generation of aldehyde groups which are further reacted with octopamine. The conjugation ratio of 5.76 octopamine per Av is testified by UV spectrum. The isoelectric point （PI） of Av is remarkably reduced by conjugating succinic acid moieties at lysine residues of Av （PI10）. The PI of suc-Av is 2.57. The combining capabilities with biotin of labelled Av derivants are greatly changed