The conjugates were analyzed by nondenaturing polyacrylamide
gel electrophoresis using an adaptation of the method of
Joseph and David (2001). A sample of 20 ll (0.5 g/l) was mixed
with an equal volume of 2 SDS (1 M Tris–HCl buffer, pH 6.8, containing
2% SDS, 5% b-mercaptoethanol, 10% glycerol, and 0.02% bromophenol
blue) protein loading buffer and boiled for 5 min.