Alkaline Phosphatase Labeling of Antibody Using Glutaraldehyde

Abstract

The chemistry of the homobifunctional reagent, glutaraldehyde, is complex. It reacts with the amino and, to a lesser extent, the thiol groups of proteins, and when two proteins are mixed in its presence, stable conjugates are produced without the formation of Schiff bases. Self-coupling can be a problem, unless the proteins are at appropriate concentrations. In the method (1) described, there is usually little self-coupling of the enzyme or the IgG antibody. However, the size of the conjugate is large (>10⁶ Daltons), since several molecules of each component are linked. This is the simplest labeling procedure to carry out and, although the yields of enzyme activity and immunoreactivity are small, the conjugates obtained are stable and practical reagents.