Avidin is a 68KD protein that extracted from egg white. It has very high affinity to biotin molecule, one million times than the common affinity between antigen and antibody. Avidin is a alkalic protein (IP=10.0-10.5), and it can transfer to be a neutral protein through reconstruction. This antibody is obtained from the rabbit which was immunized by reconstructed avidin, and it is specific for natural and reconstructed avidin.