Question

Suppose a researcher calculate the dissociation constant of the binding between two imm o bilin antibodies, IG-I and IgG-2, and several antigens. He calculates the dissociation constant (R) of each IG and antipen hased on what concentration of the antiponceuses half-maximal saturation of the molecules. The value reveals the inity between the molecules and the antigens. He needs to determine which antipen specifically bindsel 1G-2 based on 1G-I binding data Antipen K (M) A 9.1 x 10 B 32 x 10" C 2 .7 x 10 1 -2 hinding data Antigen (M) A 4.0 x 10 B 7 .4 x 10 C 1 .8 x 10" Classify each antibody antipen pair based on whether the lgG binds the antigen with high or low binding affinity High allinity Low allinity

Answer 1

The smaller the K_d Value the higher will be the affinity of the ligand for its target. So according to the question,

High Affinity: IgG2 with Antigen C, IgG1 with Antigen B, IgG2 with Antigen A,

IgG2 with Antigen B

Low Affinity : IgG1 with Antigen A, IgG1 with Antigen C

IgG1 specifically binds with one of the ligand because compared to IgG2, IgG1 has lower affinity for the antigen A and C but it has more affinity towards antigen B but on the other side there is very little difference between affinities of IgG2 towards the antigens which implies the binding of IgG2 is not specific so much like the IgG1.