Question

Give the approximate molecular masses of an immunoglobulin G molecule analyzed by (a) gel filtration chromatography, (b) SDS-PAGE, and (c) SDS-PAGE in the presence of 2-mercaptoethanol.

Short answer

The approximate molecular mass of an immune globulin G molecule analyzed by (a) gel filtration chromatography is 150 kDa, (b) SDS-PAGE is 200-250 kDa, and (c) SDS-PAGE in the presence of 2-mercaptoethanol is 150 kDa.

Step-by-step solution

Molecular mass of an Immunoglobulin G molecule analyzed by (a) gel filtration chromatography

The gel filtration chromatography of an immunoglobulin G molecule will show the molecular weight of two heavy chains and two light chains. The approx. molecular weight of a heavy chain and a light chain are 50 kDa and 25 kDa, respectively.

Thus the total molecular weight analyzed by gel filtration chromatography should be = (2 * 25 + 2 * 50) kDa = 150 kDa

Molecular mass of an Immunoglobulin G molecule analyzed by (b) SDS-PAGE

The molecular mass in an SDS-PAGE will reflect the mass of a native Immunoglobulin G molecule. Now, the Fc region of the native molecule will be glycosylated. This incident gives the mass of the molecule to be higher: approx. 200-250 kDa

Molecular mass of an Immunoglobulin G molecule analyzed by (c) SDS-PAGE in the presence of 2-mercaptoethanol

The immunoglobulin molecules contain multiple disulfide bonds. In the presence of 2-mercaptoethanol, those disulfide bonds will be broken and the molecule will be denatured.

The denatured immunoglobulin molecule will show a molecular mass of approx. 150 kDa as analyzed by an SDS-PAGE.