After SDSPAGE an immunoglobulin would show bands without be

After SDS-PAGE, an immunoglobulin would show _____ band(s) without beta mercaptoethanol treatment and ________ band(s) with beta mercaptoethanol treatment. 4; 2 1; 2; 2 4 4; 1 1; 4

Solution

ANSWER IS 2;4 bands

All immunoglobulins have a four-chain structure as their basic unit. It has disulfide Inter-chain disulfide bonds and Intra-chain disulfide binds. The number of inter-chain disulfide bonds varies among different immunoglobulin molecules. Intra-chain disulfide binds - Within each of the polypeptide chains. There are also intra-chain disulfide bonds. Mercaptoethanol reduces the disulphide bonds in immunoglobulin. If disulphide bonds are connecting two polypeptide chains then mercaptoethanol would cause them to separate and therefore instead of a higher molecular weight band we get one or more lower MW bands. However, if there are disulphide bonds in the same polypeptide chain, they may cause the chain to fold up. This results in the polypeptide chain to effectively have a smaller hydrodynamic radius compared to the fully denatured chain. In such cases reducing the disulphide bonds using mercaptoethanol would cause the band to shift to a higher MW bands.