Predict the patterns number of bands and apparent molecular

Predict the patterns (number of bands and apparent molecular weights) of the following proteins on SDS gels: a. A monomeric protein with a molecular weight of 35,000 Da b. A trimetric protein containing three chains, each with a molecular weight of 60,000 Da c. Immunoglobulin G (Nelson and Cox, page 178) in a non-reducing gel (no beta -mercaptoethanol added in the sample solution) - the light chains have a molecular weight of 25,000 Da and the heavy chains 50,000 Da d. Immunoglobulin G in a reducing gel (beta -mercaptoethanol added in the sample solution).

Solution

3a) a monomeric protein with a molecular weight of 35,000 Da.

Answer: Number of band = 1 and molecular weight of the band on SDS gel is 35 kilo dalton (KDa)

3b) a trimeric protein containing three chains, each with a molecular weight of 60,000 Da

Answer: Number of band = 1 and molecular weight of the band on SDS gel is 60 kilo dalton (KDa)

The three chains in the trimeric protein are joined by disulphide bonds which are broken in SDS PAGE to form three monomeric chain each of 60 KDa.

3c) Answer:

An immunoglobulin G has two light chain and two heavy chain ; both are linked by disulfide bonds. The IgG complex has molecular weight of 150 KDa. (25 KDa+25 KDa+50 KDa+50 KDa). As there is no reducing chemical in the gel,

Number of band = 1 and molecular weight of the band on SDS gel is 150 kilo dalton (KDa)

3d) IgG in a reducing gel

As Beta-Mercaptoethanol is added to the sample, it breaks all disulfide linkage present in the IgG. So all the light and heavy chains are separated and heavy chain also breaks into Fab and Fc region each having 25 KDa.

Number of band = 1 and molecular weight of the band on SDS gel is 25 kilo dalton (KDa)