Question

Separation of protein by molecular weight by adding negative charge to them is:

1. electricity

2. SDS

3. flow from cathode to anode

4. adjusted pH

5. Dialysis

5.

Answer 1

Proteins are macromolecules consist of amino acid monomers and have different charges because of their amino acid composition. Polyacrylamide-gel electrophoresis is a technique by which proteins are separated and analyzed.

The option "2" SDS is the right answer. In electrophoresis, proteins are separated by molecular weight by adding negative charge to them is SDS. SDS (sodium dodecyl sulfate) is a detergent. Treatment of protein samples with SDS makes all proteins uniformly negatively charged and when current is supplied in gel, different proteins are separated on gel according to their molecular weight from the anode (negatively charged electrode) to the cathode (positively charged electrode).

Electricity is a term used and linked with molecules having electric charged. When it is provided, molecules move to the opposite side depending upon the charge they carry. Such as overall negatively charged proteins (after treatment with SDS) move from negative to the positive electrode. Therefore, electricity is not the right answer. Flow from cathode to anode is the movement of positively charged molecules from the positive electrode to the negative electrode. It can not be added to the proteins therefore, this is also not the right answer. The pH is a scale that gives the idea about the acidity or basic nature of molecules. All proteins have a unique composition of amino acids and because of this at a given pH all proteins have different charge therefore, adjusted pH is not the right answer. Dialysis is a process used to separate small molecules and protein through a semipermeable membrane and therefore, dialysis is not the right answer.