Question

The next question concerns the SDS-PAGE figure below. Lane 1 contains an unknown sample. Lane M contains a mixture of the following proteins (listed alphabetically). M 1 P1 - - Protein Bovine carbonic anhydrase Bovine milk aprotinin Bovine milk lactalbumin Bovine serum albumin Beta-galactosidase Chicken egg ovalbumin Rabbit muscle myosin Soybean trypsin inhibitor Molecular Mass 29,000 6,500 14,200 66,000 116,000 45,000 205,000 20,000 - - P3 - P4 L 19. The wild type (normal) human B-chain hemoglobin protein has a molecular mass of 15,867. If B- hemoglobin is in your sample, which of the proteins in Lane 1 is it? A Pi BP2 B. P2 C. P3 D. P4 E. B-hemoglobin is not present on the gel D. 14 20. What is the point of using SDS in your PAGE protein analysis? A. It imparts a uniform charge to the proteins in your sample. B. It imparts a uniform shape to the proteins in your sample. C. It imparts a uniform size to the proteins in your sample. D. A&B E. All of the above

Answer 1

A. The correct option will be D.

In SDS-PAGE, higher molecular weight proteins will be at top as they migrate slow through the pores on the gel. So the molecular weight of each will be as follows:

205,000 116,000 66,000 45,000 29,000 20,000 14,200 6,500 - . . - - 8. hemoglobin Cas it has a molecular weight of - 15,867.) . Ph will be B. hemoglobin

B. The correct option will be D.

SDS - Sodium Dodecyl sulfate is an anionic detergent used in electrophoresis. Since SDS carries a highly negative charge and has a hydrophobic tail which interacts strongly with the polypeptide chains, it can impart a relatively uniform negative charge to all the protein molecules in the sample.

Apart from imparting a uniformly negative charge, it can denature the complex tertiary conformation of protein molecules to form linear molecules by disrupting the non-covalent protein-protein interactions. So that if confirms the uniform shape.

Now, our protein of interest has a net negative charge and a linear conformation and the rate at which they migrates in a gel primarily depends on its size.

Thank you.