Question

In one or two sentences, describe the usefulness of each of the following reagents in the analysis of proteins by SDS-PAGE:
(a) polyacrylamide/bis-acrylamide
(b) SDS
(c) reducing agent (dithiothreitol or β-mercaptoethanol)

Answer 1

SDS-PAGE ( Polyacrylamide Gel Electrophoresis ) is an analytical technique used to seperate and chracterize the proteins. The reagents used in this technique with their usefulness are as follows:

(a) Polyacrylamide:It is formed from acrylamide and are linear chains.

Bis-acrylamide: Bis-acrylamide cross links the polyacrylamide chains.

Pore size in the SDS-PAGE is determined  by the ratio of acrylamide to bisacrylamide. If the pore size needs to be kept large the ratio is higher and vice-versa. The pore size determines mobility.

(b). Sodium dodecyl sulfate (SDS): SDS-treated proteins have very similar charge-to-mass ratios, and similar shapes. During SDS-PAGE, the rate of migration of SDS-treated proteins is effectively determined by molecular weight. so it is used to determine moleculer weight of proteins effectly.

(c). Reducing Agent ( Dithiothreitol or β-Mercaptoethanol ):

Beta-mercaptoethanol reduces disulfide bonds and disrupts protein cross-links.

Dithiothreitol also reduces disulphide bonds and thus disrupts protein cross-links.