Lakhasly

In SDS-PAGE, the gel is cast in a buffer containing sodium dodecyl sulfate (SDS), an anionic detergent.By heating the protein sample between 70-100?C in the presence of excess SDS and thiol reagent, disulfide bonds are cleaved, and the protein is fully dissociated into its subunits.The simplicity and speed of this method, plus the fact that only microgram quantities of protein are required, have made SDS-PAGE the most widely used method for determination of molecular mass in a polypeptide sample.

In SDS-PAGE, the gel is cast in a buffer containing sodium dodecyl sulfate (SDS), an anionic detergent. SDS denatures proteins by wrapping around the polypeptide backbone. By heating the protein sample between 70-100°C in the presence of excess SDS and thiol reagent, disulfide bonds are cleaved, and the protein is fully dissociated into its subunits. Under these conditions most polypeptides bind SDS in a constant weight ratio (1.4 g of SDS:1 g of polypeptide). The intrinsic charges of the polypeptide are insignificant compared to the negative charges provided by the bound detergent so that the SDS-polypeptide complexes have essentially the same negative charge and shape. Consequently, proteins migrate through the gel strictly according to polypeptide size with very little effect from compositional differences. The simplicity and speed of this method, plus the fact that only microgram quantities of protein are required, have made SDS-PAGE the most widely used method for determination of molecular mass in a polypeptide sample. Proteins from almost any source are readily solubilized by SDS so the method is generally applicable.