Final answer:
Sodium dodecyl sulfate (SDS) is used in Buffer P2 as a detergent to denature proteins and to provide them with a uniform negative charge, facilitating their size-based separation during SDS-PAGE.
Step-by-step explanation:
The role of Sodium dodecyl sulfate (SDS) in Buffer P2 is primarily related to its function as a detergent in the process of SDS-polyacrylamide gel electrophoresis (SDS-PAGE). SDS denatures proteins by disrupting non-covalent bonds which causes proteins to lose their tertiary and quaternary structure. This allows proteins to take on a more linear form. More importantly, SDS imparts a negative charge to the proteins in proportion to their length. This consistent negative charge per unit length allows the proteins to be separated by size when an electric current is applied, as they will all move toward the positively charged anode at a rate inversely proportional to their size in the gel matrix.
During the preparation for SDS-PAGE, proteins are treated with SDS to ensure they carry this uniform negative charge. In the context of 2D electrophoresis, the treatment with SDS buffers occurs after proteins have been separated by isoelectric point in the first dimension and ensures that proteins are properly prepared for the second dimension of separation, which is the SDS-PAGE.