Which support medium is used to determine the molecular weight of a protein?

The polyacrylamide gel is utilized for determining the molecular weight of proteins due to its ability to create a matrix that can separate proteins based on their size. This gel electrophoresis technique allows for precision in size determination because the pore size of the gel can be adjusted by varying the concentration of polyacrylamide. Smaller proteins move more quickly through the gel's matrix, while larger proteins experience more resistance and move more slowly. This differential migration enables researchers to estimate the molecular weight of the proteins by comparing their migration distances relative to standard markers of known molecular weights.

In contrast, cellulose acetate is primarily used for the separation of proteins by charge rather than size, making it less suitable for molecular weight analysis. Agar gel is predominantly used for the electrophoresis of nucleic acids rather than proteins. Agarose gel, while useful for larger nucleic acids, is not as effective as polyacrylamide gel for separating smaller proteins due to its larger pore size and lack of the fine-tuning that polyacrylamide provides. Thus, polyacrylamide gel is the optimal choice for accurately determining protein molecular weights.