SDS-Page

The intrinsic charges of proteins are obscured by

placing a strongly anionic (negatively charged) detergent, sodium dodecyl sulfate (SDS), in both the sample buffer and the gel running buffer.

The R group may be

charged or uncharged, or may be a long side chain.

SDS Page

: process by which proteins are separated based on their molecular weights.

Since the dye molecules are smaller than the proteins expected in most samples,

they move ahead of the proteins in the gel.

Proteins are made of

smaller units (monomers) called amino acids.

ratio of charge

Charge density: the to mass.

Coomassie Blue stain

: binds specifically to proteins and not to other macromolecules such as DNA or lipids.

Amino acids are joined together by

peptide bonds to form polypeptide chains.

The SDS-coated, negatively charged proteins migrate

through the gel away from the negatively charged anode toward the cathode, with the larger proteins moving more slowly than the smaller proteins.

SDS

binds to and coats the proteins and also keeps them denatured as relatively linear chains.

SDS-Page

process by which proteins are separated based on their molecular weights

Charge density

the ratio of charge to mass

The inherent charges of proteins must be

removed as a factor affecting migration in order for polyacrylamide electrophoresis to be effective as a method of protein molecular weight determination.

To effectively determine the molecular weights of proteins,

the secondary, tertiary, and quaternary structures of the protein complexes within a protein extract are disrupted prior to electrophoresis.

If the electric current is left on for too long,

the proteins will run off the bottom of the gel.