What are principles of analytic methods  (electrophoresis, isoelectric focusing, 2-D electrophoresis).

-electrophoresis/ Another important technique for the separation of pro- teins is based on the migration of charged proteins in an electric field, proteins can be visual- ized as well as separated, permitting a researcher to estimate quickly the number of different proteins in a mixture or the degree of purity of a particular protein preparation. - isoelectric focusing/is a procedure used to determine the isoelectric point (pI) of a protein, A pH gradient is established by allowing a mixture of low molecular weight organic acids and bases (ampholytes) to distribute themselves in an electric field generated across the gel. When a protein mixture is applied, each protein migrates until it reaches the pH that matches its pI. Proteins with different isoelec- tric points are thus distributed differently throughout the gel. 2-D electrophoresis/ permits the resolution of complex mixtures of proteins, Two-dimensional electrophoresis sepa- rates proteins of identical molecular weight that differ in pI, or proteins with similar pI values but different molecular weights.