linked only by disulfide bonds. Reduction will yield two or more polypeptide fragments ch will migrate independently. In the same way oligomeric proteins(e. g, hemoglobin) will dissociate into monomeric subunits when solubilized by SDs. For this reason, hemoglobin migrates as a monomer of molecular weight 16,000 rather than a tetramer of 64, 500 D. The subunit dissociation caused by SDs is one reason why oligomeric proteins must be characterized by both SDS and disc electrophoresis. The pore size of the gel network is the critical factor in SDS-PAGE separations. The average pore size can be decreased by either increasing the total concentration of monomer(both acrylamide and bis)or by increasing the proportion of cross-linker( BiS)to the total monomer in the gel. Table 1 gives the approximate molecular weight ranges that can be conveniently estimated with gels of various total monomer concentrations, expressed as percent-gel Yogel=(g Acrylamide+ g BIS)/100ml x 100 Table 1 moleCular weight ranges for sds-page Totalacrvlamide 15 %o gel) ange 10-70 25-200 Kilodaltons) This methods separates proteins based primarily on their molecular weights(Laemmli 1970) Among the varied uses of this technique are 1. Analysis of protein purity 2. Determination of protein molecular weight; 3. Verification of protein concentration 4. Detection of proteoly 5. Identification of immunoprecipitated proteins 6. First stage of immunoblotting; 7. Detection of protein modification 8. Separation and concentration of protein antigens for antibody production; 9. Separation of radioactively labeled proteins. Sensitivity of staining: 1. Coomassie Blue: 0. 1-1 ug per band(Smith, 1984); 2. Silver Staining: 2-10 ng per band giulian et aL, 1983).195 linked only by disulfide bonds. Reduction will yield two or more polypeptide fragments which will migrate independently. In the same way oligomeric proteins(e.g., hemoglobin) will dissociate into monomeric subunits when solubilized by SDS. For this reason, hemoglobin migrates as a monomer of molecular weight 16,000 rather than a tetramer of 64,500 D. The subunit dissociation caused by SDS is one reason why oligomeric proteins must be characterized by both SDS and disc electrophoresis. The pore size of the gel network is the critical factor in SDS-PAGE separations. The average pore size can be decreased by either increasing the total concentration of monomer(both acrylamide and BIS) or by increasing the proportion of cross-linker(BIS) to the total monomer in the gel. Table 1 gives the approximate molecular weight ranges that can be conveniently estimated with gels of various total monomer concentrations, expressed as percent-gel. %gel = (g Acrylamide + g BIS)/ 100ml x 100 Table 1. MOLECULAR WEIGHT RANGES FOR SDS-PAGE Total Acrylamide (% gel) 15 10 5 M.W. Range (Kilodaltons) 3-50 10-70 25-200 This methods separates proteins based primarily on their molecular weights (Laemmli, 1970). Among the varied uses of this technique are: 1. Analysis of protein purity; 2. Determination of protein molecular weight; 3. Verification of protein concentration; 4. Detection of proteolysis; 5. Identification of immunoprecipitated proteins; 6. First stage of immunoblotting; 7. Detection of protein modification ; 8. Separation and concentration of protein antigens for antibody production; 9. Separation of radioactively labeled proteins. Sensitivity of staining: 1. Coomassie Blue: 0.1~1 g per band (Smith, 1984); 2. Silver Staining: 2~10 ng per band (Giulian et al., 1983)