<prompt> Protein separation based on moleular size ?HPLCGel filtration chromatographySalting outAffinity chromatography  <response>: Protein solubility Salting out or salt extraction precipitation of protein by ammonium sulfateMolecular size Gel filtration chromatography molecular-sieve chromatography or size exdu- sion chromatographyUltracentrifugationSDS-PAGE Sodium dodecyl sulphate-polyacrylamide gel electrophoresisDialysisMolecular charge Ionic charge Ion exchange chromatographyHigh performance liquid chromatography HPLCElectrophoresis simple on cellulose acetate starch gellsoelectric focusing a variant of electrophoresisMolecular charge and molecular weight PAGE : polyacrylamide gel electrophoresisAffinity binding Affinity chromatographyHydrophobicity Hydrophobic interaction chromatography 