Question

When purifying a protein (ADH) in a biochemistry lab, what does it mean if you have a significant drop in % yield, fold purification and a see a decrease in specific activity?

Answer 1

To find the sucess of protein purification, we have to look at certain parameter such as specific activity by SDS-PAGE. The first purification step, salt fractionation, leads to an increase in purity of only 3 folds, but we can recover near by all target protein in origional extract, given that the yield is 92%.later on the fractionation is passed through the ion exchange column. the purification will now increase to 9 fold compared with origional extract, wheras the yield falls to 77%.molecular exclusion chromatography brings the level of purification to 100- fold, but the yield is now at 50% . the final step is affinity chromatography with the use of a ligand specific for the target proteins, this is powerfull purification step up to level of 3000 folds, while lowering the yiwld to 35%.

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