This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
Protein purification and separation can be done by all except: 
Select and explain. 
A. Chromatography, B. Centrifugation, C. Electrophoresis, D. Densitometry
D: Densitometry
Answer: D: Densitometry 
Explanation: D i.e. DensitometrySDS polyacrylamide gel electrophoresis is method of protein seperation & purification on the basis of molecular sizeQ. Whereas electrophoretic mobility of protein in native (non-denaturating) gel electrophoresis and 2-D gel electrophoresis depends on both charge (PI) and its mass (hydrodynamic size). Densitometry is a method to quantitate protein in tissueQ.