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
Which of the following is not a technique for protein precipitation? 
Select and explain. 
A. Trichloroacetic acid, B. Heat precipitation, C. Isoelectric point method, D. Titration with reducing sugar
D: Titration with reducing sugar
Answer: D: Titration with reducing sugar 
Explanation: Ans: D. Titration with reducing sugar(Ref Harper 30/e p26)Titration with reducing sugar is not used for protein precipitation.Protein precipitation:Widely used to concentrate proteins & purify them from various contaminants.Used for isolating specific protein in quantities sufficient for analysis.Requires multiple successive purification techniques.Classic approaches:Based on,Isoelectric precipitation - Differences in relative solubility of individual proteins as pH function.Precipitation with ethanol or acetone - Polarity.Salting out with ammonium sulfate.Paper chromatography including TLCD.