This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Metabolism of nucleic acids, Subject name: Biochemistry
Which of the following method of protein separation is not dependent on molecular size? 
Select and explain. 
A. Gel filtration chromatography, B. Ultracentrifugation, C. Ion-exchange chromatography, D. SDS-PAGE
C: Ion-exchange chromatography
Answer: C: Ion-exchange chromatography 
Explanation: The nucleoside Inosine, Xanthosine, Guanosine is conveed into Hypoxanthine, Xanthine, and Guanine. This reaction is catalyzed by "Purine nucleoside phosphorylase". ... The hypoxanthine is conveed into Xanthine. The Xanthine is conveed into Uric acid Ref-Harpers illustrated biochemistry 30/e p684