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
The teiary structure of protein is detected by: 
Select and explain. 
A. X- ray diffraction / crystallographs., B. Spectrophotometry, C. Electrophoresis., D. Chromatography.
A: X- ray diffraction / crystallographs.
Answer: A: X- ray diffraction / crystallographs. 
Explanation: High performance (pressure) liquid chromatography (HPLC) is a modern refinement of column chromatography and is used for protein separation, purification and identification. It can not determine protein structure.Electrophoresis separates (& purifies) proteins based on migration of charged proteins in an electric field. It can not determine protein structure.Higher level (2deg, 3deg & 4deg) of protein structure is studied by X-ray crystallography, NMR sepectroscopy, infrared and ultraviolet spectroscopy.