This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Biochemistry
primary structure of amino acid is mainly detected by ? 
Select and explain. 
A. mass spectroscopy, B. xray crystallography, C. nmr spectrometry, D. all the above
A: mass spectroscopy
Answer: A: mass spectroscopy 
Explanation: primary structure - detected by = mass spectroscopy (edmans techinique) secondary structure /teiary structure = xray crystallography /nmr spectrometry ref : vasudevan 9th ed