What is the sample preparation procedure to isolate and quantify cysteine from protein samples? - WKB50231

ENVIRONMENT

• Amino acid analysis
• AccQ•Tag
• Accq•Tag Ultra

ANSWER

The amino acids cysteine and cystine undergo degradation with standard protein hydrolysis protocols. To analyze the cysteine monomer and quantify it in a protein, the sample preparation performed can be performic acid oxidation (to analyze total cystine and cysteine) or alkylation and reduction with either carboxymethylation or vinylpyridine.

ADDITIONAL INFORMATION

For additional information, see the following journal article:

Fountoulakis M. and Lahm HW. "Hydrolysis and amino acid composition analysis of proteins." Journal of Chromatography A, 826(1998) 109-134.

See also USP General Chapter 1052: Biotechnology derived articles for amino acid analysis

Also see:

Comprehensive Guide to Hydrolysis and Analysis of Amino Acids Primer  (on-line guide) 

• See section 2.3. HYDROLYSIS METHODS FOR ANALYSIS OF SULFUR-CONTAINING AMINO ACIDS (CYSTEINE, CYSTINE, AND METHIONINE)  

Waters also sells this guide in a soft covered book as well:   

SKU: 715006455 - Hydrolysis and Analysis of Amino Acids from Purified Peptides/Proteins, Foods, and Feeds