Why perform Amino Acid Analysis?
Amino acid analysis of proteins is a method to determine the absolute amounts of individual amino acids in a sample. The method can be applied to samples containing free amino acids. However it may also be used on peptides and protein samples after hydrolysis into amino acids [1, 2].
AA analysis can be used for determination of the relative composition of amino acids in a protein. It can also be used for determination of the absolute amount of a protein or peptide if the amino acid sequence is known. Finally, it is used for purity estimation of a purified protein .
In amino acid analysis it should be noted that:
- Serine and threonine are degraded slightly during acid hydrolysis, and recoveries can be 10% lower than expected.
- Methionine can be oxidized during hydrolysis, usually less than 10% is oxidized.
- Valine and isoleucine bonds (Val-Val, Ile-Val, Val-Ile, Ile-Ile) are difficult to hydrolyse and recoveries can be 5-15% lower than expected.
- Glycine content is often higher than expected because it is a frequent contaminant due to its use in many buffers. Analysis of known amounts of AA standards is used to determine a compensation factor to correct for differences in ninhydrin reactivity [1-3].
Read more about Amino Acid quantification >>>
 Rutherfurd et al: “Amino acid analysis“, Current Protocols in Protein Science, 2009
 Rutherfurd et al: “Quantitative amino acid analysis“, Current Protocols in Protein Science, 2011
 Noble et al: “Quantification of protein“, Methods in Enzymology, 2009