***Effective June 28, 2013, the Keck Biotechnology Resource Laboratory will discontinue the following services: Amino Acid Analysis, Protein Sequencing (Edman Degradation), Large- and Small-Scale Peptide Synthesis. Small-Scale Peptide Synthesis is no longer accepting orders. Please contact us for the last dates for order or sample submission related to other services.
Accurately (+/-10%) determining the concentration of a bench stock or the ug protein in a sample is the most common use of amino acid analysis. Given the typical low abundance of cysteine and tryptophan in proteins, we recommend HCl hydrolysis and analysis for this purpose because PAO destroys the more abundant tyrosine along with tryptophan and MSA under-reports total protein.
Synthetic peptides are a combination of peptide and the salt bound to every Arginine, Lysine, Histidine, unmodified N-terminus, and amidated C-terminus. Because of this, weighing out 1 mg of lyophilized peptide powder and dissolving it in 1 ml of solvent does not give a 1 mg/ml peptide solution.
Amino acid analysis can be used to determine the ratio of known proteins in a complex or simple mixture. In most cases the proteins are separated by SDS-PAGE and the Coomassie-stained gel bands are submitted for HCl hydrolysis and analysis.
A common tool used by X-ray crystallography is the incorporation of seleno-methionine. After acid hydrolysis seleno-methionine is detected as several peaks, one or more of which coelute with other amino acids. Therefore, we calculate the % incorporation by the absence of normal methionine.
Many unusual or modified amino acids can be quantitated with our analyzer. Modifications cannot be acid-labile unless the project is only concerned with free amino acids. (Ex: Acetylation is removed from the lysine side-chain during HCl hydrolysis)
Residual allergenic protein in food oils or other raw materials is a concern to manufacturers, so amino acid analysis is sometimes used to show the absence of protein in a sample. Detectable protein is often reported as µg/g or parts-per-million (ppm) in the sample.
Some samples contain significant amounts of amino acids that are not bound in protein that skew experimental results or the predicted composition determined by amino acid analysis. In these cases it is useful to analyze an aliquot of the sample to quantitate the amounts of free amino acids so that they can be subtracted from the results.