Tryptophan micro-scale determinations by rapid hydrolysis

A rapid acid-hydrolysis micro method was developed for the accurate determination of the tryptophan contents of proteins. Sample protein (5 micrograms) was hydrolysed in 30 microliters of 3M mercaptoethanesulfonic acid at 166 degrees C for 25 min, resulting in total hydrolysis of the peptide bonds. The subjection of the hydrolysate to an amino-acid analyser revealed the amino-acid composition, including the content of tryptophan with a high recovery of 92%.