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The alkaline hydrolysis of proteins prior to tryptophan analysis has been evaluated, and a method for the measurement of tryptophan by reverse phase h.p.1.c. after alkaline hydrolysis has been proposed and compared with published methods. Hydrolysis with either LiOH or NaOH gave similar results. Tryptophan values and the recovery of added 5-methyltryptophan were similar when hydrolysis was made under tap-water vacuum (1500 Pa) or at high vacuum (2 Pa). Partially-hydrolysed starch reduced the losses of tryptophan during hydrolysis better than thiodiglycol. High levels of indolyl-3-propionic acid or 5-methyltryptophan did not further improve tryptophan recovery. 5-Methyltryptophan is the preferred internal standard; its recovery after hydrolysis more closely resembled that of protein-bound tritiated tryptophan from goat casein than did the recoveries of a-methyltryptophan or free 14C-tryptophan. Under some conditions, the recovery of protein bound tryptophan was lower than the recovery of free tryptophan. The stability of tryptophan in hydrolysates was improved by using a phosphate buffer pH 7.0 containing 0.02% sodium azide.

Deep levels by proton and electron irradiation in 4H-SiC J. Appl. Phys. 98, 053706 (2005); 10.1063/1.2014941 Electrically active defects in irradiated 4H-SiC J. Appl. Phys. 95, 4728 (2004); 10.1063/1.1689731Evidence for negatively charged vacancy defects in 6H-SiC after low-energy proton implantation Low temperature annealing of 4H-SiC Schottky diode edge terminations formed by 30 keV Ar + implantation