Quantitative analysis of tryptophan modified by 2-hydroxy-5-nitrobenzyl reagents after hydrolysis with p-toluenesulfonic acid

On the reactivities of the tryptophan residues of human alpha-lactalbumin to 2-hydroxy-5-nitrobenzyl bromide

The reaction of human alpha-lactalbumin with the tryptophan reagent 2-hydroxy-5-nitrobenzyl bromide has been studied. This protein has 3 tryptophan residues (Trp-60, Trp-104 and Trp-118) all of which are accessible to the reagent at pH 2.7 or 7. Trp-60 of human alpha-lactalbumin is much more reactive than Trp-60 of bovine alpha-lactalbumin (Barman, T. E. (1972) Biochim. Biophys. Acta 257, 297-313). As with bovine alpha-lactalbumin, at pH 2.7, 2-hydroxy-5-nitrobenzyl bromide is specific for tryptophan but at pH 7 His-32 also reacts. When treated with the tryptophan reagent, both alpha-lactalbumins lose their specifier protein activities in the lactose synthase (UDPgalactose:D-glucose 4-beta-galactosyltransferase, EC 2.4.1.22) reaction.

A collaborative study on the determination of tryptophan in feedingstuffs

The results are reported of collaborative work carried out at eight laboratories to assess the Miller1 and Spies and Chambers2 procedures for the determination of tryptophan in protein concentrates and gave values for groundnut, soya bean and cottonseed meals of 1.0, 1.4 and 1.2 g/16 g N, respectively. The results obtained by both methods were similar, though collaborators preferred the Miller method.