Further studies on the possibility of differential demonstration of radicals of sulphur-containing amino-acids.

The authors showed that in rat liver and brain sections with blocked SH groups and split S-S bonds mercury orange stains some tissue structures after treating the sections with BAL. Considering that the blockade of SH groups with N-ethylmaleimide in is stable the authors set forth the hypothesis that the use of BAL may enable the demonstration of a sulphur-containing amino-acid which is devoid of SH or SS groups but acquires them only when acted upon by BAL. The in vitro studies demonstrated that the effect of BAL makes it possible to stain methionine with mercury orange which otherwise does not stain this amino-acid.