ABSTRACT
α-Methyl-norvaline, an amino acid whose structure resembles both valine and leucine, has been found in certain circumstances to inhibit haemoglobin formation in the area vasculosa of the 48-hr. chick embryo. In the present experiments tracer methods have been used to show that it inhibits the uptake of both valine and leucine into protein of the embryos, and that analogue is itself taken up into protein. There is no evidence in autoradiographs of any differential effect of the analogue on amino acid uptake into blood cells. It had been suggested earlier, however, that the analogue may compete with valine (and possibly also with leucine) for uptake into terminal positions on the peptides ofhaemo-globin. Further experiments will aim at detecting whether, and at what sites, the analogue is taken up into the haemoglobin itself.