Chemical Analysis of Proteins Low in Aromatic Amino-acids

Abstract

METHODS for protein estimation in common use such as ultra-violet absorption and the method of Lowry et al.¹ rely on the presence in the molecule of the aromatic amino-acids tyrosine and tryptophan, and if these are present in low concentrations, estimates of protein will be subject to error. Our in vivo investigations into blood coagulation² have revealed that the active moiety, serum thrombotic accelerator³, which plays an important part in this mechanism, is low in aromatic groups. This deficiency was first indicated from the ultra-violet absorption spectrum of the serum thrombotic accelerator, which revealed a depressed peak at 280 mµ when compared with the corresponding spectrum of serum albumin (Fig. 1).