STUDY OF THE CONVERSION OF ASPARAGINE AND GLUTAMINE OF PROTEINS INTO DIAMINOPROPIONIC AND DIAMINOBUTYRIC ACIDS USING (BIS(TRIFLUOROACETOXY)IODO)BENZENE PRIOR TO AMINO-ACID DETERMINATION

The treatment of several proteins with [bis(trifluoroacetoxy)iodobenze (BTI) was examined as a possible way to determine separately their asparagine and glutamine content, through the quantification of their corresponding 2,3-diaminopropionic and 2,4-diaminobutyric acids. The diamino acid peaks were resolved between those of phenylalanine and lysine after a modification of the chromatographic conditions required for phenylthiocarbamylamino acid analysis. Rate studies performed on three proteins with BTI in the presence of dimethylformamide at 60-degrees-C showed a maximum conversion of amides into diamino acids ranging from 50 to 83% after 4 h of contact, thereby making the direct quantification of amides in protein through the evaluation of diamino acids unsuitable; a fast (30 min) and virtually complete disappearance of glutamine; and a slower (2 h) and only partial (65 +/- 6%) disappearance of asparagine.