Dinitrophenylamino acid

The major products of photolysis at pH 8 of a series of A-sub-stituted 2,4-dinitrophenylamino acids of general formula 378 are 4-nitro-2-nitrosoaniline (379), the aldehyde (380), and carbon dioxide399,400 the formation of the nitroso function may well be... 

Table II. Chiroptical Properties of Various 2,4-Dinitrophenylamino Acid Derivatives"... 

The TLC method was developed for amino acids therefore, in principle, it is equally applicable to peptides. Peptides, such as amino acids, are generally hydrophilic. There are, however, limits to this analogy. Dinitrophenylamino acid derivatives (DNP amino acids) and phenylthiohydantoin derivatives (PTH amino acids) are obtained when reaction of peptides or proteins with dinitrofluorobenzene or phenyl mustards are properly degraded. Their separation from reaction mixtures and their identification are considerable practical importance because they constitute essential steps... 

Strong attachment to polyamides is encountered with numerous nitro compounds. The addition of nitro compounds to a polyamide corresponds to the reaction of a Lewis acid with a base separation of aromatic nitro compounds on polyamide can thus be regarded as ion exchange [293]. Elution with sharp zones is thus possible only with buffering solvents. A successful separation of dinitrophenylamino acids, arising from the determination of the amino end-groups of peptides and proteins, has been possible on polyamide colunms [293, 697]. 

Dinitrophenylamino acids (DNP-amino acids) and phenylthio-hydantoins (PTH-amino acids) are formed when proteins or peptides are treated with dinitrofluorobenzene [151—154] or phenyl isothiocyanate [155], respectively, and the reaction product suitably broken down. Their separation from the reaction mixture and their identification is of considerable practical importance since systematic application enables sequence analysis of peptide structures to be performed. Numerous investigators have worked on this problem... 

The formation of dinitrophenylamino acids (DNP-amino acids), as mentioned above, is portrayed in the reaction scheme below. 

The labeling group is retained during hydrolysis. Along with all the other amino acids one dinitrophenylamino acid is obtained which, of course, originally was the one with a free amino group, i.e. the N-terminal amino acid It is. identified easily. 

An aldoxime and a suitably positioned 2,4-dinitrophenylamino group react in hot acid with elimination of 2,4-dinitroaniline and the formation of an isoquinoline 2-oxide in high yield. 

It is of equal importance to ascertain the sequence of amino acids in naturally occurring peptides as in peptides found in protein hydrolyzates (cf. Chapt. IV-2). The methods can be indicated only briefly. Terminal amino groups are allowed to react with fluorodinitrobenzene. Hydrolysis frees the characteristically yellow dinitrophenylamino compounds (Sanger). 

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