Proteins end group

Dinitrofluorobenzene (86, X = F) is, because of its reactivity, much used for tagging the NH2 group of terminal amino-acids in protein end group analysis. Once it has reacted with the NH2 it is very difficult to remove again and will thus withstand the subsequent hydrolysis of the protein to its constituent amino-acids. 

Magee, P.S. (2000b) Exploring the potential for allergic contact dermatitis via computed heats of reaction of haptens with protein end-groups. Heats of reaction of haptens with protein end-groups by computation. Quant. Struct. -Act. Relat., 19, 356-365. 

End-group analysis reveals several things. First, it identifies the N- and C-ter-minal residues in the polypeptide chain. Second, it can be a clue to the number of ends in the protein. That is, if the protein consists of two or more different polypeptide chains, then more than one end group may be discovered, alerting the investigator to the presence of multiple polypeptides. 

Fig. 7.17 Bend structure resulting from the HF/4-21G geometry refinement of a type-II bend of N-formyl pentaglycine amide. The torsional angles in this structure are not common in proteins due to the effects of the end groups on the dihedral angles in the bend.

Removal of these end-groups necessary for protein maturation is catalysed by a ferrous peptidase in both cases. The Fe(II) is relatively weakly bound and is a control element of protein maturation... 

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