Fraenkel-Conrat

Fraenkel-Conrat H, Brandon BA, Olcott HS. The reaction of formaldehyde with proteins. IV. Participation of indole groups. /. Biol. Chem. 1947 168 99-118. 

Fraenkel-Conrat H, Olcott HS. Reaction of formaldehyde with proteins. VI. Cross-linking of amino groups with phenol, imidazole, or indole groups. J. Biol. Chem. 1948 174 827-843. 

Fraenkel-Conrat H, Olcott H. The reaction of formaldehyde with proteins. V. Crosslinking between amino and primary amide or guanidyl groups. J. Am. Chem. Soc. 1948 70 2673-2684. 

Protein functional groups able to react with anhydrides include the oc-amines at the N-terminals, the s-amine of lysine side chains, cysteine sulfhydryl groups, the phenolate ion of tyrosine residues, and the imidazolyl ring of histidines. However, acylation of cysteine, tyrosine, and histidine side chains forms unstable complexes that are easily reversible to regenerate the original group. Only amine functionalities of proteins are stable to acylation with anhydride reagents (Fraenkel-Conrat, 1959 Smyth, 1967). 

Acetic anhydride is the only monocarboxylic acid anhydride that is important in modification reactions. The acetylation of the amino groups of proteins can be made relatively specific if the reaction is done in saturated sodium acetate, since the o-acetyltyrosine derivative is unstable to an excess of acetate ions (Fraenkel-Conrat, 1959). The tyrosine derivative rapidly hydrolyzes in alkaline reaction conditions, even in the absence of added acetate buffer (Uraki et al., 1957 Smyth, 1967). Treatment with hydroxylamine also cleaves any o-acetyltyrosine modifications, forming acetylhydroxamate, which can be followed by its purple complex with Fe3+ at 540 nm... 

Fraenkel-Conrat, H. (1959) Methods for investigating the essential groups for enzyme activity. In Methods in Enzymology, (S.P. Colowick and N.O. Kaplan, eds.), Vol. 4, pp. 247-269. Academic Press, New York. 

Protein, dcs Tabakmosaik-Virus (und Protein einiger Mutanten) siehe Fraenkel-Conrat 33))... 

Fraenkel-Conrat, H., J. I. Harris, and A. L. Levy Recent developments in techniques for terminal and sequence studies in pe])tides and proteins. In. .Methods of Biochemical Analysis", Vol. 2, 359—425 Ed. D. Click, Interscience Publ., 1955. 

Niu, C. I., and H. Fraenkel-Conrat C-terminal amino acid sequence of tobacco mosaic virus protein. Biochim. Biophys. Acta 16, 597-598 (1955). 

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