Nitromalondialdehyde reaction with arginine

Nitromalondialdehyde reaction with arginine The products formed by nitromalondialdehyde have been characterized (Signor et al. 1971). Thus N-acetylarginine reacts with nitromalondialdehyde to yield a nitropyrimidine derivative as indicated below in eq. (3.2.). 

Since the optimum pH range for the reaction is between pH 12 and 14, the usefulness of nitromalondialdehyde is restricted to denatured proteins. 

To modify the S-carboxymethylated B chain of insulin. Signor et al. (1971) added about 3.0 mmoles of the peptide dissolved in 1.0 ml of 1 M NaOH to 1 ml of water containing 10 mg of nitromalondialdehyde (70 mmoles). After 2 hr at 0-5°C excess modification reagent was removed by gel filtration using 50% formic acid as eluent. 

Arginine residues modified by nitromalondialdehyde are resistant to tryptic digestion. However, reduction of the derivative by sodium borohydride yields tetrahydropyrimidyl compounds which are susceptible to hydrolysis by trypsin. Modification by nitromalondialdehyde thereby permits the restriction of tryptic digestion to lysine 

The two reactions most commonly employed for the modification of protein carboxyl groups have been acid-catalyzed esterification (Wilcox 1967), and coupling with nucleophiles mediated by a water-soluble carbodiimide. The latter reaction has been exploited widely in the determination of the carboxyl group content of proteins as well as in studies of carboxyl group function, and would at present appear to be the reaction of choice for these purposes. 

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