The synthesis, chemical properties and biological properties of both diazopeptides and N-nitrosopeptides are reviewed. The feasibility of assaying these compounds and studying their formation by Fourier transform infra-red spectroscopy (FTIR) is analysed.
The development of experimental procedures to facilitate kinetic studies of the nitrosation of peptides by FTIR is described. Methods to overcome the principal problems of solvent absorption and the continuous decomposition of the nitrous acid reagent are outlined and tested for the nitrosation of 2-pyrrolidinone as a model substrate.
The infra-red carbonyl bands of N-(N'-acetylglycyl)glycine are unambiguously assigned, via the synthesis and investigation of labelled compounds.
Investigation of the nitrosation of N-(N'-acetylglycyl)glycine by nitrous acid in deuterium chloride is reported. This includes the measurement of reaction rates by FTIR and the identification of products by a combination of FTIR and mass spectroscopy. The kinetic results show that these reactions follow similar mechanisms to those found previously for amide nitrosation. The effect of peptide structure on reactivity towards N-nitrosation is also reported. It is shown that the most important factor influencing reactivity is the accessibility of the peptide N-atom to nitrosation.
The development is described of an FTIR method to measure the formation of diazopeptides. Kinetic studies are reported for the formation of N-(2-diazoacetyl)glycine by the reaction of N-glycylglycine with 2-ethoxyethyl nitrite in aqueous buffers at pH 7.5-11 and 25°C, The results are discussed in terms of possible mechanisms of diazopeptide formation. The effect of structure on diazopeptide reactivity towards diazotisation is also briefly examined and reported
