SOLID-STATE C-13-NMR SPECTROSCOPY OF ADDUCTION PRODUCTS OF 2,5-HEXANEDIONE WITH RIBONUCLEASE, ALBUMIN, AND RAT NEUROFILAMENT PROTEIN

The Paal-Knorr condensation reaction between the gamma-diketone 2,5-he xanedione (2,5-HD) and epsilon-amine moieties of proteins of various m olecular weight, including ribonuclease (RNase), bovine serum albumin (BSA) and rat neurofilament (NF), has been investigated by solid-state C-13-NMR spectroscopy. These proteins all reacted with 2,5-HD with th e formation of 2,5-dimethylpyrrole (2,5-DMP) derivatives. The size and complexity of the protein affected the rate of formation of 2,5-DMP d erivatives. Using the selective reducing reagent NaCNBH3, the Paal-Kno rr reaction intermediates were trapped by conversion into amines, whic h were identified by solid-state NMR spectroscopy. The secondary autox idation reaction following the formation of 2,5-DMP derivatives was al so studied by solid-state NMR spectroscopy.