Cross-linking of amino acids by formaldehyde. Preparation and 13C NMR spectra of model compounds.
Model cross-linked systems have been prepared by reacting amino acids or alkylamines with formaldehyde and various amino acid model compounds such as 2,4-dimethylphenol (tyrosine), 3-methylindole (tryptophan) and alkylamides (glutamine, asparagine. 13C NMR spectra of the products show the resonances of the formaldehyde-derived methylene carbons in the region 45-60 ppm. Interferences occur from resonances of the alpha-amino acid methine carbons. From the data for these products and other model compounds it has been possible to predict the shifts of the residual methylene carbons in a variety of cross-linked systems. This NMR technique shows promise as a rapid non-degradative method for identification of cross-linking sites.
D000596:Amino Acids; D055598:Chemical Phenomena; D002621:Chemistry; D005557:Formaldehyde; D005973:Glutamine; D008239:Lysine; D009682:Magnetic Resonance Spectroscopy; D008954:Models, Biological; D008968:Molecular Conformation; D008970:Molecular Weight; D010455:Peptides; D011487:Protein Conformation; D014364:Tryptophan
D000596:Amino Acids; D010455:Peptides; D005973:Glutamine; D005557:Formaldehyde; D014364:Tryptophan; D008239:Lysine