Abstract The use of 13 C NMR for the identification of the site of cross-linking of amino acids by formaldehyde has been evaluated by use of model compounds, such as 2, 4- dimethylphenol for tyrosine. The 13 C chemical shifts of the formaldehyde-derived methylene carbons occur within the range 50-60 ppm downfield from Me 4 Si. Estimated shifts in lysine-lysine and tyrosine-glutamine cross-linked systems fall just outside this ...
