Figure 4. HPLC profile of radioactive peptides after tryptic digestion of haemoglobin from Fn3k^+/+ and Fn3k^−/− mice phosphorylated with FN3K and [γ-³²P]ATP.

Haemoglobin from Fn3k^+/+ and Fn3k^−/− mice was partially purified on DEAE-Sepharose and incubated with recombinant mouse FN3K and [γ-³²P]ATP for 2 h in vitro. After reduction of fructosamine 3-[³²P]phosphate with NaBH₄, protein was precipitated in acid, resuspended in urea and digested overnight with trypsin [13]. Peptides were separated by reverse-phase HPLC and radioactive peaks were detected by Cerenkov counting.