APOE and pancreatitis: MALDI-TOF-MS analysis identified the protein detected in spots 1 to 4 as the AAT precursor and spots 6, 7, 8, and 17 as apolipoprotein E. These proteins, which had identical molecular weight, but different pI, were found to be significantly lower in the HSAP group than in the NHSAP group at 6 h after surgical induction of pancreatitis (Fig. 2c).