Chemical Engineering / Analytical Chemistry / Humans / Methylation / Tandem Mass Spectrometry / Sodium Dodecyl Sulfate-Polyacrylamide Gel Electrophoresis / Electrophoresis / Protein isoforms / Amino Acid Sequence / Biochemistry and cell biology / Case Control Studies / Sodium Dodecyl Sulfate-Polyacrylamide Gel Electrophoresis / Electrophoresis / Protein isoforms / Amino Acid Sequence / Biochemistry and cell biology / Case Control Studies