the site of histidine substitution by the 8alpha-methylene of the flavin moiety was shown by methylation of the imidazole ring with methyl iodide , cleavage of the methylhistidine-flavin bond by acid hydrolysis at 150 degrees c , and identification of the methylhistidine isomer by electrophoresis .
C0019602
histidine
C0025780
methylhistidine