The form of iron which binds specifically to mucins in the Mayer (10) and Hale (2) reactions and their variants appears to be the complex ion FeOH++. The reagent is produced in two ways, the better by carefully computed H2O2 oxidation of ferrous chloride (or acetate in the Mayer reaction), the second by addition of NaOH to FeCl3 solutions, best at a 1:1 M ratio. The first reagent is relatively stable, an 0.1 M solution remaining useful for 4 months; 10 mM solutions of both are usable repeatedly for 4 and 3 weeks, respectively, for the 1st and 2nd variants. The binding of this form of iron is prevented by methylation, impaired variably by acetylation and unaffected by a deamination adequate to prevent anionic dye staining. These characters distinguish FeOH++ sharply from Fe++ and Fe+++ which bind to lysyl and arginyl residues and whose binding is prevented in lysyl areas by both methylation (amine alkylation) and deamination. The action on a number of specific mucosubstances in man and laboratory animals is described. Gastric epithelial mucoprotein is reactive (rat and guinea pig), in distinction from its nonreactivity to most metachromatic basic dyes (7). Reactivity was recorded for guinea pig tracheal cartilage and glands, duodenal goblet cells, Brunner gland mucin, crypt and goblet cell mucins of ileum and colon, for rat mast cells, sublingual and submaxillary but not parotid glands, for human umbilical cord matrix and nucleus pulposus.
Enzymic methylation of arginyl residues in -Gly-Arg-Gly- peptides
