Interaction of acidic and basic dyes and beef corneal stroma

Acidic and basic dyes react preferentially with the mucoproteins of beef corneal stroma. Free carboxyl groups of the mucoproteins can combine readily with cations; additional reaction with ions seems to involve an unmasking of charged groups in these proteins. Most of the dyes studied apparently react as aggregates in 0.02 M solution, and are fully dissociated only in much more dilute solution. The state of aggregation of methylene blue has a pronounced effect on the affinity with which this dye combines with the tissue, but the chemical reaction is limited, nevertheless, to the corneal mucoproteins.