METACHROMATIC PROPERTIES OF AMYLOID IN SOLUTION

The chromotropic properties of water-soluble amyloid are quantitatively studied in solution with the metachromatic dyes, crystal violet and toluidine blue and compared with the properties of chondroitin sulfate of bovine nasal cartilage. The stabilities of the metachromatic compounds are measured in terms of the ethanol concentration required to cause the return of the depressed α band to half its peak value in water alone. The metachromatic properties of amyloid stand in sharp contrast to those of chondroitin sulfate: amyloid compounds of toluidine blue and crystal violet are about equally stable, but the chondroitin sulfate compound with toluidine blue is far more stable than either, and the chondroitin sulfate compound with crystal violet is far less stable than either. An attempt to measure the equivalent weight of amyloid by studying the depression of the α band of each of these dyes, as well as of acridine orange, as a function of amyloid concentration gave values of 7000, 6000 and 3000 for three different preparations.