RELATION OF MELANOMA HOMOGENATE AND ASCORBATE SOLUTION ELECTRON PARAMAGNETIC RESONANCE DOUBLETS

The electron parameagnetic resonance spectroscopy (EPR) doublet free radical signal observed in S-91 mouse melanoma cleared sucrose homogenates was compared with the doublet signal observed in ascorbate solutions. The two doublets have very similar g-values, hyperfine splitting constants, line widths, and behavior toward a number of chemical and physical agents. After centrifugation adequate to remove mitochondria and melanosomes the signal is observed in the supernatant fluid. The melanoma homogenate EPR doublet is tentatively identified as being due to ascorbyl free radical. Melanoma tissue contains 16-22 mg/100 gm ascorbic acid. Ascorbate does not selectively inhibit the growth of melanoma in vitro. The ascorbyl radical may have biomedical significance. © 1968.