Chemical heterogeneity of structural proteins of cancers with a common low electron spin resonance signal.

Electron spin resonance measurements are presented for the separated structural and soluble components of a variety of both normal and cancerous tissues. The signal at g = 2 from the structural part of the normal tissues was at least an order of magnitude stronger than the corresponding signal from the structural part of the cancers. In contrast, no significant difference in radical concentration was found between the soluble fractions of normal and cancerous tissues. Despite their common low signal at g = 2, the structural cancer fractions displayed a remarkable chemical heterogeneity. An important finding was that even cancers of the same histology reacted differently from one another when treated with a variety of chemical probes.