STUDIES OF DEHYDROGENASE MECHANISMS USING ADP-TETRAMETHYLPIPERIDINE-1-OXYL (ADP-R.), A PARAMAGNETIC ANALOG OF NAD††This work was supported in part by U.S.P.H.S. grants AM-13351, CA-06927 and RR-05539 from the National Institutes of Health, National Science Foundation grant GB-8579, American Cancer Society grant IN-49, and by an appropriation from the Commonwealth of Pennsylvania.