the implanted coils have detected , in vivo , a three-line spectrum due to a strong concentration of 4-hydroxy- 2,2,6,6-tetramethylpiperidine-1-oxyl free radical ( 'tempol ' ) , a nitroxide spin label , injected either intramuscularly , intraperitoneally or intravenously into the experimental animal immediately prior to the measurement .
C0016693
free radical
C0037914
spin