Figure 6

Parallel regions of VO²⁺-EPR spectrum of free VO²⁺ bound to sCD39. a. One mole equivalent of free VO²⁺ was added to 2.6 mg of sCD39 prepared as in Experimental Procedures. EPR conditions were as follows: field modulation frequency, 100 kHz; modulation amplitude, 0.97 G; receive gain, 2 × 10⁴; sweep time 5.243 s; time constant 1.28 ms; micropower, 1.0 mW; microwave frequency 9.40798 GHz, 3000 scans; temperature; 125 K. b. Simulated spectrum was generated by the program QPOWA with the experimental conditions above and A_|| = 486.00 MHz, g_|| = 1.9460 for Species V.