Figure 5

Parallel regions of VO²⁺-EPR spectrum of VO²⁺-ATP bound to sCD39. a. One mole equivalent of VO²⁺-ATP was added to 5.7 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 9.40658 GHz, 3000 scans; temperature; 125 K. b. Simulated spectrum was generated by the program QPOWA with the experimental conditions above and A_|| = 489.5 MHz, g_|| = 1.9455 for Species D2.