Figure 2

Parallel regions of VO²⁺-EPR spectrum of VO²⁺-ADPNP bound to sCD39. a. One mole equivalent of VO²⁺-ADPNP was added to 2.8 mg of sCD39 as described 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 9.40386 GHz, 1000 scans; temperature; 125 K. b. Simulated spectrum was generated by the program QPOWA with the experimental conditions above and A_|| = 504.25 MHz, g_|| = 1.9410 for Species T.