MAGNETIC FIELD IN GAUSS

We have recently demonstrated an EPR signal in spinach ferredoxin on reduction either enzymically or with dithionite (Palmer and Sands, 1966). It is the purpose of this communication to report on the EPR spectrum found in the ferredoxin obtained from the bacterium C. pasteurianum. The ferredoxin was purified by the method of Mortenson (1964) and had an absorbancy ratio 285 rnp; 3QO rnF of 0.82. 2, it was pure by disc electrophoresis on polyacrylamide at pH 9.0. The oxidised enzyme exhibits a small and variable resonance at g = 2.0. This signal is typical of high spin ferric ion in a weak crystal field. On reduction with dithionite the EPR signal shown in Fig. 1 is obtained. The apparent g-values are gx = 1.89,,