35-GHz Davies pulsed-ENDOR of Fe(II)ACCO⋅NO. Trace A, with natural-abundance ACC (g1 = 4.23). Trace B, with natural-abundance dl-alanine (g1 = 4.23). Trace C, with 15N-substituted dl-alanine (g1 = 4.23). Trace D, C − B difference spectrum. Trace E, C − A difference spectrum. Trace F, with natural-abundance dl-alanine (g2 = 3.82). Trace G, with 17O-substituted dl-alanine (g2 = 3.82). Conditions: T = 2 K, νMW = 34.72 GHz, MW pulse lengths = 80, 40, and 80 ns, RF pulse length = 60 μs, repetition rate = 50 Hz. Each spectrum consists of 256 points, with each point an average of 1,000 transients.