Q-band 2H Mims ENDOR spectra of ReAzS-Trp108 and AzC-Trp48, both in 2H2O, recorded at 20 K and 1.218 T. Microwave pulse lengths 36 ns, rf pulse length 75 μs, τ = 600 ns, repetition time 1 second. Solid: experimental, dashed: simulation. The zero of the frequency offset denotes the 2H Larmor frequency, which is 1/6.511 the 1H Larmor frequency. The asterisk * indicates the 7th harmonic of the 1H spectrum.