Detection of molecular transitions with nitrogen-vacancy centers and electron-spin labels

Abstract We present a protocol that detects molecular conformational changes with two nitroxide electron-spin labels and nitrogen-vacancy (NV) center in diamond. More specifically, we demonstrate the NV can detect energy shifts induced by coupling between labels. The relies on judicious application of microwave radiofrequency pulses range parameters ensures stable resonances. Furthermore, our scheme is optimized using nitroxides distinct nitrogen isotopes. develop simple theoretical model combine Bayesian inference techniques to method enables detection ambient conditions including strong dephasing rates as consequence diamond surface proximity thermalization mechanisms. Finally, counter-intuitively show small residual effect random tumbling becomes resource be exploited extract inter-label distances.