Our calculations also indicated that the exchange of H to D in the glycyl radical of BSS (in D2O) occurs significantly faster than the reverse exchange of D back to H (after changing D2O back to H2O). This prediction is consistent with the observed complete exchange of H to D in the glycyl radical within the time needed for sample preparation, while the assumed 6.4-fold slower reverse exchange of D to H was apparently still ongoing after the same preparation time.