Incorporating the above autoxidation mechanism of 1,4-NQH2 to the coupled enzymatic reduction of 1,4-NQ and H2O2-mediated deprotection of P3 leads to the autocatalytic set depicted in Scheme 3. Furthermore, since P3 is very stable and therefore unlikely to be the source of the nonspecific triggering of autocatalysis, the alternative is to consider it originates from the slow autoxidation of NADH (characterized by the rate kns). In our model, this nonspecific reaction was assumed to be a one-electron transfer process, leading to the release of O2 •-and NAD • (defined as S •-in Scheme 3). Moreover, as we will see later, this reaction is apparently catalyzed by DI (NADPH oxidase-like activity), which leads to a dependence of the nonspecific response on the enzyme concentration. Since there is no available information on the autoxidation kinetics of NADH in the literature (either it is catalyzed or not by DI), the value of kns in our simulations was simply adjusted so that the simulated nonspecific autocatalytic response aligns with the experimental one. In this model, we also substituted the two-electron autoxidation of the intermediate P2 by a one-electron transfer reaction so as to better reflect the radical chain reaction we suspect coupled to this reaction. The S-shaped kinetic curves numerically calculated using the model in Scheme 3 and the associated rate constants gathered in entry 2 of Table are shown in Figure , while the theoretical H2O2 calibration curve derived from these plots is given in Figure (green line). Compared to the previous simulations involving just a simple second order reaction between 1,4-NQH2 and O2, the new computed kinetics traces are now much closer to the experimental ones, a results which highlights the importance to consider the overall complexity of 1,4-NQH2 autoxidation. Interestingly, the discrepancy we observe between simulations and experiments is clearly on the side of the lowest H2O2 concentrations (Figure ), since at the highest concentrations the theoretical plot fits the experimental data almost perfectly. We suspected that this could be related to an inhibition of the autoxidation of P2 intermediate induced by the presence of the reducing enzyme/NADH substrate. As we have already mentioned, the autoxidation reaction mechanism of P2 could well be of a radical nature accompanied by a chain process. If we assume that this is the case, then one can consider that such a radical chain reaction is promoted under oxidizing conditions and inhibited under reducing conditions. To evaluate such an effect on the autocatalysis via simulation, we disabled in our model the autoxidation reaction of the monoboronic intermediate by setting its kn value to zero. Thanks to this, we were able to obtain the magenta simulated plot in Figure , which now predicts the experimental data much more closely. This finding tends to support the hypothesis that the slow self-deprotection of P2 by O2 occurs through a one-electron transfer reaction with concomitant formation of radical species (possibly O2 •-and a naphthoxyl radical), which are then inhibited or scavenged under the reducing conditions (NADH has been shown to efficiently scavenge either HO2 or phenoxyl radicals 57 by one-electron reduction). This also demonstrates that the double masking does not prevent the autocatalytic reaction from working, even when the instability of the monoprotected intermediate is switched-off (i.e. when kn = 0). Indeed, when kn = 0, the autocatalysis still occurs with a reasonable efficiency (magenta curves in Figure ) because, statistically, the probability of having a double-deprotection of the probe is not null, even under the substoichiometric H2O2 conditions used here. In fact, this probability depends directly on the ratio between the first and the second deprotection rate constants (i.e., when the first one is slower than the second, as it is the case here (i.e., 35 vs. 300 M -1 •s -1 , respectively).