The CuICuICuI tricopper cluster complex is the only known catalyst capable of efficient methane oxidation near room temperature similar to the particulate methane monooxygenase (pMMO). Here, we compare the turnover of the CuICuICuI tricopper catalyst with the biochemistry of the functional pMMO. Insights into the turnover of the biomimetic tricopper catalyst are derived from anaerobic electrospray mass spectrometry (ESI‐MS) and high‐resolution ESI‐MS (HR‐ESI‐MS). We follow activation of the tricopper cluster with O2/H2O2 by rapid‐freeze‐quench ESI‐MS, high‐resolution cold‐spray ionization mass spectrometry (HR‐CSI‐MS) and electron paramagnetic resonance spectroscopy, capturing all the species participating in the activation and deactivation pathways of the turnover cycle. The reactivity of the activated tricopper complex toward alkane oxidation is essentially the same as the biochemistry reported earlier for pMMO from Methylococcus capsulatus (Bath).

Saddle-shaped hemes have been discovered in the structures of most peroxidases. How such a macrocycle deformation affects the reaction of Fe III hemes with hydrogen peroxide (H 2 O 2 ) to form high-valent Fe-oxo species remains uncertain. Through examination of the ESI-MS spectra, absorption changes and 1 H NMR chemical shifts, we investigated the reactions of two Fe III porphyrins with different degrees of saddling deformation, namely Fe III (OETPP)ClO 4 (1 OE ) and Fe III (OMTPP)ClO 4 (1 OM ), with tert-butyl hydroperoxide (tBuOOH) in CH 2 Cl 2 at À 40 °C, which quickly resulted in OÀ O bond homolysis from a highly unstable Fe III -alkylperoxo intermediate, Fe III -O(H)OR (2) into Fe IV -oxo porphyrins (3).Insight into the reaction mechanism was obtained from [tBuOOH]-dependent kinetics. At À 40 °C, the reaction of 1 OE with tBuOOH exhibited an equilibrium constant (K a = 362.3 M À 1 ) and rate constant (k = 1.87 × 10 À 2 s MÀ > 1 ) for the homolytic cleavage of the 2 OÀ O bond that were 2.1 and 1.4 times higher, respectively, than those exhibited by 1 OM (K a = 171.8 M À 1 and k = 1.36 × 10 À 2 s À 1 ). DFT calculations indicated that an Fe III porphyrin with greater saddling deformation can achieve a higher HOMO ([Fe(d z 2 ,d x 2 À y 2 )-porphyrin(a 2u )]) to strengthen the orbital interaction with the LUMO (OÀ O bond σ*) to facilitate OÀ O cleavage.

We consider a three-species predator-prey system involving two competing predators and one prey. The species diffuse with nonlocal dispersal kernels with possibly non-compact support, and they interact in a heterogeneous environment moving with a positive forced speed such that the environment is favorable to the prey in the absence of predators far ahead of the shifting boundary and it is unfavorable far behind. Such systems arise in the modeling of population dynamics under the effect of a shifting environment, such as climate change. We show on the one hand the existence of waves connecting the trivial state to the unique constant positive co-existence state for any value of the forced speed. On the other hand, we show the existence of critical positive speeds for the existence of waves connecting the trivial state to the states corresponding to the absence of one or two predators.