Ji-Hu Su

Naphthalene (Nap) is widely distributed in the environment and has attracted concern due to its recalcitrance to biodegradation and acute toxic effects. Although several laccases can degrade naphthalene, it remains unclear whether laccase is involved in dioxygenation or ring fission of polycyclic aromatic hydrocarbons (PAHs). We demonstrated that laccase has a naphthalene dioxygenase function with a distinct joint approach to oxygen and the alternative regioselective ring-fission process. These results supplement the family of dioxygenase with laccase, a mild method for the ring opening of aromatics, and an operable scale-up application for remediation from PAH pollution and for regioselective oxygenation and ring opening.

The existence of the magnetic isotope effect in chemical reactions has been recognized for decades. However, its critical significance in influencing chemical processes remains to be substantiated, primarily due to its seemingly minor thermodynamic contributions and its coexistence with mass-dependent isotope effects. In this study, we unequivocally demonstrate that the oxidation of Ni2+ to Ni3+ in a nickel complex can be entirely governed by the 61Ni isotope, despite its low natural abundance. Our findings reveal that such remarkable selectivity is achieved through a careful balance of the kinetics involved in the reaction processes; notably, a well-designed complex with appropriate confinement of the reaction center plays an essential role. These results challenge traditional paradigms in chemistry and pave the way for numerous significant applications.

A biomimetic catalytic approach for the aerobic oxidation of C–sp(3)–H bonds using galactose oxidase model compound was developed. EPR showed that the Cu^I-radical intermediate species was critical for O₂ activation.

The Ni_d site coordination microenvironment of a truncated acetyl-coenzyme A synthase has been designed systematically for functional conversion to a Ni-SOD-like enzyme. To this end, the first strategy is to introduce an axial histidine ligand, using mutations F598H, S594H and S594H-GP individually. The resulting three mutants obtained Ni-SOD-like activity successfully, although the catalytic activity was about 10-fold lower than in native Ni-SOD. The second strategy is to mimic the H-bond network in the second sphere coordination microenvironment of the native Ni-SOD. Two mutations based on F598H (EFG-F598H and YGP-F598H) were designed. The successful EFG-F598H exhibited ~3-fold Ni-SOD-like activity of F598H. These designed Ni-SOD-like metalloproteins were characterized by UV/Vis, EPR and Cyclic voltammetry while F598H was also characterized by X-ray protein crystallography. The pH titrations were performed to reveal the source of the two protons required for forming H₂O₂ in the SOD catalytic reaction. Based on all of the results, a proposed catalytic mechanism for the Ni-SOD-like metalloproteins is presented.

Poly(vinylidene fluoride-chlorotrifluoroethylene) (P(VDF-CTFE)) membranes were prepared by drop-casting with tetrahydrofuran (THF), and were then radiated by a low dose of gamma radiation without any other reagents. The apparent colour of the freshly prepared film was a semi-transparent white, which gradually darkened and finally turned black after 10.2 kGy gamma radiation. Meanwhile, the yield and breaking strength of the membrane both improved. X-Ray diffraction (XRD) spectra showed that the structure of the microcrystal of the irradiated P(VDF-CTFE)-THF membrane was not changed. FT-IR analysis showed that the structure of the newly formed double bonds was dominated by –CF2–CF=CH–CF2–, which was formed by both dehydrofluorination and dehydrochlorination. This structure was further confirmed by 1H NMR spectra. The intermediates, such a radical-containing double bonds (–(CF=CH)n–C•F–) formed in this process were traced by electron paramagnetic resonance (EPR) spectroscopy. The thermal and mechanical properties were studied by gel permeation chromatography (GPC), thermogravimetric analysis (TGA), stress–strain and dynamic mechanical analysis (DMA), and all the changes of microstructure and optimization of apparent properties were not found in the corresponding membrane prepared by a solution-cast method with ethyl acetate (EtOAc). Therefore, this paper briefly analyses the probable mechanism of using low dose of gamma radiation to improve the mechanical properties of the P(VDF-CTFE) film prepared with THF.

The formation and qualification of redox sites in transition metal oxides are always the active fields related to electronics, catalysis, sensors, and energy-storage units. In the present study, the temperature dependence of thermal reduction of MoO₃ was surveyed at the range of 350 °C to 750 °C. Upon reduction, the formed redox species characterized by EPR spectroscopy are the Mo^V ion and superoxide anion radical (O₂⁻) when the reduction was induced at the optimal temperature of 300−350 °C. When heating-up from 350 °C, the EPR signals started to decline in amplitude. The signals in the range of 400−450 °C decreased to half of that at 350 °C, and then to zero at ∼600 °C. Further treatment at even higher temperature or prolonged heating time at 500 °C caused more reduction and more free electrons were released to the MoO₃ bulk, which results in a delocalized means similar to the anti-ferromagnetic coupling. These data herein are helpful to prepare and study the metal-oxide catalysts.

The design of functional metallohydrogels is attractive but challenging. A rational approach is introduced for designing functional metallohydrogels using chiral ligands, a phenylalanine derivative with a pyridyl group (l/d‐PF). Intriguingly, the as‐prepared metallohydrogel exhibits excellent O₂ binding and activating properties. Insights into the O₂ binding pathway reveals the presence of a novel [(l+d)‐PF‐Cu³⁺‐O₂⁻] species, which can efficiently reduce ferric cytochrome c with the reactive O₂⁻ by receiving an electron from reductant ascorbic acid. This study provides helpful instructions for developing new artificial systems with specific functions through the effective combination of chiral ligands with metal ions.

The design of functional metallohydrogels is attractive but challenging. A rational approach is introduced for designing functional metallohydrogels using chiral ligands, a phenylalanine derivative with a pyridyl group (l/d‐PF). Intriguingly, the as‐prepared metallohydrogel exhibits excellent O₂ binding and activating properties. Insights into the O₂ binding pathway reveals the presence of a novel [(l+d)‐PF‐Cu³⁺‐O₂⁻] species, which can efficiently reduce ferric cytochrome c with the reactive O₂⁻ by receiving an electron from reductant ascorbic acid. This study provides helpful instructions for developing new artificial systems with specific functions through the effective combination of chiral ligands with metal ions.