Nitrile hydratase (NHase) is one of a growing number of enzymes shown to contain posttranslationally modified cysteine sulfenic acids (Cys-SOH). Cysteine sulfenic acids have been shown to play diverse roles in cellular processes, including transcriptional regulation, signal transduction, and the regulation of oxygen metabolism and oxidative stress responses. The function of the cysteine sulfenic acid coordinated to the iron active site of NHase is unknown. Herein we report the first example of a sulfenate-ligated iron complex, [Fe III (ADIT)(ADIT-O)] + (5), and compare its electronic and magnetic properties with those of structurally related complexes in which the sulfur oxidation state and protonation state have been systematically altered. Oxygen atom addition was found to decrease the unmodified thiolate Fe-S bond length and blue-shift the ligand-to-metal charge-transfer band (without loss of intensity). S K-edge X-ray absorption spectroscopy and density functional theory calculations show that, although the modified RS-O − fragment is incapable of forming a π bond with the Fe III center, the unmodified thiolate compensates for this loss of π bonding by increasing its covalent bond strength. The redox potential shifts only slightly (75 mV), and the magnetic properties are not affected (the S = ½ spin state is maintained). The coordinated sulfenate S-O bond is activated and fairly polarized (S + -O − ). Addition of strong acids at low temperatures results in the reversible protonation of sulfenateligated 5. An X-ray structure demonstrates that Zn 2+ binds to the sulfenate oxygen to afford [Fe III HHS Public Access Author Manuscript Author ManuscriptAuthor ManuscriptAuthor Manuscript unmodified NHase thiolate, involving its ability to "tune" the electronics in response to protonation of the sulfenate (RS-O − ) oxygen and/or substrate binding, is discussed.Nitrile hydratases (NHases) are non-heme iron enzymes that convert nitriles to less toxic amides cleanly, and rapidly, under mild conditions. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] It is unusual for a hydrolytic metalloenzyme to incorporate iron, as opposed to zinc, 17,18 presumably because, unlike other metal ions, Zn 2+ is not complicated by redox chemistry. Iron, on the other hand, can promote unwanted side reactions with dioxygen (i.e., Fenton chemistry involving OH · radicals) upon reduction to the Fe 2+ oxidation state. 19,20 The NHase iron site is, however, redox inactive and stabilized in the 3+ oxidation state. The stabilization of Fe 3+ is accomplished by placing the iron in an electron-rich environment consisting of five anionic ligands-two deprotonated peptide amides and three cysteinates (Figure 1). Two of the three coordinated cysteinate sulfurs are oxidized (post-translationally modified) in NHase -one to a sulfenic acid ( 114 Cys-S-(OH)) and the other to a sulfinate 112 CysSO 2 −.3,21 The third cysteinate sulfur, which is trans to the inhibitor/substrate binding site and less accessible to solvent, remains unmodifie...

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Quasi-solid-state Zn-air batteries are usually limited to relatively low-rate ability (<10 mA cm−2), which is caused in part by sluggish oxygen electrocatalysis and unstable electrochemical interfaces. Here we present a high-rate and robust quasi-solid-state Zn-air battery enabled by atomically dispersed cobalt sites anchored on wrinkled nitrogen doped graphene as the air cathode and a polyacrylamide organohydrogel electrolyte with its hydrogen-bond network modified by the addition of dimethyl sulfoxide. This design enables a cycling current density of 100 mA cm−2 over 50 h at 25 °C. A low-temperature cycling stability of over 300 h (at 0.5 mA cm−2) with over 90% capacity retention at −60 °C and a broad temperature adaptability (−60 to 60 °C) are also demonstrated.

It is widely accepted that photogenerated holes are the only driving force for oxidizing an electron donor to form H+ during photocatalytic H2O2 production (PHP). Here, we use nitrogen deficiency carbon nitride as a model catalyst and propose several different reaction mechanisms of PHP based on the comprehensive analysis of experiment and simulation results. Nitrogen vacancies can serve as a center for oxidation, reduction, and charge recombination, promoting the generation of h+, •O2 –, and 1O2, respectively, and thus induce H2O2 generation through five different pathways. In particular, the 1O2 anchored on the catalyst surface can realize the indirect oxidation of isopropanol with the assistance of surrounding water molecules and produce H2O2 with the lowest barrier. This work proves that H2O2 can be generated through multiple pathways and highlights the main roles of 1O2, which are ignored by previous studies.

In-doped ZnO (IZO) nanowires have been synthesized by a thermal evaporation method. The morphology and microstructure of the IZO nanowires have been extensively investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), and high-resolution transmission electron microscopy (HRTEM). The products in general contain several kinds of nanowires. In this work, a remarkable type of IZO zigzag nanowire with a periodical twinning structure has been investigated by transmission electron microscopy (TEM). HRTEM observation reveals that this type of IZO nanowire has an uncommonly observed zinc blend crystal structure. These nanowires, with a diameter about 100 nm, grow along the [111] direction with a well-defined twinning relationship and a well-coherent lattice across the boundary. In addition, an IZO nanodendrite structure was also observed in our work. A growth model based on the vapor-liquid-solid mechanism is proposed for interpreting the growth of zigzag nanowires in our work. Due to the heavy doping of In, the emission peak in photoluminescence spectra has red-shifted as well as broadened seriously.

Fullerene-based organic solar cells with only a minute amount of donor show a substantial photocurrent while maintaining a large open-circuit voltage. At low concentrations the donor is fully dispersed within the fullerene and no percolation pathways of holes toward the anode exist; this morphology is in contrast to bulk-heterojunction donor:acceptor blends where percolation pathways for both electrons and holes are present within their respective transport phases. Therefore, the question of how holes contribute to the photocurrent arises. Here we demonstrate that the photocurrent is readily explained by photogenerated holes transferring back to the fullerene matrix due to Coulomb repulsion and the fullerene acting as an ambipolar conductor for both electrons and holes. The two critical parameters controlling this process are the values of the highest occupied molecular orbital level difference between the donor and the acceptor and of the recombination strength; both are found to agree between experimental measurements and kinetic Monte Carlo simulations. We provide evidence that the highest occupied molecular orbital level difference between donor and acceptor is smaller in a dilute donor configuration. Successive percolation pathways toward the contactsthe reason for introducing the bulk-heterojunction configurationare not an absolute requirement to obtain substantial photocurrents in organic solar cells.

p-Type metal-oxide hole transport layer (HTL) suppresses recombination at the anode and hence improves the organic photovoltaic (OPV) device performance. While NiOx has been shown to exhibit good HTL performance, very thin films (<10 nm) are needed due to its poor conductivity and high absorption. To overcome these limitations, we utilize CuGaO2, a p-type transparent conducting oxide, as HTL for OPV devices. Pure delafossite phase CuGaO2 nanoplates are synthesized via microwave-assisted hydrothermal reaction in a significantly shorter reaction time compared to via conventional heating. A thick CuGaO2 HTL (∼280 nm) in poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) devices achieves 3.2% power conversion efficiency, on par with devices made with standard HTL materials. Such a thick CuGaO2 HTL is more compatible with large-area and high-volume printing process.

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