Two novel heme-containing peroxidases, one able to incorporate halogens into aromatic substrates and the other able to remove them, have recently been isolated from marine sources and initially ...characterized by Chen et al. (1991) J. Biol. Chem. 266, 23909−23915; (1996) J. Biol. Chem. 271, 4609−4612. The haloperoxidase Notomastus lobatus chloroperoxidase (NCPO) is unusual in requiring a flavoprotein component for peroxidase activity. The dehaloperoxidase (DHP), isolated from Amphitrite ornata, is the only heme-containing peroxide-dependent dehalogenase known to be capable of removing halogens including fluorine. Both enzymes are also quite atypical in that the molecular weights of their heme-containing subunits are less than 16 000, approximately one-half to one-fifth the size of typical heme-containing peroxidases. Interestingly, we have also found that both enzymes are isolated in their oxyferrous states even though all protein purification was done in the absence of any reductant. In the present study, we have examined these two enzymes with magnetic circular dichroism and UV−visible absorption spectroscopy in order to determine the identity of their proximal heme iron ligand. Four derivatives of each enzyme, cyanoferric, deoxyferrous, oxyferrous, and (carbonmonoxy)ferrous, have been examined and spectroscopically compared to parallel derivatives of myoglobin, a well-studied histidine-ligated heme protein. The spectra observed for each derivative of the two new enzymes are very similar to each other and, in turn, to the spectra of the same derivatives of myoglobin. We conclude that both new heme enzymes contain histidine as their proximal heme iron ligand. This makes NCPO the first histidine-ligated heme-containing peroxidase capable of chlorinating halogen acceptor substrates using chloride as the halogen donor. Further, the novel reactivity of DHP is not the result of an unusual proximal ligand. The present results with NCPO and DHP challenge the current dogma of how heme-containing peroxidases function: one chlorinates substrates without having a thiolate proximal ligand, and the other both oxygenates and dehalogenates haloaromatics and yet has a histidine proximal ligand like numerous other peroxidases that are not capable of such a combined reactivity.
The electrochemical conversion of NO x (including NO3 – and NO2 –) to ammonium using renewable energy is emerging as a green alternative pathway for decarbonization of high emission industry to meet ...net zero emission targets. The key to efficient NO x electrolysis relies on the understanding of surface chemistry to establish the structure–activity relationships that will govern future scaleup of this process. In this work, we have undertaken a mechanistic investigation, wherein by tuning the surface oxidation state of CuO x nanoparticles on Cu foam (referred as CuO x /CuF), we are able to investigate its impact on conversion of NO x to ammonium (NH4 +) under acidic reaction conditions. Supported by in situ Raman measurements, we reveal the importance of tuning the Cu oxidation state to maximize Cu2O formation, which forms beneficial Cu2O/Cu interfaces during reaction, allowing an enhanced NH4 + yield with a production rate of 45 nmol s–1 cm–2 and Faradaic efficiency ( FE NH 4 + ) of 83% at −0.5 V vs RHE. Further, we reveal the promising stability of such interfaces under acidic conditions during long-term electrolysis for usage of up to 20 h.
This paper provides an empirical investigation into the international trade and domestic market efficiency effects of physical domestic content requirement in the Australian tobacco leaf growing and ...cigarette manufacturing industries. Our empirical evidence suggests that the content requirement has distorted trade by restricting leaf imports. Nevertheless, the data are also consistent with the efficient contract hypothesis. The mix of domestic to imported leaf used in cigarette manufacturing depends on domestic leaf production costs and on world leaf prices, but not on the negotiated domestic leaf price.
The clinical and histological features of 'mechanic's hands' are described in a patient with polymyositis characterized serologically by antibodies to histidyl tRNA synthetase (Jo-1). Although ...described in the past in association with polymyositis, these distinctive cutaneous lesions have only recently been associated with the 'anti-synthetase syndrome'. It is becoming apparent that recognition of subsets within the spectrum of polymyositis/dermatomyositis characterized by certain clinical and serological features not only have prognostic significance, but also may provide insights into mechanisms of disease.
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