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651.
Halasz A Manno D Perreault NN Sabbadin F Bruce NC Hawari J 《Environmental science & technology》2012,46(13):7245-7251
Anaerobic transformation of the explosive RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine) by microorganisms involves sequential reduction of N-NO(2) to the corresponding N-NO groups resulting in the initial formation of MNX (hexahydro-1-nitroso-3,5-dinitro-1,3,5-triazine). MNX is further reduced to the dinitroso (DNX) and trinitroso (TNX) derivatives. In this paper, we describe the degradation of MNX and TNX by the unusual cytochrome P450 XplA that mediates metabolism of RDX in Rhodococcus rhodochrous strain 11Y. XplA is known to degrade RDX under aerobic and anaerobic conditions, and, in the present study, was found able to degrade MNX to give similar products distribution including NO(2)(-), NO(3)(-), N(2)O, and HCHO but with varying stoichiometric ratio, that is, 2.06, 0.33, 0.33, 1.18, and 1.52, 0.15, 1.04, 2.06, respectively. In addition, the ring cleavage product 4-nitro-2,4,-diazabutanal (NDAB) and a trace amount of another intermediate with a [M-H](-) at 102 Da, identified as ONNHCH(2)NHCHO (NO-NDAB), were detected mostly under aerobic conditions. Interestingly, degradation of TNX was observed only under anaerobic conditions in the presence of RDX and/or MNX. When we incubated RDX and its nitroso derivatives with XplA, we found that successive replacement of N-NO(2) by N-NO slowed the removal rate of the chemicals with degradation rates in the order RDX > MNX > DNX, suggesting that denitration was mainly responsible for initiating cyclic nitroamines degradation by XplA. This study revealed that XplA preferentially cleaved the N-NO(2) over the N-NO linkages, but could nevertheless degrade all three nitroso derivatives, demonstrating the potential for complete RDX removal in explosives-contaminated sites. 相似文献
652.
NL Rose VJ Jones PE Noon DA Hodgson RJ Flower PG Appleby 《Environmental science & technology》2012,46(18):9881-9889
(210)Pb-dated sediment cores taken from lakes on the Falkland Islands, the South Orkney Islands, and the Larsemann Hills in Antarctica were analyzed for fly ash particles to assess the temporal record of contamination from high temperature fossil-fuel combustion sources. Very low, but detectable, levels were observed in the Antarctic lakes. In the Falkland Island lakes, the record of fly ash extended back to the late-19th century and the scale of contamination was considerably higher. These data, in combination with meteorological, modeling, and fossil-fuel consumption data, indicate most likely sources are in South America, probably Chile and Brazil. Other southern hemisphere sources, notably from Australia, contribute to a background contamination and were more important historically. Comparing southern polar data with the equivalent from the northern hemisphere emphasizes the difference in contamination of the two circumpolar regions, with the Falkland Island sites only having a level of contamination similar to that of northern Svalbard. 相似文献
653.
Boxin Ou Kristen N. Bosak Paula R. Brickner Dominic G. Iezzoni E. Mitchell Seymour 《Journal of food science》2012,77(5):H105-H112
Abstract: Processing of fruits and vegetables affects their phytochemical and nutrient content. Tart cherries are commercially promoted to possess antioxidant and anti‐inflammatory activity. However, processing affects their phytochemical content and may affect their related health benefits. The current study compares the in vitro antioxidant capacity and anti‐inflammatory cyclooxygenase activity of processed tart cherry (Prunus cerasus) products—cherry juice concentrate, individually quick‐frozen cherries, canned cherries, and dried cherries. Cherry products were analyzed for total anthocyanin and proanthocyanidin content and profile. On a per serving basis, total anthocyanins were highest in frozen cherries and total proanthocyanidins were highest in juice concentrate. Total phenolics were highest in juice concentrate. Juice concentrate had the highest oxygen radical absorbance capacity (ORAC) and peroxynitrite radical averting capacity (NORAC). Dried cherries had the highest hydroxyl radical averting capacity (HORAC) and superoxide radical averting capacity (SORAC). Processed tart cherry products compared very favorably to the U.S. Dept. of Agriculture‐reported ORAC of other fresh and processed fruits. Inhibition of in vitro inflammatory COX‐1 activity was greatest in juice concentrate. In summary, all processed tart cherry products possessed antioxidant and anti‐inflammatory activity, but processing differentially affected phytochemical content and in vitro bioactivity. On a per serving basis, juice concentrate was superior to other tart cherry products. Practical Application: Processing of fruits and vegetables affects their chemical and nutrient content and perhaps their related health benefits. Comparative studies are valuable to ascertain the effects of processing on fruit and vegetable chemical content and bioactivity. Here we present tart cherries as a model for this type of detailed comparison. 相似文献
654.
Eating is a dynamic experience, and temporal sensory methods have been proposed to document how products change over the course of consumption or use (nonfood). A search of online databases yielded approximately 170 sources related to temporal evaluation of food products that were compiled and reviewed. This review summarizes the evolution of temporal methodologies (past), offers guidance in selecting appropriate methods (present), and provides insights into the future of temporal methodologies in the sensory space. Temporal methods have evolved to document a variety of characteristics in food products including how the intensity of a specific attribute changes over time (Time–Intensity), which specific attribute is dominant at each time during evaluation (Temporal Dominance of Sensations), which attributes are present at each time point during evaluation (Temporal Check-All-That-Apply), and many others (Temporal Order of Sensations, Attack–Evolution–Finish, and Temporal Ranking). In addition to documenting the evolution of temporal methods, this review considers the selection of an appropriate temporal method based on the objective and scope of research. When choosing a temporal method, researchers should also consider the selection of panelists to perform the temporal evaluation. Future temporal research should focus on validation of new temporal methods and explore how methods can be implemented and improved to add to the usefulness of temporal techniques for researchers. 相似文献
655.
Dominic G. Whittaker Jiahui Wang Joseph G. Shuttleworth Ravichandra Venkateshappa Jacob M. Kemp Thomas W. Claydon Gary R. Mirams 《Journal of the Royal Society Interface》2022,19(193)
Mathematical models of voltage-gated ion channels are used in basic research, industrial and clinical settings. These models range in complexity, but typically contain numerous variables representing the proportion of channels in a given state, and parameters describing the voltage-dependent rates of transition between states. An open problem is selecting the appropriate degree of complexity and structure for an ion channel model given data availability. Here, we simplify a model of the cardiac human Ether-à-go-go related gene (hERG) potassium ion channel, which carries cardiac IKr, using the manifold boundary approximation method (MBAM). The MBAM approximates high-dimensional model-output manifolds by reduced models describing their boundaries, resulting in models with fewer parameters (and often variables). We produced a series of models of reducing complexity starting from an established five-state hERG model with 15 parameters. Models with up to three fewer states and eight fewer parameters were shown to retain much of the predictive capability of the full model and were validated using experimental hERG1a data collected in HEK293 cells at 37°C. The method provides a way to simplify complex models of ion channels that improves parameter identifiability and will aid in future model development. 相似文献
656.
Dominic Bartels Andrea von Lattre-Hertel Tobias Novotny Andreas Mohr Horst Hill Carsten Merklein Michael Schmidt 《国际钢铁研究》2023,94(8):2200925
Low-alloyed steels are used for a variety of different applications like bearings or gears. Additive manufacturing technologies like directed energy deposition (DED-LB/M) allow for a fast and close-to-contour fabrication of sophisticated products without excessive waste of material. However, the DED-LB/M process cannot be considered as state-of-the-art for this group of materials. This study presents findings on the material properties of the additively manufactured low-alloyed steel Bainidur AM by means of DED-LB/M. This includes studies on the mechanical properties (hardness, compression strength) as well as the microstructural properties (scanning electron microscopy [SEM]). The microstructure in the as-built state appears like a bainitic–martensitic one with shares of retained austenite which is not fully transformed during cooling. As a differentiation is barely possible from the SEM images, a plethora of investigations is further used to assess the microstructure. As-built samples possess a good combination of ductility and hardness. Furthermore, the specimens are characterized by a good tempering stability up to 600 °C. This tempering stability is characterized by a homogeneous hardness of around 400 HV1 for all temperatures. In contrast, the conventionally hardened specimens show a drop-off in material hardness, further indicating the excellent material properties of additively manufactured Bainidur AM. 相似文献
657.
Chew Yick Eu Gan Zheng Wei Heng Herman Nair Purusothmn Nair S Bhasker Tan Raymond R. Foo Dominic C. Y. 《Clean Technologies and Environmental Policy》2023,25(7):2413-2431
Clean Technologies and Environmental Policy - Canada has made a commitment in the Paris Agreement to reduce its total greenhouse gas emissions by 40–45% from 2005 levels by year 2030... 相似文献
658.
Dominic N. McBrayer Uttam Ghosh Muralikrishna Lella Crissey D. Cameron Yftah Tal-Gan 《Chembiochem : a European journal of chemical biology》2023,24(1):e202200527
As multidrug-resistant bacteria become a more pressing risk to human health, alternate approaches to treating bacterial infections are being increasingly investigated. Enterococcus faecalis is an opportunistic pathogen responsible for a large percentage of secondary enterococci infections. Its pathogenicity has been shown to be largely dependent on a cell-density communication mechanism, termed quorum sensing. In this study, we conducted a systematic investigation of the lactone-containing macrocyclic signaling peptide used by E. faecalis for Fsr-mediated communication, termed gelatinase biosynthesis activating pheromone (GBAP). Specifically, through a combination of the on-resin sub-monomer and solution phase peptoid building block synthesis approaches, we successfully synthesized a library of peptoid-peptide hybrid analogs of GBAP and determined the biological effects associated with the introduction of the peptoid (N-alkyl glycine derivative) modifications. Within the macrocycle region of the peptide, as have been seen with other modifications, the F7 site was unusually tolerant toward peptoid modification, compared with other macrocyclic sites. Interestingly, within the exocyclic tail, peptoid modification at the N2 site completely abolished activity, a first for a single tail modification. 相似文献
659.
Dr. Alexis J. A. Hennessy Wenli Huang Chloé Savary Prof. Dominic J. Campopiano 《Chembiochem : a European journal of chemical biology》2022,23(4):e202100411
The synthesis of amides through acid and amine coupling is one of the most commonly used reactions in medicinal chemistry, yet still requires atom-inefficient coupling reagents. There is a current demand to develop greener, biocatalytic approaches to amide bond formation. The nitrile synthetase (NS) enzymes are a small family of ATP-dependent enzymes which catalyse the transformation of a carboxylic acid into the corresponding nitrile via an amide intermediate. The Bacillus subtilis QueC (BsQueC) is an NS involved in the synthesis of 7-cyano-7-deazaguanine (CDG) natural products. Through sequence homology and structural analysis of BsQueC we identified three highly conserved residues, which could potentially play important roles in NS substrate binding and catalysis. Rational engineering led to the creation of a NS K163A/R204A biocatalyst that converts the CDG acid into the primary amide, but does not proceed to the nitrile. This study suggests that NSs could be further developed for coupling agent-free, amide-forming biocatalysts. 相似文献
660.
Dominic T. Meiers Maximilian Rothammer Maximilian Maier Cordt Zollfrank Georg von Freymann 《Advanced Engineering Materials》2023,25(11):2370037
The great flexibility of direct laser writing (DLW) arises from the possibility to fabricate precise three-dimensional structures on very small scales as well as the broad range of applicable materials. However, there is still a vast number of promising materials, which are currently inaccessible requiring the continuous development of novel photoresists. Herein, a new bio-sourced resist is reported that uses the monomeric unit of chitin, N-acetyl-D-glucosamine, paving the way from existing hydrogel resists based on animal carbohydrates to a new class of non-hydrogel ones. In addition, it is shown that the combined use of two photoinitiators is advantageous over the use of a single one. In this approach, the first photoinitiator is a good two-photon absorber at the applied wavelength, while the second photoinitiator exhibits poor two-photon absorbtion abilities, but is better suited for cross-linking of the monomer. The first photoinitiator absorbs the light acting as a sensitizer and transfers the energy to the second initiator, which subsequently forms a radical and initializes the polymerization. This sensitization effect enables a new route to utilize reactive photointiators with a small two-photon absorption cross section for DLW without changing their chemical structure. 相似文献