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Molecules (Basel, Switzerland) Jul 2017Because of their great structural diversity and multitude of chemical properties, N-heterocyclic carbenes (NHCs) have been utilized in a variety of capacities. Most... (Review)
Review
Because of their great structural diversity and multitude of chemical properties, N-heterocyclic carbenes (NHCs) have been utilized in a variety of capacities. Most recently, NHCs have been utilized as carrier molecules for many transition metals in medicinal chemistry. Specifically, Ag(I)-NHCs have been investigated as potent antibacterial agents and chemotherapeutics and have shown great efficacy in both in vitro and in vivo studies. Ag(I)-NHC compounds have been shown to be effective against a wide range of both Gram-positive and Gram-negative bacterial strains. Many compounds have also shown great efficacy as antitumor agents demonstrating comparable or better antitumor activity than standard chemotherapeutics such as cisplatin and 5-fluorouracil. While these compounds have shown great promise, clinical use has remained an unattained goal. Current research has been focused upon synthesis of novel Ag(I)-NHC compounds and further investigations of their antibacterial and antitumor activity. This review will focus on recent advances of Ag(I)-NHCs in medicinal applications.
Topics: Anti-Bacterial Agents; Heterocyclic Compounds; Imidazoles; Methane; Salts; Silver
PubMed: 28749425
DOI: 10.3390/molecules22081263 -
Current Opinion in Biotechnology Oct 2017The surge in reports of heme-dependent proteins as catalysts for abiotic, synthetically valuable carbene and nitrene transfer reactions dramatically illustrates the... (Review)
Review
The surge in reports of heme-dependent proteins as catalysts for abiotic, synthetically valuable carbene and nitrene transfer reactions dramatically illustrates the evolvability of the protein world and our nascent ability to exploit that for new enzyme chemistry. We highlight the latest additions to the hemoprotein-catalyzed reaction repertoire (including carbene Si-H and C-H insertions, Doyle-Kirmse reactions, aldehyde olefinations, azide-to-aldehyde conversions, and intermolecular nitrene C-H insertion) and show how different hemoprotein scaffolds offer varied reactivity and selectivity. Preparative-scale syntheses of pharmaceutically relevant compounds accomplished with these new catalysts are beginning to demonstrate their biotechnological relevance. Insights into the determinants of enzyme lifetime and product yield are providing generalizable cues for engineering heme-dependent proteins to further broaden the scope and utility of these non-natural activities.
Topics: Biocatalysis; Cyclopropanes; Hemeproteins; Imines; Methane; Protein Engineering
PubMed: 28711855
DOI: 10.1016/j.copbio.2017.06.005 -
Chemical & Pharmaceutical Bulletin 2012Effective methods of ligand design have been highly sought due to the significant roles of ligands in controlling metal catalyses. In particular, easy-to-handle ligands... (Review)
Review
Effective methods of ligand design have been highly sought due to the significant roles of ligands in controlling metal catalyses. In particular, easy-to-handle ligands to realize high reaction efficacy, substrate tolerance, and environmental friendliness are desirable. Novel bidentate ligands containing N-heterocyclic carbene and thioether moieties were developed based on findings of hemilabile coordination, whose precursors were crystalline solids stable enough to handle and store in the air. The thioether-imidazolinium carbene ligand successfully brought out high catalyst performance of palladium in the catalytic arylation of aldehydes with organoboron reagents, which tolerated a diverse range of substrates including poorly reactive, sterically hindered, and heterocyclic compounds. This process was applied to gram-scale synthesis using only water as solvent with high efficiency and also achieved the effective one-pot synthesis of 3-arylphthalides known as useful biologically active agents and important synthetic intermediates for naturally occurring compounds.
Topics: Aldehydes; Boron Compounds; Catalysis; Heterocyclic Compounds; Imidazoles; Ligands; Methane; Palladium; Sulfides
PubMed: 22466724
DOI: 10.1248/cpb.60.419 -
Chemistry, An Asian Journal Apr 2022Isolation of cyclic (alkyl) amino carbenes (cAACs) in 2005 has been a major achievement in the field of stable carbenes due to their better electronic properties. cAACs... (Review)
Review
Isolation of cyclic (alkyl) amino carbenes (cAACs) in 2005 has been a major achievement in the field of stable carbenes due to their better electronic properties. cAACs and bicyclic(alkyl)(amino)carbene (BicAAC) in essence are the most electrophilic as well as nucleophilic carbenes are known till date. Due to their excellent electronic properties in terms of nucleophilic and electrophilic character, cAACs have been utilized in different areas of chemistry, including stabilization of low valent main group and transition metal species, activation of small molecules, and catalysis. The applications of cAACs in catalysis have opened up new avenues of research in the field of cAAC chemistry. This review summarizes the major results of cAAC chemistry published until August 2021.
Topics: Catalysis; Methane
PubMed: 34989475
DOI: 10.1002/asia.202101301 -
Molecules (Basel, Switzerland) Aug 2022This study presents a biophotocatalytic system as a sustainable technology for the recovery of clean water and renewable energy from wastewater, thereby providing a...
This study presents a biophotocatalytic system as a sustainable technology for the recovery of clean water and renewable energy from wastewater, thereby providing a unique opportunity to drive industrialization and global sustainable development throughputs. Herein, inhouse magnetized photocatalyst (Fe-TiO) with surface area 62.73 m/g synthesized via co-precipitation, was hypothesized to hasten an up-flow anaerobic sludge blanket (UASB) reactor for the treatment of local South Africa municipality wastewater with the benefit of high-quality biogas production. A lab scale UASB process with a working volume of 5 L coupled with two UV-lights (T8 blacklight-blue tube, 365 nm, 18 W) was operated batchwise under mesophilic conditions for the period of 30 days with a constant organic load charge of 2.76 kg COD/m. d. This biophotocatalytic system performance was investigated and compared with and without the Fe-TiO charge (2-6 g) with respect to effluent quality, biogas production and CO methanation. Using chemical oxygen demand (COD) measured as the degree of degradation of the pollutants, the best efficiency of 93% COD removal was achieved by a 4 g Fe-TiO charge at 14 days and pH of 7.13, as compared to zero charge where only 49.6% degradation was achieved. Under the same charge, cumulative biogas and methane content of 1500 mL/g COD.d and 85% were respectively attained as compared with the control with 400 mL/g COD.d and 65% methane content. Also, the energy produced can be used to offset the energy utilized by the UV-light for the wastewater abatement and other limitations of photocatalysis. The BP system was found to be an eco-friendly and cost-effective technology to be explored in water treatment settings.
Topics: Anaerobiosis; Biofuels; Bioreactors; Carbon Dioxide; Methane; Sewage; Titanium; Waste Disposal, Fluid; Wastewater
PubMed: 36014454
DOI: 10.3390/molecules27165213 -
Microbial Biotechnology Sep 2009The position of high-rate anaerobic technology (HR-AnWT) in the wastewater treatment and bioenergy market can be enhanced if the range of suitable substrates is... (Review)
Review
The position of high-rate anaerobic technology (HR-AnWT) in the wastewater treatment and bioenergy market can be enhanced if the range of suitable substrates is expanded. Analyzing existing technologies, applications and problems, it is clear that, until now, wastewaters with high lipids content are not effectively treated by HR-AnWT. Nevertheless, waste lipids are ideal potential substrates for biogas production, since theoretically more methane can be produced, when compared with proteins or carbohydrates. In this minireview, the classical problems of lipids methanization in anaerobic processes are discussed and new concepts to enhance lipids degradation are presented. Reactors operation, feeding strategies and prospects of technological developments for wastewater treatment are discussed. Long-chain fatty acids (LCFA) degradation is accomplished by syntrophic communities of anaerobic bacteria and methanogenic archaea. For optimal performance these syntrophic communities need to be clustered in compact aggregates, which is often difficult to achieve with wastewaters that contain fats and lipids. Driving the methane production from lipids/LCFA at industrial scale without risk of overloading and inhibition is still a challenge that has the potential for filling a gap in the existing processes and technologies for biological methane production associated to waste and wastewater treatment.
Topics: Anaerobiosis; Archaea; Bacteria; Biofuels; Energy Metabolism; Fatty Acids; Methane; Water Purification
PubMed: 21255287
DOI: 10.1111/j.1751-7915.2009.00100.x -
Metal Ions in Life Sciences 2014Methane, the major component of natural gas, has been in use in human civilization since ancient times as a source of fuel and light. Methanogens are responsible for... (Review)
Review
Biochemistry of methyl-coenzyme M reductase: the nickel metalloenzyme that catalyzes the final step in synthesis and the first step in anaerobic oxidation of the greenhouse gas methane.
Methane, the major component of natural gas, has been in use in human civilization since ancient times as a source of fuel and light. Methanogens are responsible for synthesis of most of the methane found on Earth. The enzyme responsible for catalyzing the chemical step of methanogenesis is methyl-coenzyme M reductase (MCR), a nickel enzyme that contains a tetrapyrrole cofactor called coenzyme F430, which can traverse the Ni(I), (II), and (III) oxidation states. MCR and methanogens are also involved in anaerobic methane oxidation. This review describes structural, kinetic, and computational studies aimed at elucidating the mechanism of MCR. Such studies are expected to impact the many ramifications of methane in our society and environment, including energy production and greenhouse gas warming.
Topics: Anaerobiosis; Animals; Catalysis; Energy-Generating Resources; Environment; Greenhouse Effect; Humans; Metalloproteins; Methane; Models, Molecular; Nickel; Oxidation-Reduction; Oxidoreductases; Protein Structure, Tertiary
PubMed: 25416393
DOI: 10.1007/978-94-017-9269-1_6 -
ChemistryOpen Jan 2023The indole moiety is an important N-heterocycle found in natural products, and a key structural component of many value-added chemicals including pharmaceuticals. In...
The indole moiety is an important N-heterocycle found in natural products, and a key structural component of many value-added chemicals including pharmaceuticals. In particular, bis(3-indolyl)methanes (BIMs) are an important subgroup of indoles, composed of two indole units. Herein, we report the development of a simple method to access BIMs derivatives in yields of up to 77 % by exploiting a tBuOK-mediated coupling reaction of indoles and benzyl alcohols.
Topics: Methane; Butanols; Indoles
PubMed: 36650736
DOI: 10.1002/open.202200265 -
Bioresource Technology Aug 2021Syngas from gasification of waste biomass is a mixture of carbon monoxide (CO), carbon dioxide (CO), and hydrogen (H), which can be utilized for the synthesis of...
Syngas from gasification of waste biomass is a mixture of carbon monoxide (CO), carbon dioxide (CO), and hydrogen (H), which can be utilized for the synthesis of biofuels such as methane (CH). The aim of the study research work was to demonstrate how syngas could be methanated and upgraded to natural gas quality (biomethane) in a fed-batch trickle-bed reactor system using either manure - (AD-M) or sludge-based (AD-WW) inoculum as microbial basis. The methanated syngas had a high concentration of CO and did not fulfil the criteria for natural gas quality biomethane. Further upgrading of syngas to biomethane could be achieved simultaneously in the same reactors by addition of exogenous H resulting in CH concentrations up to 91.0 ± 3.5% (AD-WW) and 95.3 ± 1.0% (AD-M). Microbial analysis indicated that the communities differed between AD-M and AD-WW demonstrating functional redundancy among the microbial communities of different inocula.
Topics: Biofuels; Bioreactors; Carbon Dioxide; Hydrogen; Methane; Sewage
PubMed: 33895671
DOI: 10.1016/j.biortech.2021.125183 -
Proceedings of the National Academy of... Sep 2020Lakes are considered the second largest natural source of atmospheric methane (CH). However, current estimates are still uncertain and do not account for diel...
Lakes are considered the second largest natural source of atmospheric methane (CH). However, current estimates are still uncertain and do not account for diel variability of CH emissions. In this study, we performed high-resolution measurements of CH flux from several lakes, using an automated and sensor-based flux measurement approach (in total 4,580 measurements), and demonstrated a clear and consistent diel lake CH flux pattern during stratification and mixing periods. The maximum of CH flux were always noted between 10:00 and 16:00, whereas lower CH fluxes typically occurred during the nighttime (00:00-04:00). Regardless of the lake, CH emissions were on an average 2.4 higher during the day compared to the nighttime. Fluxes were higher during daytime on nearly 80% of the days. Accordingly, estimates and extrapolations based on daytime measurements only most likely result in overestimated fluxes, and consideration of diel variability is critical to properly assess the total lake CH flux, representing a key component of the global CH budget. Hence, based on a combination of our data and additional literature information considering diel variability across latitudes, we discuss ways to derive a diel variability correction factor for previous measurements made during daytime only.
Topics: Circadian Rhythm; Environmental Monitoring; Lakes; Methane; Seasons
PubMed: 32817550
DOI: 10.1073/pnas.2006024117