| 1. |
- Beal, Jacob, et al.
(author)
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Robust estimation of bacterial cell count from optical density
- 2020
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In: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
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Journal article (peer-reviewed)abstract
- Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data.
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| 2. |
- Dupe, Antoine, et al.
(author)
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Dioxomolybdenum(VI) and -tungsten(VI) Complexes with Multidentate Aminobisphenol Ligands as Catalysts for Olefin Epoxidation
- 2015
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In: European Journal of Inorganic Chemistry. - : Wiley. - 1099-0682 .- 1434-1948. ; :21, s. 3572-3579
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Journal article (peer-reviewed)abstract
- The synthesis of four molybdenum and tungsten complexes bearing tetradentate tripodal amino bisphenolate ligands with either hydroxyethylene (1a) or hydroxyglycolene (1b) substituents is reported. The molybdenum dioxo complexes [MoO2L] (L = 2a, 2b) and tungsten complexes [WO2L] (3a, 3b) were synthesized using [MoO2(acac)(2)] and [W(eg)(3)] (eg = 1,2-ethanediolato, ethylene glycolate), respectively, as precursors. All complexes were characterized by spectroscopic means as well as by single-crystal X-ray diffraction analyses. The latter reveal, in all cases, hexacoordinate complexes in which the hydrogen atom of the hydroxy group is involved in hydrogen bonding with one of the metal oxo groups. In the case of the glycol substituent, the ether oxygen atom is coordinated to the metal whereas the hydroxy group remains uncoordinated. The complexes were tested as catalysts in the epoxidation of cyclooctene under eco-friendly conditions, using an aqueous solution of H2O2 as the oxidant and dimethyl carbonate (DMC) as solvent or neat conditions, as substitutes for chlorinated solvents. Molybdenum complexes 2a and 2b showed good catalytic activity using H2O2 without added solvent, and tungsten complexes 3a and 3b showed very high activity in the epoxidation of cyclooctene using H2O2 and DMC as solvents.
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| 3. |
- Hossain, Kamal, et al.
(author)
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Dioxidomolybdenum(VI) and -tungsten(VI) complexes with tripodal amino bisphenolate ligands as epoxidation and oxo-transfer catalysts
- 2017
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In: Polyhedron. - : Elsevier BV. - 0277-5387. ; 134, s. 275-281
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Journal article (peer-reviewed)abstract
- The molybdenum(VI) and tungsten(VI) complexes [MO2(L)] (M = Mo (1), W (2), H2L = bis(2-hydroxy-3,5-di-tert-butybenzyl)morpholinylethylamine) were synthesized and the complexes were used to catalyze oxotransfer reactions, viz. sulfoxidation, epoxidation and benzoin oxidation. For comparison, the same reactions were catalyzed using the known complexes [MO2(L′)] (M = Mo (3), W (4), H2L′ = bis(2-hydroxy-3,5-di-tert-butybenzyl)ethanolamine) and [MO2(L″)] (M = Mo (5), W (6), H2L″ = bis(2-hydroxy-3,5-di-tert-butybenzyl)diethyleneglycolamine). The oxo atom transfer activity between DMSO and benzoin at 120 °C was identical for all studied catalysts. Reasonable catalytic activity was observed for sulfoxidation by the molybdenum complexes, but all tungsten complexes were found to be inactive. Similarly, the molybdenum complex 1 exhibited relatively good epoxidation activity, while the corresponding tungsten complex 2 catalyzed only the epoxidation of cis-cyclooctene with low activity.
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| 4. |
- Hossain, Kamal, et al.
(author)
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Oxygen atom transfer catalysis by dioxidomolybdenum(VI) complexes of pyridyl aminophenolate ligands
- 2021
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In: Polyhedron. - : Elsevier BV. - 0277-5387. ; 205
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Journal article (peer-reviewed)abstract
- A series of new cationic dioxidomolybdenum(VI) complexes [MoO2(Ln)]PF6 (2–5) with the tripodal tetradentate pyridyl aminophenolate ligands HL2-HL5 have been synthesized and characterized. Ligands HL2-HL4 carry substituents in the 4-position of the phenolate ring, viz. Cl, Br and NO2, respectively, whereas the ligand HL5, N-(2-hydroxy-3,5-di-tert-butylbenzyl)-N,N-bis(2-pyridylmethyl)amine, is a derivative of 3,5-di-tert-butylsalicylaldehyde. X-ray crystal structures of complexes 2, 3 and 5 reveal that they have a distorted octahedral geometry with the bonding parameters around the metal centres being practically similar. Stoichiometric oxygen atom transfer (OAT) properties of 5 with PPh3 were investigated using UV–Vis, 31P NMR and mass spectrometry. In CH2Cl2 solution, a dimeric Mo(V) complex [(µ-O){MoO(L5)}2](PF6)2 6 was formed while in methanol solution an air-sensitive Mo(IV) complex [MoO(OCH3)(L5)] 7 was obtained. The solid-state structure of the µ-oxo bridged dimer 6 was determined by X-ray diffraction. Complex 7 is unstable under ambient conditions and capable of reducing DMSO, thus showing reactivity analogous to that of DMSO reductases. Similarly, the OAT reactions of complexes 2–4 also resulted in the formation of dimeric Mo(V) and unsaturated monomeric Mo(IV) complexes that are analogous to complexes 6 and 7. Catalytic OAT at 25 °C could also be observed, using complexes 1–5 as catalysts for oxidation of PPh3 in deuterated dimethylsulfoxide (DMSO‑d6), which functioned both as a solvent and oxidant. All complexes were also tested as catalysts for sulfoxidation of methyl-p-tolylsulfide and epoxidation of various alkene substrates with tert-butyl hydroperoxide (TBHP) as an oxidant. Complex 1 did not exhibit any sulfoxidation activity under the conditions used, while 2–5 catalyzed the sulfoxidation of methyl-p-tolylsulfide. Only complexes 2 and 3, with ligands containing halide substituents, exhibited good to moderate activity for epoxidation of all alkene substrates studied, and, in general, good activity for all molybdenum(VI) catalysts was only exhibited when cis-cyclooctene was used as a substrate. No complex catalysed epoxidation of cis-cyclooctene when an aqueous solution of H2O2 was used as potential oxidant.
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| 5. |
- Hossain, Md Kamal, et al.
(author)
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An experimental and theoretical study of a heptacoordinated tungsten(VI) complex of a noninnocent phenylenediamine bis(phenolate) ligand
- 2018
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In: Inorganic Chemistry Communications. - : Elsevier BV. - 1387-7003. ; 93, s. 149-152
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Journal article (peer-reviewed)abstract
- [W(N2O2)(HN2O2)] (H4N2O2 = N,N′-bis(3,5-di-tert-butyl-2-hydroxyphenyl)-1,2-phenylenediamine) with a noninnocent ligand was formed by reaction of the alkoxide precursor [W(eg)3] (eg = the 1,2-ethanediolate dianion) with two equivalents of ligand. The phenol groups on one of the ligands are completely deprotonated and the ligand coordinates in a tetradentate fashion, whereas the other ligand is tridentate with one phenol having an intact OH group. The molecular structure, magnetic measurements, EPR spectroscopy, and density functional theory calculations indicate that the complex is a stable radical with the odd electron situated on the tridentate amidophenoxide ligand. The formal oxidation state of the metal center is W(VI), with the paramagnetic properties being due to the unpaired electron on the ligand.
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| 6. |
- Hossain, Md Kamal, et al.
(author)
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Catalytic epoxidation using dioxidomolybdenum(VI) complexes with tridentate aminoalcohol phenol ligands
- 2019
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In: Inorganica Chimica Acta. - : Elsevier BV. - 0020-1693. ; 486, s. 17-25
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Journal article (peer-reviewed)abstract
- Reaction of the tridentate aminoalcohol phenol ligands 2,4-di-tert-butyl-6-(((2 hydroxyethyl)(methyl)amino)methyl)phenol (H2L1) and 2,4-di-tert-butyl-6-(((1-hydroxybutan-2-yl)amino)methyl)phenol (H2L2) with [MoO2(acac)2] in methanol solutions resulted in the formation of [MoO2(L1)(MeOH)] (1) and [MoO2(L2)(MeOH)] (3), respectively. In contrast, the analogous reactions in acetonitrile afforded the dinuclear complexes [Mo2O2(μ-O)2(L1)2] (2) and [Mo2O2(μ-O)2(L2)2] (4). The corresponding reactions with the potentially tetradentate ligand 3-((3,5-di-tert-butyl-2-hydroxybenzyl)(methyl)amino)propane-1,2-diol (H3L3) led to the formation of the mononuclear complex [MoO2(L3)(MeOH)] (5) in methanol while in acetonitrile solution a trinuclear structure [Mo3O3(μ-O)3(L3)3] (6) was obtained. In both cases, the ligand moiety L3 coordinated in a tridentate fashion. The catalytic activities of complexes 1–6 in epoxidation of five different olefins, S1-5, with tert-butyl hydroperoxide and hydrogen peroxide were studied. The catalytic activities were found to be moderate to good for the reaction of substrate cis-cyclooctene S1, while all complexes were less active in the epoxidation of the more challenging substrates S2-5. The molecular structures of 1, 2, 4 and 6 were determined by single crystal X-ray diffraction analyses.
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| 7. |
- Hossain, Md Kamal, et al.
(author)
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Cis- and trans molybdenum oxo complexes of a prochiral tetradentate aminophenolate ligand : Synthesis, characterization and oxotransfer activity
- 2020
-
In: Polyhedron. - : Elsevier BV. - 0277-5387. ; 178
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Journal article (peer-reviewed)abstract
- Reaction of [MoO2Cl2(dmso)2] with the tetradentate O2N2 donor ligand papy [H2papy = N-(2-hydroxybenzyl)-N-(2-picolyl)glycine] leads to formation of the dioxomolybdenum(VI) complex [MoO2(papy)] (1) as a mixture of cis and trans isomers. Recrystallization from methanol furnishes solid cis-1, whereas the use of a dichloromethane-hexane mixture allows for the isolation of the trans-1 isomer. Both isomers have been structurally characterized by X-ray crystallography and the energy difference between the isomeric pair has been investigated by electronic structure calculations. Optimization of two configurational isomers in the gas phase predicts the trans isomer to lie 2.5 kcal/mol lower in energy (ΔG) than the cis isomer, which is inconsistent with the solution NMR data in d3-MeCN that exhibit a Keq of ca. 3 at 298 K for the trans ⇌ cis equilibrium. The DFT-computed energy difference is significantly improved (Keq = 5.4) by the inclusion of the MeCN solvent using the polarization continuum model (PCM). Density functional calculations reveal that the isomerization proceeds via a Ray-Dutt twist mechanism with a barrier of 14.5 kcal/mol, which is in accordance with the 1H NMR spectral data and the rapid equilibration of these isomers in solution. The catalytic reactivity of [MoO2(papy)] in the epoxidation of cis-cyclooctene is described, as well as its ability to effect oxo transfer from DMSO to PPh3.
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| 8. |
- Hossain, Md Kamal, et al.
(author)
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Oxovanadium(V) complexes with tripodal bisphenolate and monophenolate ligands : Syntheses, structures and catalytic activities
- 2019
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In: Inorganica Chimica Acta. - : Elsevier BV. - 0020-1693. ; 487, s. 112-119
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Journal article (peer-reviewed)abstract
- The reactions between [VO(acac)2] (acac– = acetylacetonate) and the tripodal amino bisphenols 6,6′-(((2-morpholinoethyl)azanediyl)bis(methylene))bis(2,4-di-tert-butylphenol) (H2L1) and 6,6′-(((thiophen-2-ylmethyl)azanediyl)bis(methylene))bis(2,4-di-tert-butylphenol) (H2L2) as well as the tetradentate amino phenol 2,2′-((3,5-di-tert-butyl-2-hydroxybenzyl)azanediyl)bis(ethan-1-ol) (H3L3) afford the complexes [VO(L1)(OMe)] (1), [VO(L2)(acac)] (2) and [VO(L3)] (3), correspondingly. Complexes 1 and 3 can also be prepared using VOSO4·xH2O or [VO(OPr)3] as vanadium precursors. When [VO(acac)2] or VOSO4·xH2O is used, mononuclear oxovanadium(V) complexes are formed upon oxidation of the metal precursor. Single crystal X-ray structure analysis show that complexes 1 and 2 have distorted octahedral coordination spheres, in which the amino bisphenolate coordinates in a tetradentate or tridentate manner, respectively, and the coordination spheres are completed by methoxy or acetylacetonato ligands. Complex 3 has a slightly distorted trigonal bipyramidal geometry with an NO4 coordination environment. All three complexes can catalyze epoxidation of cis-cyclooctene at 50 °C with tert-butyl hydroperoxide (TBHP) or H2O2 as an oxygen source, and sulfoxidation of thioanisole or methyl-p-tolylsulfide proceeds at 25 °C using the same oxidants.
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| 9. |
- Jauhiainen, Jyrki, et al.
(author)
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Reviews and syntheses: Greenhouse gas exchange data from drained organic forest soils-A review of current approaches and recommendations for future research
- 2019
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In: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 16:23, s. 4687-4703
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Journal article (peer-reviewed)abstract
- © Author(s) 2019. Drained organic forest soils in boreal and temperate climate zones are believed to be significant sources of the greenhouse gases (GHGs) carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O), but the annual fluxes are still highly uncertain. Drained organic soils exemplify systems where many studies are still carried out with relatively small resources, several methodologies and manually operated systems, which further involve different options for the detailed design of the measurement and data analysis protocols for deriving the annual flux. It would be beneficial to set certain guidelines for how to measure and report the data, so that data from individual studies could also be used in synthesis work based on data collation and modelling. Such synthesis work is necessary for deciphering general patterns and trends related to, e.g., site types, climate, and management, and the development of corresponding emission factors, i.e. estimates of the net annual soil GHG emission and removal, which can be used in GHG inventories. Development of specific emission factors also sets prerequisites for the background or environmental data to be reported in individual studies. We argue that wide applicability greatly increases the value of individual studies. An overall objective of this paper is to support future monitoring campaigns in obtaining high-value data.We analysed peer-reviewed public cations presenting CO2, CH4 and N2O flux data for drained organic forest soils in boreal and temperate climate zones, focusing on data that have been used, or have the potential to be used, for estimating net annual soil GHG emissions and removals. We evaluated the methods used in data collection and identified major gaps in background or environmental data. Based on these, we formulated recommendations for future research.
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