Sodium hydroxide solutions are used in petroleum refining to remove hydrogen sulfide (H2S) and mercaptans from various hydrocarbon streams. The resulting sulfide-laden waste stream is called spent-sulfidic caustic. An aerobic enrichment culture was previously developed using a gas mixture of H2S and methylmercaptan (MeSH) as the soleenergy source. This culture has now been immobilized in a novel support matrix, DuP ont BIO-SEPTM beads, and is used to biotreat a refinery spent-sulfidic caustic containing both inorganic sulfide and mercaptans in a continuous flow, fluidized-bed column bioreactor. Complete oxidation of both inorganic and organic sulfur to sulfate was observed with no breakthrough of H2S and <2 ppmv of MeSH produced in the bioreactor outlet gas. Excessive buildup of sulfate (>12 g/L) in the bioreactor medium resulted in an upset condition evidenced by excessive MeSH breakthrough. Therefore, bioreactor performance was limited by the steady-state sulfate concentration. Further improvement in volumetric productivity of a bioreactor system based on this enrichment culture will be dependent on maintenance of sulfate concentrations below inhibitory levels.
In this study, a row of four analogous dopamine acryl- and methacrylamide derivatives, namely N-(3,4-dihydroxyphenyethyl) acrylamide, N-(3,4-dihydroxyphenyethyl) meth acrylamide, N-phenethyl methacrylamide, N-(4-hydroxyphenethyl) methacrylamide were synthesized and characterized by 1H-NMR and 13C-NMR, followed by further solvent-based radical polymerization with N-hydroxyethyl acrylamide. All copolymers were characterized by 1H-NMR, dynamic differential calorimetry, and gel permeation chromatography. The dependency of the used comonomer ratios to the molecular mass of the corresponding copolymers has been described. The synthesis of the various polymers serves as a feasibility study and provides important data for a future biometric application in the medical field. We synthesized N-(3,4-dihydroxyphenyethyl) acrylamide copolymer up to 80 mol% by free radical polymerization without using any protecting groups. All polymers show identical perfect adhesive properties by a simple scratch test. Further, the monomers were used as a photo reactive glue formulation to test its adherence to a medical titanium surface sample by tensile shear test. 相似文献
Correction for ‘Expanding medicinal chemistry into 3D space: metallofragments as 3D scaffolds for fragment-based drug discovery’ by Christine N. Morrison et al., Chem. Sci., 2020, 11, 1216–1225, https://doi.org/10.1039/C9SC05586J.The authors regret that in the original article, inhibitory values reported for some metallofragments were incorrect. Unfortunately, DMSO stock solutions of reportedly active ferrocene-based metallofragments were found to decompose in the presence of light, which resulted in inaccurate inhibition values. The authors maintain that the core conclusions of the paper are accurate and the utility of three-dimensional metal complexes for fragment-based drug discovery has merit.In the original article, ‘class A’ metallofragments are comprised of ferrocene derivatives (Fig. 1). Some of these ferrocene fragments (specifically those containing carbonyl groups) are reported as broadly inhibiting several protein targets. It was noted in our original report that the ferrocene scaffold was likely promiscuous due to its lipophilicity and potential redox activity, but that it might still serve as a useful metallofragment for fragment-based drug discovery (FBDD) campaigns. However, re-evaluation of these compounds against the influenza endonuclease (PAN) failed to reproduce our original inhibition results for the class A metallofragments using freshly prepared stocks, indicating a problem with the materials used in the original study.Open in a separate windowFig. 1Chemical structures of class A metallofragments.Several compounds from class A were originally reported as having near complete (100%) inhibition against PAN endonuclease at an inhibitor concentration of 200 μM (and2).2). However, when re-evaluated under identical conditions, using freshly prepared DMSO stock solutions, inhibition was only observed with one fragment of this class (A22, Fig. 1), with the previously reported highly active fragments (A4, A7–A21,
Open in a separate windowReported and re-evaluated percent inhibition values of representative metallofragments against PAN endonuclease at 200 μM inhibitor concentration. Each compound was tested in triplicate from either two or three independent experimentsa
Open in a separate windowIn the original article, one representative member of each metallofragment class was assessed for stability by NMR. Compound A1 (ferrocene) proved stable in DMSO and class A metallofragments were stored as DMSO stocks at −80 °C, but were not consistently protected from light. As noted above, many of the derivatives in class A contain a ferrocenyl carbonyl motif. It has been previously reported that ferrocenyl ketones can undergo photoaquation (λ > 280 nm) in wet DMSO to produce a monocyclopentadienyliron cation, the anionic ligand, and free cyclopentadiene.1 Suspecting issues with photostability, we dissolved several of the ferrocenyl fragments in DMSO-d6, exposed them to ambient room light (fluorescent light bulb), and monitored stability by NMR. Indeed, photoinstability was confirmed by the observance of free cyclopentadienyl peaks appearing in the 1H NMR spectrum (Fig. 2). It should also be noted that while the fresh stock of A22 retained significant inhibition against PAN, it also exhibits sensitivity to light in DMSO.Open in a separate windowFig. 2Compound A7 in DMSO-d6 (left) and after exposure to ambient light for 24 h (right) demonstrating the photoinstability of this compound.Based on these findings, the authors regret that the inhibitory data associated with class A metallofragments are incorrect, likely because of photodecomposition of these ferrocene derivatives. To confirm if other classes of metallofragments were correctly reported, a representative member of each class was evaluated against PAN endonuclease at an inhibitor concentration of 200 μM using freshly prepared DMSO stocks. Each compound was tested in triplicate in two or three independent experiments, with the addition of 2,4-dioxo-4-phenylbutanoic acid (DPBA) as a positive control.2 Fortunately, these experiments largely reproduced our original findings. Although several fragments showed slightly greater activity upon re-evaluation (J1, L1, M1, Fig. 3), only one fragment initially identified as a hit (>50% inhibition) failed to show activity when re-examined (F1, Fig. 3). Other than compound F1, all selected compounds designated as ‘hits’ (>50% inhibition) retained a high level of inhibitory activity upon re-evaluation. Taken together, the authors believe the inaccuracies stemming from photostability issues are limited to class A compounds; however, these inaccuracies would include all other inhibition data reported for class A compounds, including assay data against other enzyme targets, IC50 values, and thermal shift assay (TSA) binding data. Furthermore, the hit rate against each target is likely lower than reported, with PAN having an adjusted hit rate of ∼28% (20/71).Open in a separate windowFig. 3Chemical structures of representative metallofragments from each class re-examined for inhibition activity against PAN endonuclease.The authors maintain that three-dimensional metallofragments represent a useful new line of inquiry for FBDD and our ongoing studies seek to further test this hypothesis. The core message of our original study – the ability of metallofragments to be useful scaffolds for FBDD that occupy hard-to-access three-dimensional chemical space – remains unchanged. However, as demonstrated by our error, the authors acknowledge that metallofragments may pose unique challenges that must be carefully considered and controlled for when using them in FBDD campaigns.The authors would like to take this opportunity to thank the readers who alerted them to the concerns regarding the inhibitory activities and allowed them to reinvestigate. Both the authors and the Royal Society of Chemistry appreciate their support.The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers.相似文献
Precisely determining the intracellular concentrations of metabolites and signaling molecules is critical in studying cell biology. Fluorogenic RNA‐based sensors have emerged to detect various targets in living cells. However, it is still challenging to apply these genetically encoded sensors to quantify the cellular concentrations and distributions of targets. Herein, using a pair of orthogonal fluorogenic RNA aptamers, DNB and Broccoli, we engineered a modular sensor system to apply the DNB‐to‐Broccoli fluorescence ratio to quantify the cell‐to‐cell variations of target concentrations. These ratiometric sensors can be broadly applied for live‐cell imaging and quantification of metabolites, signaling molecules, and other synthetic compounds. 相似文献
Structural Chemistry - The newly measured ionization potential of atomic astatine is discussed and compared with that of the recently determined value for polonium and for the other atomic... 相似文献
The design of metal–organic frameworks (MOFs) that incorporate more than one metal cluster constituent is a challenging task. Conventional one-pot reaction protocols require judicious selection of ligand and metal ion precursors, yet remain unpredictable. Stable, preformed nanoclusters, with ligand shells that can undergo additional coordination-driven reactions, provide a platform for assembling multi-cluster solids with precision. Herein, a discrete Co6S8(PTA)6 (PTA=1,3,5-triaza-7-phosphaadamantane) superatomic-metalloligand is assembled into a three-dimensional (3D) coordination polymer comprising Cu4I4 secondary building units (SBUs). The resulting heterobimetallic framework ( 1 ) contains two distinct cluster constituents and bifunctional PTA linkers. Solid-state diffuse reflectance studies reveal that 1 is an optical semiconductor with a band-gap of 1.59 eV. Framework-modified electrodes exhibit reversible redox behavior in the solid state arising from the Co6S8 superatoms, which remain intact during framework synthesis. 相似文献
A new model for the location and distribution of carbonate ions in carbonated apatite was used to assign the IR spectra of A- and AB-carbonated apatites. The percentage of total carbonate as measured by the mass loss in the TGA of these compounds is in good agreement with the percentage obtained by combustion analysis. The decomposition of pure A-type carbonate appears at temperatures of 985–1123 °C, whereas the decomposition of AB-type carbonated apatites occurs in the range of 600–800 °C. This difference is attributed to changes in the environment of channel carbonate brought about by B-type substitution of carbonate for phosphate. In the presence of sodium ions, the channel is changed by substitution of sodium for calcium in order to accommodate the difference between the charge of the carbonate and phosphate ions. A thermodynamic cycle is introduced to rationalize the differences in decomposition temperatures of A- and B-type carbonate. Preferential loss of B-type carbonate upon heating to 600 °C also suggests the migration of B-type carbonate to A-sites.
Thymine-containing photoproducts with chromatographic properties similar to those of cyclobutyl pyrimidine dimers can be formed in [3H]-thymine-labeled DNA in solution by 313 nm ultraviolet radiation in the presence of para-aminobenzoic acid (PABA), a compound used in sunscreen preparations. In the absence of PABA, similar fluences of 313 nm radiation do not produce significant numbers of these photoproducts. The thymine-containing photoproducts can be reversed by 254 nm radiation so that the tritium label migrates with the mobility of thymine monomer, a behavior characteristic of thymine-containing cyclobutyl pyrimidine dimers. This result supports previous, but less direct, data from other laboratories indicating that PABA can sensitize dimer formation in the DNA of bacterial and mammalian cells. 相似文献
In the last several years, the modeling of emergency vehicle location has focussed on the temporal availability of the vehicles. Vehicles are not available for service when they are engaged in earlier calls. To incorporate this dynamic aspect into facility location decisions, models have been developed which provide additional levels of coverage. In this paper, two new models are derived from the probabilistic location set covering problem. These models allow the examination of the relationships between the number of facilities being located, the reliability that a vehicle will be available, and a coverage standard. In addition, these models incorporate sectoral specific estimates of the availability of the vehicles. Solution of these models reveals that the use of sectoral estimates leads to facility locations which are distributed to a greater spatial extent over the region to be serviced. 相似文献
The synthesis of N-alkoxycarbonyl and N-carboxamide derivatives of anti-inflammatory oxindoles is described. These compounds, sought as potential prodrugs of the parent anti-inflammatory agents, were obtained by ring opening of the oxadiazine dione intermediates formed by the treatment of 1-unsubstituted 3-acyloxindoles with chlorocarbonyl isocyanate. 相似文献