DFT Virtual Screening Identifies Rhodium–Amidinate Complexes As Potential Homogeneous Catalysts for Methane-to-Methanol Oxidation

In the search for new organometallic catalysts for low-temperature selective conversion of CH_4 to CH_3OH, we apply quantum mechanical virtual screening to select the optimum combination of ligand and solvent on rhodium to achieve low barriers for CH_4 activation and functionalization to recommend for experimental validation. Here, we considered Rh because its lower electronegativity compared with Pt and Pd may allow it to avoid poisoning by coordinating media. We report quantum mechanical predictions (including implicit and explicit solvation) of the mechanisms for Rh^(III)(NN) and Rh^(III)(NN^F) complexes [where (NN) = bis(N-phenyl)benzylamidinate and (NN^F) = bis(N-pentafluorophenyl)pentafluorobenzylamidinate] to catalytically activate and functionalize methane using trifluoroacetic acid (TFAH) or water as a solvent. In particular, we designed the (NN^F) ligand as a more electrophilic analogue to the (NN) ligand, and our results predict the lowest transition state barrier (ΔG‡ = 27.6 kcal/mol) for methane activation in TFAH from a pool of four different classes of ligands. To close the catalytic cycle, the functionalization of methylrhodium intermediates was also investigated, involving carbon–oxygen bond formation via S_N2 attack by solvent, or S_R2 attack by a vanadium oxo. Activation barriers for the functionalization of methylrhodium intermediates via nucleophilic attack are lower when the solvent is water, but CH_4 activation barriers are higher. In addition, we have found a correlation between CH_4 activation barriers and rhodium–methyl bond energies that allow us to predict the activation transition state energies for future ligands, as well

De rol van de overheid

Gesprek met als onderwerp: De rol van de overheid in de huidige verzorgingsstaa

Arene C–H activation using Rh(I) catalysts supported by bidentate nitrogen chelates

The Rh(I) complexes [(^(Fl)DAB)Rh(coe)(TFA)] (1) and [(BOZO)Rh(coe)(TFA)] (2) [^(Fl)DAB = N,N-bis-(pentafluorophenyl)-2,3-dimethyl-1,4-diaza-1,3-butadiene, coe = cyclooctene, TFA = trifluoroacetate, BOZO = bis(2-oxazolin-2-yl)] are efficient catalyst precursors for H/D exchange between arenes and DTFA. Catalyst precursor 1 exhibits a TOF of 0.06 s^(−1) at 150 °C for benzene H/D exchange. DFT calculations revealed that H/D exchange through reversible oxidative addition or internal electrophilic substitution of benzene is a viable pathway

Identification and microbial production of a terpene-based advanced biofuel

Rising petroleum costs, trade imbalances and environmental concerns have stimulated efforts to advance the microbial production of fuels from lignocellulosic biomass. Here we identify a novel biosynthetic alternative to D2 diesel fuel, bisabolane, and engineer microbial platforms for the production of its immediate precursor, bisabolene. First, we identify bisabolane as an alternative to D2 diesel by measuring the fuel properties of chemically hydrogenated commercial bisabolene. Then, via a combination of enzyme screening and metabolic engineering, we obtain a more than tenfold increase in bisabolene titers in Escherichia coli to >900 mg l−1. We produce bisabolene in Saccharomyces cerevisiae (>900 mg l−1), a widely used platform for the production of ethanol. Finally, we chemically hydrogenate biosynthetic bisabolene into bisabolane. This work presents a framework for the identification of novel terpene-based advanced biofuels and the rapid engineering of microbial farnesyl diphosphate-overproducing platforms for the production of biofuels

Guiding Ethical Principles in Engineering Biology Research

Engineering biology is being applied toward solving or mitigating some of the greatest challenges facing society. As with many other rapidly advancing technologies, the development of these powerful tools must be considered in the context of ethical uses for personal, societal, and/or environmental advancement. Researchers have a responsibility to consider the diverse outcomes that may result from the knowledge and innovation they contribute to the field. Together, we developed a Statement of Ethics in Engineering Biology Research to guide researchers as they incorporate the consideration of long-term ethical implications of their work into every phase of the research lifecycle. Herein, we present and contextualize this Statement of Ethics and its six guiding principles. Our goal is to facilitate ongoing reflection and collaboration among technical researchers, social scientists, policy makers, and other stakeholders to support best outcomes in engineering biology innovation and development

Functional expression and characterization of five wax ester synthases in Saccharomyces cerevisiae and their utility for biodiesel production

<p>Abstract</p> <p>Background</p> <p>Wax ester synthases (WSs) can synthesize wax esters from alcohols and fatty acyl coenzyme A thioesters. The knowledge of the preferred substrates for each WS allows the use of yeast cells for the production of wax esters that are high-value materials and can be used in a variety of industrial applications. The products of WSs include fatty acid ethyl esters, which can be directly used as biodiesel.</p> <p>Results</p> <p>Here, heterologous WSs derived from five different organisms were successfully expressed and evaluated for their substrate preference in <it>Saccharomyces cerevisiae</it>. We investigated the potential of the different WSs for biodiesel (that is, fatty acid ethyl esters) production in <it>S. cerevisiae</it>. All investigated WSs, from <it>Acinetobacter baylyi </it>ADP1, <it>Marinobacter hydrocarbonoclasticus </it>DSM 8798, <it>Rhodococcus opacus </it>PD630, <it>Mus musculus </it>C57BL/6 and <it>Psychrobacter arcticus </it>273-4, have different substrate specificities, but they can all lead to the formation of biodiesel. The best biodiesel producing strain was found to be the one expressing WS from <it>M. hydrocarbonoclasticus </it>DSM 8798 that resulted in a biodiesel titer of 6.3 mg/L. To further enhance biodiesel production, acetyl coenzyme A carboxylase was up-regulated, which resulted in a 30% increase in biodiesel production.</p> <p>Conclusions</p> <p>Five WSs from different species were functionally expressed and their substrate preference characterized in <it>S. cerevisiae</it>, thus constructing cell factories for the production of specific kinds of wax ester. WS from <it>M. hydrocarbonoclasticus </it>showed the highest preference for ethanol compared to the other WSs, and could permit the engineered <it>S. cerevisiae </it>to produce biodiesel.</p

CCSD(T) Study of CD3-O-CD3 and CH3-O-CD3 Far-Infrared Spectra

From a vibrationally corrected 3D potential energy surface determined with highly correlated ab initio calculations (CCSD(T)), the lowest vibrational energies of two dimethyl-ether isotopologues, 12CH3–16O–12CD3 (DME-d3) and 12CD3–16O–12CD3 (DME-d6), are computed variationally. The levels that can be populated at very low temperatures correspond to the COC-bending and the two methyl torsional modes. Molecular symmetry groups are used for the classification of levels and torsional splittings. DME-d6 belongs to the G36 group, as the most abundant isotopologue 12CH3–16O–12CH3 (DME-h6), while DME-d3 is a G18 species. Previous assignments of experimental Raman and far-infrared spectra are discussed from an effective Hamiltonian obtained after refining the ab initio parameters. Because a good agreement between calculated and experimental transition frequencies is reached, new assignments are proposed for various combination bands corresponding to the two deuterated isotopologues and for the 020 → 030 transition of DME-d6. Vibrationally corrected potential energy barriers, structural parameters, and anharmonic spectroscopic parameters are provided. For the 3N – 9 neglected vibrational modes, harmonic and anharmonic fundamental frequencies are obtained using second-order perturbation theory by means of CCSD and MP2 force fields. Fermi resonances between the COC-bending and the torsional modes modify DME-d3 intensities and the band positions of the torsional overtones

COSPAR Sample Safety Assessment Framework (SSAF).

The Committee on Space Research (COSPAR) Sample Safety Assessment Framework (SSAF) has been developed by a COSPAR appointed Working Group. The objective of the sample safety assessment would be to evaluate whether samples returned from Mars could be harmful for Earth's systems (e.g., environment, biosphere, geochemical cycles). During the Working Group's deliberations, it became clear that a comprehensive assessment to predict the effects of introducing life in new environments or ecologies is difficult and practically impossible, even for terrestrial life and certainly more so for unknown extraterrestrial life. To manage expectations, the scope of the SSAF was adjusted to evaluate only whether the presence of martian life can be excluded in samples returned from Mars. If the presence of martian life cannot be excluded, a Hold & Critical Review must be established to evaluate the risk management measures and decide on the next steps. The SSAF starts from a positive hypothesis (there is martian life in the samples), which is complementary to the null-hypothesis (there is no martian life in the samples) typically used for science. Testing the positive hypothesis includes four elements: (1) Bayesian statistics, (2) subsampling strategy, (3) test sequence, and (4) decision criteria. The test sequence capability covers self-replicating and non-self-replicating biology and biologically active molecules. Most of the investigations associated with the SSAF would need to be carried out within biological containment. The SSAF is described in sufficient detail to support planning activities for a Sample Receiving Facility (SRF) and for preparing science announcements, while at the same time acknowledging that further work is required before a detailed Sample Safety Assessment Protocol (SSAP) can be developed. The three major open issues to be addressed to optimize and implement the SSAF are (1) setting a value for the level of assurance to effectively exclude the presence of martian life in the samples, (2) carrying out an analogue test program, and (3) acquiring relevant contamination knowledge from all Mars Sample Return (MSR) flight and ground elements. Although the SSAF was developed specifically for assessing samples from Mars in the context of the currently planned NASA-ESA MSR Campaign, this framework and the basic safety approach are applicable to any other Mars sample return mission concept, with minor adjustments in the execution part related to the specific nature of the samples to be returned. The SSAF is also considered a sound basis for other COSPAR Planetary Protection Category V, restricted Earth return missions beyond Mars. It is anticipated that the SSAF will be subject to future review by the various MSR stakeholders