We present the first spectroscopic identification of hitherto unknown 1,1‐ethenediol, the enol tautomer of acetic acid. The title compound was generated in the gas phase through flash vacuum ...pyrolysis of malonic acid at 400 °C. The pyrolysis products were subsequently trapped in argon matrices at 10 K and characterized spectroscopically by means of IR and UV/Vis spectroscopy together with matching its spectral data with computations at the CCSD(T)/cc‐pCVTZ and B3LYP/6–311++G(2d,2p) levels of theory. Upon photolysis at λ=254 nm, the enol rearranges to acetic acid and ketene.
Finally made: The hitherto unreported 1,1‐ethenediol, the higher energy tautomer of acetic acid, was synthesized and spectroscopically characterized. It can be readily prepared through thermal decarboxylation of malonic acid, as has generally often been implied in the synthetically highly valuable reactions of 1,3‐dicarboxylic acids.
•Robust non-target bioanalytical screening for bioactive compounds was developed.•Eight-dimensional hyphenation: NP-HPTLC–UV/Vis/FLD–EDA–RP-HPLC–PDA–MS•Analyte trapping and online desalting reduced ...the transfer of bioassay salts to MS.•Orthogonal separations improved the separation power for complex samples.•Proof-of-principle was successfully made for active compounds in 18 cinnamon samples.
It is still a challenge to discover and identify individual bioactive compounds directly in multicomponent mixtures. Current workflows are too tedious for routine use. Hence, the hyphenation of separation and detection techniques is a powerful tool to maximize the information obtained by a single sample run. A robust eight-dimensional (8D) hyphenation was developed. Orthogonal separations, biological assay detection, analyte trapping, desalting, and physico-chemical detections were arranged in the following order, i.e. 1) normal phase high-performance thin-layer chromatography (NP-HPTLC) separation, 2) Vis detection, 3) UV detection, 4) fluorescence detection (FLD), 5) bioassay for effect-directed analysis (EDA), 6) heart-cut trapping/desalting/elution to reversed phase high-performance liquid chromatography (RP-HPLC) separation, 7) photodiode array (PDA) and 8) mass spectrometry (MS) detection. For the first time, the hyphenation exploited online analyte trapping to desalt the eluted bioactive zone from the plate containing highly salted bioassay media. Subsequent valve switching guided the trapped analyte(s) to the main column, followed by multiple detection. As proof-of-principle, cinnamon samples were analyzed by NP-HPTLC−UV/Vis/FLD−EDA−RP-HPLC−PDA−MS, whereby a bioactive zone was separated into two distinct peaks detected by PDA and MS to be 2-methoxy cinnamaldehyde and cinnamaldehyde. The developed 8D hyphenation is applicable for routine, allowing the non-target high-throughput screening of complex samples for individual bioactive compounds.
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The covalent diamantyl (C28H38) and oxadiamantyl (C26H34O2) dimers are stabilized by London dispersion attractions between the dimer moieties. Their solid-state and gas-phase structures were studied ...using a multitechnique approach, including single-crystal X-ray diffraction (XRD), gas-phase electron diffraction (GED), a combined GED/microwave (MW) spectroscopy study, and quantum chemical calculations. The inclusion of medium-range electron correlation as well as the London dispersion energy in density functional theory is essential to reproduce the experimental geometries. The conformational dynamics computed for C26H34O2 agree well with solution NMR data and help in the assignment of the gas-phase MW data to individual diastereomers. Both in the solid state and the gas phase the central C–C bond is of similar length for the diamantyl XRD, 1.642(2) Å; GED, 1.630(5) Å and the oxadiamantyl dimers XRD, 1.643(1) Å; GED, 1.632(9) Å; GED+MW, 1.632(5) Å, despite the presence of two oxygen atoms. Out of a larger series of quantum chemical computations, the best match with the experimental reference data is achieved with the PBEh-3c, PBE0-D3, PBE0, B3PW91-D3, and M06-2X approaches. This is the first gas-phase confirmation that the markedly elongated C–C bond is an intrinsic feature of the molecule and that crystal packing effects have only a minor influence.
The LiCl-mediated Mg-insertion in the presence of ZnCl2 allows an efficient synthesis of adamantylzinc reagents starting from the corresponding functionalized tertiary bromides. The highly reactive ...adamantylzinc species readily undergo a broad variety of functionalizations such as Negishi cross-couplings, Cu(I)-catalyzed acylations and allylations, and 1,4-addition reactions leading to the expected products in excellent yields. Furthermore, the adamantyl moiety could be introduced as α-substituent in terthiophene, increasing its solubility due to the higher lipophilicity and the prevention of π-stacking.
•Experimental and theoretical analysis of the anomalous Hall effect in MnGa thin films.•DFT calculations were performed to determine the intrinsic Berry curvature.•Intrinsic Berry curvature results ...in an anomalous Hall conductivity of 127(Ωcm)−1.•Side-jump contribution can be enhanced by the thermal activation mechanisms.
We report on resistivity and Hall effect in MnGa thin films grown by molecular beam epitaxy on GaAs substrates. Highly (111)-textured MnGa film with L10 structure exhibits hard magnetic properties with coercivities as high as 20kOe and spin disorder mechanisms contributing to the Hall conductivity at room temperature. Density functional theory calculations were performed to determine the intrinsic Berry curvature in the momentum space with chiral spin structure that results in an anomalous Hall conductivity of 127(Ωcm)−1 comparable to that measured at low temperature. In addition to residual and side-jump contributions, which are enhanced by thermal activation, both anomalous Hall conductivity and Hall angle increase between 100K and room temperature. The present results reinforce the potential of Mn-Ga system for developing Hall effect-based spintronic devices.
Circular RNAs (circRNAs) are a class of noncoding RNAs, generated from pre-mRNAs by circular splicing of exons and functionally largely uncharacterized. Here we report on the design, expression, and ...characterization of artificial circRNAs that act as protein sponges, specifically binding and functionally inactivating hnRNP (heterogeneous nuclear ribonucleoprotein) L. HnRNP L regulates alternative splicing, depending on short CA-rich RNA elements. We demonstrate that designer hnRNP L-sponge circRNAs with CA-repeat or CA-rich sequence clusters can efficiently and specifically modulate splicing-regulatory networks in mammalian cells, including alternative splicing patterns and the cellular distribution of a splicing factor. This new strategy can in principle be applied to any RNA-binding protein, opening up new therapeutic strategies in molecular medicine.
The recent development of diffraction-unlimited far-field fluorescence microscopy has overcome the classical resolution limit of ~250 nm of conventional light microscopy by about a factor of ten. The ...improved resolution, however, reveals not only biological structures at an unprecedented resolution, but is also susceptible to sample drift on a much finer scale than previously relevant. Without correction, sample drift leads to smeared images with decreased resolution, and in the worst case to misinterpretation of the imaged structures. This poses a problem especially for techniques such as Fluorescence Photoactivation Localization Microscopy (FPALM/PALM) or Stochastic Optical Reconstruction Microscopy (STORM), which often require minutes recording time. Here we discuss an approach that corrects for three-dimensional (3D) drift in images of fixed samples without the requirement for fiduciary markers or instrument modifications. Drift is determined by calculating the spatial cross-correlation function between subsets of localized particles imaged at different times. Correction down to ~5 nm precision is achieved despite the fact that different molecules are imaged in each frame. We demonstrate the performance of our drift correction algorithm with different simulated structures and analyze its dependence on particle density and localization precision. By imaging mitochondria with Biplane FPALM we show our algorithm's feasibility in a practical application.
An improved method to retrieve electron density profiles from Global Positioning System (GPS) radio occultation (RO) data is presented and applied to Constellation Observing System for Meteorology, ...Ionosphere, and Climate (COSMIC) observations. The improved inversion uses a monthly grid of COSMIC F region peak densities (NmF2), which are obtained via the standard Abel inversion, to aid the Abel inversion by providing information on the horizontal gradients in the ionosphere. This lessens the impact of ionospheric gradients on the retrieval of GPS RO electron density profiles, reducing the dominant error source in the standard Abel inversion. Results are presented that demonstrate the NmF2 aided retrieval significantly improves the quality of the COSMIC electron density profiles. Improvements are most notable at E region altitudes, where the improved inversion reduces the artificial plasma cave that is generated by the Abel inversion spherical symmetry assumption at low latitudes during the daytime. Occurrence of unphysical negative electron densities at E region altitudes is also reduced. Furthermore, the NmF2 aided inversion has a positive impact at F region altitudes, where it results in a more distinct equatorial ionization anomaly. COSMIC electron density profiles inverted using our new approach are currently available through the University Corporation for Atmospheric Research COSMIC Data Analysis and Archive Center. Owing to the significant improvement in the results, COSMIC data users are encouraged to use electron density profiles based on the improved inversion rather than those inverted by the standard Abel inversion.
Key Points
Develop new inversion for COSMIC electron density profiles
New inversion reduces the impact of horizontal gradients on the Abel inversion
Inversion improves results in the E and F region ionosphere
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