Notes

Growing current software along with making it possible for your analysis of bigger unchanged samples by means of a 6 millimeters CMP-NMR probe.
Developing efficient Pt-based electrocatalysts for the methanol oxidation reaction (MOR) is of pivotal importance for large-scale application of direct methanol fuel cells (DMFCs), but Pt suffers from severe deactivation brought by the carbonaceous intermediates such as CO. Here, we demonstrate the formation of a bismuth oxyhydroxide (BiO x (OH) y )-Pt inverse interface via electrochemical reconstruction for enhanced methanol oxidation. By combining density functional theory calculations, X-ray absorption spectroscopy, ambient pressure X-ray photoelectron spectroscopy, and electrochemical characterizations, we reveal that the BiO x (OH) y -Pt inverse interface can induce the electron deficiency of neighboring Pt; this would result in weakened CO adsorption and strengthened OH adsorption, thereby facilitating the removal of the poisonous intermediates and ensuring the high activity and good stability of Pt2Bi sample. This work provides a comprehensive understanding of the inverse interface structure and deep insight into the active sites for MOR, offering great opportunities for rational fabrication of efficient electrocatalysts for DMFCs.Oligomers of 5-amino-N-acylanthranilic acid, previously unknown aromatic oligoamides that cannot be obtained with known amide coupling methods, are synthesized based on a new, highly efficient amide-bond formation strategy that takes advantage of the ring-opening of benzoxazinone derivatives. These oligoamides offer multiple backbone NH groups as H-bond donors which, in the presence of iodide or chloride ion, are convergently arranged and H-bonded, which enforces a folded, crescent conformation. These aromatic oligoamides provide a versatile platform based on which anion-dependent foldamers, or anion binders with tunable affinity and specificity, are being constructed.The reaction mechanism of biomass decomposition by xylanases remains the subject of debate. To clarify the mechanism we investigated the glycosylation step of GH11 xylanase, an enzyme that catalyzes the hydrolysis of lignocellulosic hemicellulose (xylan). Making use of a recent neutron crystal structure, which revealed the protonation states of relevant residues, we used ab initio quantum mechanics/molecular mechanics (QM/MM) calculations to determine the detailed reaction mechanism of the glycosylation step. In particular, our focus is on the controversial question of whether or not an oxocarbenium ion intermediate is formed on the reaction pathway. The calculations support the validity of a basic retaining mechanism within a double-displacement scheme. The estimated free energy barrier of this reaction is ∼18 kcal/mol with QM/MM-CCSD(T)/6-31(+)G**//MP2/6-31+G**/AMBER calculations, and the rate-determining step of the glycosylation is scission of the glycosidic bond after proton transfer from the acidic Glu177. The estimated lifetime of the oxocarbenium ion intermediate (on the order of tens of ps) and the secondary kinetic isotope effect suggest that there is no accumulation of this intermediate on the reaction path, although the intermediate can be transiently formed. In the enzyme-substrate (ES) complex, the carbohydrate structure of the xylose residue at the -1 subsite has a rather distorted (skewed) geometry, and this xylose unit at the active site has an apparent half-chair conformation when the oxocarbenium ion intermediate is formed. The major catalytic role of the protein environment is to orient residues that take part in the initial proton transfer. Because of a fine alignment of catalytic residues, the enzyme can accelerate the glycosylation reaction without paying a reorganization energy penalty.A selenium-catalyzed trifluoromethylthiolation/[2,3]-sigmatropic rearrangement of tertiary allylic and propargylic alcohols which could provide straightforward and facile access to trifluoromethyl sulfoxides was developed. Various allylic and allenic trifluoromethyl sulfoxides were obtained with moderate to excellent yields. Meanwhile, a Lewis acid mediated trifluoromethylthiolation/1,2-rearrangement to synthesize β-SCF3 carbonyl compounds was also accomplished. These two tandem reactions feature with mild reaction conditions and metal-free. During these two reactions, the chemoselectivity of electrophilic trifluoromethylthiolation was revealed.There is an urgent need to develop new efficacious antimalarials to address the emerging drug-resistant clinical cases. Our previous phenotypic screening identified styrylquinoline UCF501 as a promising antimalarial compound. To optimize UCF501, we herein report a detailed structure-activity relationship study of 2-arylvinylquinolines, leading to the discovery of potent, low nanomolar antiplasmodial compounds against a Plasmodium falciparum CQ-resistant Dd2 strain, with excellent selectivity profiles (resistance index 200). Several metabolically stable 2-arylvinylquinolines are identified as fast-acting agents that kill asexual blood-stage parasites at the trophozoite phase, and the most promising compound 24 also demonstrates transmission blocking potential. Additionally, the monophosphate salt of 24 exhibits excellent in vivo antimalarial efficacy in the murine model without noticeable toxicity. Thus, the 2-arylvinylquinolines represent a promising class of antimalarial drug leads.An ethylammonium-templated indium sulfide, [CH3CH2NH3]6In8S15 (InS-2), featuring anionic layers perforated with large, 24-membered rings that facilitate the accommodation of hydrated Sr2+ ions is reported. InS-2 exhibits an excellent adsorption performance toward Sr2+ with a top-ranked capacity (qm = 143.29 mg g-1), rapid kinetics, wide pH durability (3-14), β- and γ-radiation resistances, and a facile elution.Ultraviolet photodissociation (UVPD) has emerged as a useful technique for characterizing peptide, protein, and protein complex primary and secondary structure. 193 nm UVPD, specifically, enables extensive covalent fragmentation of the peptide backbone without the requirement of a specific side chain chromophore and with no precursor charge state dependence. We have modified a commercial quadrupole-ion mobility-time-of-flight (Q-IM-TOF) mass spectrometer to include 193 nm UVPD following ion mobility. Ion mobility (IM) is a gas-phase separation technique that enables separation of ions by their size, shape, and charge, providing an orthogonal dimension of separation to mass analysis. Following instrument modifications, we characterized the performance of, and information that could be generated from, this new setup using the model peptides substance P, melittin, and insulin chain B. this website These experiments show extensive fragmentation across the peptide backbone and a variety of ion types as expected from 193 nm UVPD. Additionally, y-2 ions (along with complementary a+2 and b+2 ions) N-terminal to proline were observed. Combining the IM separation and mobility gating capabilities with UVPD, we demonstrate the ability to accomplish both mass- and mobility-selection of bradykinin des-Arg9 and des-Arg1 peptides followed by complete sequence characterization by UVPD. The new capabilities of this modified instrument demonstrate the utility of combining IM with UVPD because isobaric species cannot be independently selected with a traditional quadrupole alone.The porphyrin macrocycle can stabilize a set of magnetic metal ions, thus introducing localized net spins near the center. However, it remains elusive but most desirable to introduce delocalized spins in porphyrins with wide implications, for example, for building correlated quantum spins. Here, we demonstrate that metal-free porphyrins host delocalized π-electron magnetism, as revealed by scanning probe microscopy and a different level of theory calculations. Our results demonstrate that engineering of π-electron topologies introduces a spin-polarized singlet state and delocalized net spins in metal-free porphyrins. In addition, the π-electron magnetism can be switched on/off via scanning tunneling microscope manipulation by tuning the interfacial charge transfer. Our results provide an effective way to precisely control the π-electron magnetism in metal-free porphyrins, which can be further extended to design new magnetic functionalities of porphyrin-based architectures.The rising demand for more and more specialized polyethylene represents a challenge for synthesis and analysis. The desired properties are dependent on the structure, but its elucidation is still intricate. For this purpose, we applied thermal analysis hyphenated to single photon ionization mass spectrometry (STA-SPI-MS). The melting and pyrolysis behavior of different types of polyethylene were tracked by DSC and mass loss. Crystallinity and melting point give hints about the branching but are also influenced by the molecular weight distribution. The evolving gas analysis patterns obtained by SPI-MS however, contain specific molecular information about the samples. Shifts in the summed spectra, which can be clearly observed with our technique, result from differently favored degradation reactions due to the respective structure. Pyrolysis gas chromatography mass spectrometry (Py-GC-EI-MS) was used to support the assignment of pyrolysis products. Principal component analysis was successfully applied to reduce the complexity of data and find suitable markers. The obtained grouping is based on the molecular fingerprint of the samples and is strongly influenced by short-chain branching. Short and medium alkenes and dienes have the strongest impact on the first four principal components. Thus, two marker ratios could be defined, which also give a comprehensible and robust grouping. Butene and pentene were the most abundant signals in our set of samples. With STA-PI-MS, a broad range of pyrolysis products can be measured at the same time, possibly extending the range for quantifiable short-chain branches to more than six carbon atoms for PE. Unfortunately, no clear trend between long-chain branching and any grouping was observed. The quite universal and soft single photon ionization enables access to many different compound classes and hence other polymers can be studied.Electricity demand for room air conditioners (ACs) has been growing significantly in China in response to rapid economic development and mounting impacts of climate change. In this study, we use the bottom-up model approach to predict the penetration rate of room ACs in the residential building sector of China at the provincial level, with the consideration of the urban-rural heterogeneity. In addition, we assess co-benefits associated with enhanced energy efficiency improvement of AC systems and the adoption of low-global-warming-potential (low-GWP) refrigerants in AC systems. The results indicate that the stock of room ACs in China grows from 568 million units in 2015 to 997 million units in 2030 and 1.1 billion units in 2050. The annual electricity saving from switching to more efficient ACs using low-GWP refrigerants is estimated at almost 1000 TWh in 2050 when taking account of the full technical energy efficiency potential. This is equivalent to approximately 4% of the expected total energy consumption in the Chinese building sector in 2050 or the avoidance of 284 new coal-fired power plants of 500 MW each. The cumulative CO2eq mitigation associated with both the electricity savings and the substitution of high-GWP refrigerants makes up 2.6% of total business-as-usual CO2eq emissions in China over the period 2020 to 2050. The transition toward the uptake of low-GWP refrigerants is as vital as the energy efficiency improvement of new room ACs, which can help and accelerate the ultimate goal of building a low-carbon society in China.
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