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941.
Separation science is an art of obtaining adequate resolution of the desired compounds in minimum time, and with minimum effort in terms of sample preparation and data evaluation. In LC, where selectivity is a main driving force for separation, the availability of different separation modes capable of operating at high flow rates is a way to make combined optimal use of selectivity, efficiency, and speed. The separation of polar and hydrophilic compounds is problematic in RP LC due to the poor retention. Hydrophilic interaction liquid chromatography (HILIC) is a more straightforward separation mode to address this problem. Herein, it is shown that separations in HILIC mode are equally efficient as for RP, providing a potential for very fast separations on short columns. This is not only facilitated by the low viscosity of the mobile phase compositions used, compared to typical RP eluents, but also due to higher column permeability. To exemplify this, baseline separations of uracil and cytosine are shown in less than 4 s and of Tamiflu and its main metabolite in less than 40 s, both under isocratic conditions. HILIC must therefore be considered having potential for high throughput purposes, and being an attractive candidate as the second separation dimension in 2-D HPLC. 相似文献
942.
Dr. Assma Benkada Felix Hartmann Dr. Tobias A. Engesser Dr. Sylvio Indris Dr. Tatiana Zinkevich Prof. Dr. Christian Näther Henning Lühmann Dr. Helge Reinsch Prof. Dr. Stefan Adams Prof. Dr. Wolfgang Bensch 《Chemistry (Weinheim an der Bergstrasse, Germany)》2023,29(1):e202202318
A highly unusual solid-state epitaxy-induced phase transformation of Na4SnS4 ⋅ 14H2O ( I ) into Na4Sn2S6 ⋅ 5H2O ( II ) occurs at room temperature. Ab initio molecular dynamics (AIMD) simulations indicate an internal acid-base reaction to form [SnS3SH]3− which condensates to [Sn2S6]4−. The reaction involves a complex sequence of O−H bond cleavage, S2− protonation, Sn−S bond formation and diffusion of various species while preserving the crystal morphology. In situ Raman and IR spectroscopy evidence the formation of [Sn2S6]4−. DFT calculations allowed assignment of all bands appearing during the transformation. X-ray diffraction and in situ 1H NMR demonstrate a transformation within several days and yield a reaction turnover of ≈0.38 %/h. AIMD and experimental ionic conductivity data closely follow a Vogel-Fulcher-Tammann type T dependence with D(Na)=6×10−14 m2 s−1 at T=300 K with values increasing by three orders of magnitude from −20 to +25 °C. 相似文献
943.
Prof. Dr. Luke R. Odell Dr. Bobo Skillinghaug Dr. Christof Matt Dr. Peng Wu Tobias Koolmeister Dr. Matthieu Desroses Dr. Sabin Llona-Minguez Dr. Olov Wallner Prof. Dr. Thomas Helleday Dr. Martin Scobie 《European journal of organic chemistry》2023,26(29):e202300725
Herein, we report on the discovery and development of novel cascade N−N bond forming reactions for the synthesis of rare indazole acetic acid scaffolds. This approach allows for convenient synthesis of three distinct indazole acetic acid derivatives (unsubstituted, hydroxy, and alkoxy) by heating 3-amino-3-(2-nitroaryl)propanoic acids with an appropriate nucleophile/solvent under basic conditions. The reaction tolerates a range of functional groups and electronic effects and, in total, 23 novel indazole acetic acids were synthesized and characterized. This work offers a valuable strategy for the synthesis of useful scaffolds for drug discovery programs. 相似文献
944.
Dr. Zheng Zhou Matthew Pennachio Dr. Zheng Wei Maxi L. Heldner Prof. Dr. Marina A. Petrukhina Dr. Tobias A. Schaub 《European journal of organic chemistry》2023,26(14):e202300168
A small macrocycle comprising ether-bridged naphthyl units was prepared in a two-step synthesis. Single-crystal X-ray diffraction of two polymorphs are reported, one of which showed multiple C−H⋅⋅⋅πnaphthyl interactions of a solvent molecule in the cavity of the macrocycle. Chemical reduction led to C−O bond cleavages accompanied by a Z/E isomerization. The resulting twofold negatively charged (E)-1,2-bis(2-naphthyl)ethylene fragment was isolated as its potassium salts. Electronic characterization revealed a singlet ground state, and a marked distortion of the central ethylene unit was observed upon electron uptake. 相似文献
945.
Sven Froitzheim Dr. Jannik Junge Christopher Barnehl Dr. Tobias A. Engesser Dr. Jan Krahmer Prof. Dr. Christian Näther Prof. Dr. Felix Tuczek 《欧洲无机化学杂志》2023,26(33):e202300280
Series of linear tridentate PNPhPR-ligands (R=Me, Et, Pln, Ph, Cyp, iPr, Cy, tBu) and molybdenum tricarbonyl complexes [Mo(CO)3PNPhPR] (R=Ph, Et, Cyp, iPr, Cy,) were synthesized and characterized using NMR-, IR-, and Raman spectroscopy as well as X-ray crystallography. The influence of the different phosphine donor groups of the PNPhPR ligands on the bonding and activation of CO ligands is investigated. Importantly, all complexes are found to adopt a fac geometry, both in solution and in the solid state. This is in contrast to analogous complexes supported by PNHP ligands. DFT calculations reveal that the phenyl ring at the central amine function is the cause of the preferred geometry, hindering isomerization to a mer geometry. 相似文献
946.
Tobias Hedtke Mathias Mende Heiko Steenbock Jürgen Brinckmann Matthias Menzel Wolfgang Hoehenwarter Markus Pietzsch Thomas Groth Christian E. H. Schmelzer 《Macromolecular bioscience》2023,23(11):2300203
Elastin is an essential extracellular matrix protein that enables tissues and organs such as arteries, lungs, and skin, which undergo continuous deformation, to stretch and recoil. Here, an approach to fabricating artificial elastin with close-to-native molecular and mechanical characteristics is described. Recombinantly produced tropoelastin are polymerized through coacervation and allysine-mediated cross-linking induced by pyrroloquinoline quinone (PQQ). A technique that allows the recovery and repeated use of PQQ for protein cross-linking by covalent attachment to magnetic Sepharose beads is developed. The produced material closely resembles natural elastin in its molecular, biochemical, and mechanical properties, enabled by the occurrence of the cross-linking amino acids desmosine, isodesmosine, and merodesmosine. It possesses elevated resistance against tryptic proteolysis, and its Young's modulus ranging between 1 and 2 MPa is similar to that of natural elastin. The approach described herein enables the engineering of mechanically resilient, elastin-like materials for biomedical applications. 相似文献
947.
948.
Amphiphilic block copolymers of the type poly(ethylenepropylene)-co-poly(ethyleneoxide) dramatically enhance the solubilisation efficiency of non-ionic surfactants in microemulsions that contain equal volumes of water in oil. Consequently, the length scale of the microstructure of such bicontinuous microemulsions is dramatically increased up to the order of a few 100 nm. In this paper, we show that this so-called efficiency boosting effect can also be applied to water-in-oil microemulsions with droplet microstructure. Such giant water-in-oil microemulsions would provide confined compartments in which chemical reactions of biological macromolecules can be performed on a single molecule level. With this motivation we investigated the phase behavior and the microstructure of oil-rich microemulsions containing D(2)O, n-decane(d22), C(10)E(4) and the amphiphilic block copolymer PEP5-PEO5 [poly(ethylenepropylene)-co-poly(ethyleneoxide), weight per block of 5000 g/ mol]. We found that 15 wt % of water can be solubilised by 5 wt % of surfactant and block copolymer when about 6 wt % of surfactant is replaced by the block copolymer. Small-angle-neutron-scattering experiments were performed to determine the length scales and microstructure topologies of the oil-rich microemulsions. To analyze the scattering data, we derived a novel form factor that also takes into account the scattering contribution of the hydrophobic part of the block copolymer molecules that reside in the surfactant shell. The quantitative analysis of the scattering data with this form factor shows that the radius of the largest droplets amounts up to 30 nm. The novel form factor also yielded qualitative information on the stretching of the polymer chains in dependence on the polymer surface density and the droplet radius. 相似文献
949.
Many experimental programs in chromatography involve the estimation of a second-order response surface. The paper focuses on the use of the methods of optimal experimental design to find efficient response surface designs. We give tables of the properties of designs with two, three and four factors. References are given to tables of designs and to SAS programs for their construction. 相似文献
950.
Krepelová A Reich T Sachs S Drebert J Bernhard G 《Journal of colloid and interface science》2008,319(1):40-47
To determine the influence of humic acid (HA), pH, and presence of atmospheric CO2 on the sorption of U(VI) onto kaolinite, the structure of the surface complexes was studied by U L III-edge extended X-ray absorption fine structure (EXAFS) spectroscopy. The best fits to the experimental EXAFS data were obtained by including two uranium coordination shells with two axial (O ax) and five equatorial (O eq) oxygen atoms at 1.77+/-0.02 and 2.34+/-0.02 A, respectively, and two coordination shells with one Al/Si atom each at 3.1 and 3.3 A. As in the case of the binary system U(VI)-kaolinite, uranium forms inner-sphere surface complexes by edge sharing with aluminum octahedra and/or silicon tetrahedra. HA and atmospheric CO2 as well as pH had no influence on the EXAFS structural parameters in the pH range of 5-8. Despite the presence of HA, U(VI) prefers to sorb directly onto kaolinite and not to HA that is bound to the clay surface. X-ray photoelectron spectroscopy (XPS) measurements of kaolinite particles that had been exposed to HA suspensions showed that significant parts of the kaolinite surface are not covered by HA. 相似文献