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51.
Wai Keen Chung Ying Hou Melissa Holstein Alexander Freed George I. Makhatadze Steven M. Cramer 《Journal of chromatography. A》2010,1217(2):191-198
A library of cold shock protein B mutant variants was employed to examine differences in protein binding behavior in ion exchange and multimodal chromatography. Single site mutations introduced at charged amino acids on the protein surface resulted in a homologous protein set with varying charge density and distribution. The retention times of the mutants varied significantly during linear gradient chromatography in both systems. The majority of the proteins were more strongly retained on the multimodal cation exchange resin as compared to the traditional cation exchanger. Further, the elution order of the mutants on the multimodal resin was different from that obtained with the ion exchanger. Quantitative structure–property relationship models generated using a support vector regression technique were shown to provide good predictions for the retention times of protein mutants on the multimodal resin. A coarse-grained ligand docking package was employed to examine the various interactions between the proteins and ligands in free solution. The multimodal ligand was shown to utilize multiple interaction types to achieve stronger retention on the protein surface. The use of this protein library in concert with the qualitative and quantitative analyses presented in this paper provides an improved understanding of protein behavior in multimodal chromatographic systems. 相似文献
52.
MF Kuehnel P Holstein M Kliche J Krüger S Matthies D Nitsch J Schutt M Sparenberg D Lentz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(34):10701-10714
The hydrodefluorination (HDF) of fluoroalkenes in the presence of a variety of titanium catalysts was studied with respect to scope, selectivity, and mechanism. Optimization revealed that the catalyst requires low steric bulk and high electron density; secondary silanes serve as the preferred hydride source. A broad range of substrates yield partially fluorinated alkenes, such as previously unknown (Z)-1,2-(difluorovinyl)ferrocene. Mechanistic studies indicate a titanium(III) hydride as the active species, which forms a titanium(III) fluoride by H/F exchange with the substrate. The HDF step can follow both an insertion/elimination and a σ-bond metathesis mechanism; the E/Z selectivity is controlled by the substrate. The catalysts' ineffieciency towards fluoroallenes was rationalized by studying their reactivity towards Group?6 hydride complexes. 相似文献
53.
Matthias Hardy Niklas Struch Julian J. Holstein Gregor Schnakenburg Norbert Wagner Marianne Engeser Johannes Beck Guido H. Clever Arne Lützen 《Angewandte Chemie (International ed. in English)》2020,59(8):3195-3200
Two new heterobimetallic cages, a trigonal‐bipyramidal and a cubic one, were assembled from the same mononuclear metalloligand by adopting the molecular library approach, using iron(II) and palladium(II) building blocks. The ligand system was designed to readily assemble through subcomponent self‐assembly. It allowed the introduction of steric strain at the iron(II) centres, which stabilizes its paramagnetic high‐spin state. This steric strain was utilized to drive dynamic complex‐to‐complex transformations with both the metalloligand and heterobimetallic cages. Addition of sterically less crowded subcomponents as a chemical stimulus transformed all complexes to their previously reported low‐spin analogues. The metalloligand and bipyramid incorporated the new building block more readily than the cubic cage, probably because the geometric structure of the sterically crowded metalloligand favours the cube formation. Furthermore it was possible to provoke structural transformations upon addition of more favourable chelating ligands, converting the cubic structures into bipyramidal ones. 相似文献
54.
Ghadwal RS Azhakar R Pröpper K Holstein JJ Dittrich B Roesky HW 《Inorganic chemistry》2011,50(17):8502-8508
Reactions of N-heterocyclic carbene stabilized dichlorosilylene IPr·SiCl(2) (1) (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) with (η(5)-C(5)H(5))V(CO)(4), (η(5)-C(5)H(5))Co(CO)(2), and Fe(2)(CO)(9) afford dichlorosilylene complexes IPr·SiCl(2)·V(CO)(3)(η(5)-C(5)H(5)) (2), IPr·SiCl(2)·Co(CO)(η(5)-C(5)H(5)) (3), and IPr·SiCl(2)·Fe(CO)(4) (4), respectively. Complexes 2-4 are stable under an inert atmosphere, are soluble in common organic solvents, and have been characterized by elemental analysis and multinuclear ((1)H, (13)C, and (29)Si) NMR spectroscopy. Molecular structures of 2-4 have been determined by single crystal X-ray crystallographic studies and refined with nonspherical scattering factors. 相似文献
55.
56.
Resonance photoproduction is studied via the MIT bag model and comparison is made with a single quark transition SU(6)θ analysis. Correspondence is found between the two pictures. The bag model predictions are shown to be in good qualitative agreement with experiment; however, specific numerical results are rather model dependent and in general less successful. 相似文献
57.
Barry R. Holstein 《Czechoslovak Journal of Physics》2000,50(4):9-23
A brief introduction to the subject of chiral perturbation theory (Xpt) is presented, including a discussion of effective field theory and applications of Xpt in the arena of purely mesonic interactions as well as in the πN sector. 相似文献
58.
Singh AP Ghadwal RS Roesky HW Holstein JJ Dittrich B Demers JP Chevelkov V Lange A 《Chemical communications (Cambridge, England)》2012,48(61):7574-7576
An abnormal N-heterocyclic carbene (aNHC) has been used as a Lewis base to initiate dismutation of trichlorosilane. This report presents the reactivity differences of a normal N-heterocyclic carbene (NHC) versus aNHC with heavier group 14 elements. Three novel compounds (NHC)(2)·SiCl(2)H(2) (2), aNHC·SiCl(2)H(2) (3), and aNHC·GeCl(2) (4) have been synthesized and characterized by single crystal X-ray analysis, solid-state NMR and DFT calculations. 相似文献
59.
T. Holstein 《Molecular Crystals and Liquid Crystals》2013,570(1-4):235-252
A theoretical study of the properties of large polarons in quasi one-dimensional systems, including intrachain scattering by phonons, phonon emission and absorption processes. 相似文献
60.
Philipp M. Holstein Julian J. Holstein Eduardo C. Escudero-Adán Olivier Baudoin Antonio M. Echavarren 《Tetrahedron: Asymmetry》2017,28(10):1321-1329
The present study investigates a synthetically simple ferrocene derivatization of natural products and active pharmaceutical ingredients. Seven new crystal structures are analyzed together with 16 structures of ferrocene derivatives reported previously. In all cases, the unambiguous determination of the absolute structure was established from anomalous dispersion using the methods of Flack and Parsons. A comparison with other derivatization approaches shows the advantage of the described ferrocene derivatization for establishing the absolute configuration of novel compounds. 相似文献