A new family of three-legged piano stool structured organometallic compounds containing the fragment η5-cyclopentadienyl-ruthenium(II)/iron(II) has been synthesized to evaluate the existence of electronic metal to ligand charge transfer upon coordination of the novel benzodithiophene ligands (BDT), benzo[1,2-b;4,3-b′]dithiophen-2-carbonitrile (L1) and benzo[1,2-b;4,3-b′]dithiophen-2′nitro-2-carbonitrile (L2). All the compounds were characterized by 1H, 13C, 31P NMR, IR and UV-Vis. spectroscopies and their electrochemistry studied by cyclic voltammetry. The X-ray structures of [Ru(η5-C5H5)(PPh3)2(NCC10H5S2)][PF6] (1Ru), [Ru(η5-C5H5)(PPh3)2(NCC10H5S2)][CF3SO3] (1′Ru), [Ru(η5-C5H5)(DPPE)(NCC10H5S2)][PF6] 2Ru and [Fe(η5-C5H5)(DPPE)(NCC10H5S2)][PF6] (2Fe) were determined by X-ray diffraction showing centric crystallization on groups and P21/n, respectively.Quadratic hyperpolarizabilities (β) of some of the complexes (2Fe, 2Ru and 3Fe) have been determined by hyper-Rayleigh scattering (HRS) measurements at a fundamental wavelength of 1500 nm, to minimize the probability of fluorescence due to two-photon absorption and to reduce the effect of resonance enhancement, in order to estimate static β values. 相似文献
We present here a (67)Zn solid-state NMR investigation of Zn(2+) substituted rubredoxin. The sample has been prepared as both a dry powder and a frozen solution to determine the effects of static disorder on the NMR line shape. Low-temperature experiments have been performed at multiple fields to determine the relative contributions to the NMR line shape from the electric field gradient and the anisotropic shielding tensors. Finally we present the theoretical interpretation of the experimental results utilizing a combined quantum mechanical molecular mechanics (QM/MM) approach. Theory predicts a sizable contribution from anisotropic shielding as compared with previously examined model systems. This is in good agreement with the experimental data. 相似文献
Observations of a sample of poly(ethylene-co-octene)in a
polarizing optical microscope reveal peculiarities in its
crystallization behavior. When cooled from the melt to a fixed
crystallization temperature, at first a structure of diffuse
appearance with variations on the length scale of micrometers
forms rapidly. The transformation into the final semi-crystalline
state then proceeds in two ways, by a continuous change of the
inner structure of m-sized objects and by the growth of
spherulites. Time dependent small angle and wide angle X-ray
scattering experiments corroborate the occurrence of the two
crystallization mechanisms. Atomic force microscopy indicates that
the change of the inner structure of the preformed objects is due
to an in-filling of crystallites. 相似文献
The human complement hetero-trimeric C8αβγ (C8) protein assembly (~?150 kDa) is an important component of the membrane attack complex (MAC). C8 initiates membrane penetration and coordinates MAC pore formation. Here, we charted in detail the structural micro-heterogeneity within C8, purified from human plasma, combining high-resolution native mass spectrometry and (glyco)peptide-centric proteomics. The intact C8 proteoform profile revealed at least ~?20 co-occurring MS signals. Additionally, we employed ion exchange chromatography to separate purified C8 into four distinct fractions. Their native MS analysis revealed even more detailed structural micro-heterogeneity on C8. Subsequent peptide-centric analysis, by proteolytic digestion of C8 and LC-MS/MS, provided site-specific quantitative profiles of different types of C8 glycosylation. Combining all this data provides a detailed specification of co-occurring C8 proteoforms, including experimental evidence on N-glycosylation, C-mannosylation, and O-glycosylation. In addition to the known N-glycosylation sites, two more N-glycosylation sites were detected on C8. Additionally, we elucidated the stoichiometry of all C-mannosylation sites in all the thrombospondin-like (TSP) domains of C8α and C8β. Lastly, our data contain the first experimental evidence of O-linked glycans located on C8γ. Albeit low abundant, these O-glycans are the first PTMs ever detected on this subunit. By placing the observed PTMs in structural models of free C8 and C8 embedded in the MAC, it may be speculated that some of the newly identified modifications may play a role in the MAC formation.
This paper reviews some of our research on three classes of supra-molecular architectures which are generated via various combinations of molecular, macromolecular, and supramolecular chemistry. The ability of these supramolecular architectures to form liquid crystalline phases is determined by the shape of the self-assembled architecture and will be used to visualize it via various characterization techniques. The molecular design of selected examples of structural units containing taper-shaped exo-receptors and crown ether, oligooxyethylenic, and H-bonding based endo-receptors which self-assemble into cylindrical channel-like architectures via principles resembling those of tobacco mosaic virus (TMV), of macrocyclics which self-assemble into supramolecular rigid “rodlike” architectures and of hyperbranched polymers which self-assemble.into a willowlike architecture will be discussed. In the case of TMV-like supramolecular architectures, a comparison between various supramolecular(generated via H-bonding, ionic, and electrostatic interactions) and molecular “polymer backbones” will be made. The present state of the art of the engineering of these supramolecular architectures and some possible novel material functions derived from them will be briefly mentioned. 相似文献
This paper describes several successful cost-effective attempts to couple capillary electrophoresis (CE) and mass spectrometry (MS) without make-up flow or nebulizing gas. An in-depth analysis of several interfaces using conductive spray tips was performed as well as an easy-to-prepare T-junction with direct electrode contact, the latter being the most robust interface. No coating is necessary and the spray voltage is applied through a gold wire positioned at the gap between the separation and spray capillaries. The T-junction interface is made by puncturing a small piece of transparent rubber. The on-line preconcentration CE-MS system allows immunoassay sensitivity, as is demonstrated by a calibration plot in the picomolar range for angiotensin II and gonadorelin. It also shows good reproducibility and has the ability of excellent automation. The secure electrical contact gives a constant spray quality, even with 100% aqueous separation buffers. The described setup has a wide applicability as is demonstrated by the analysis of larger peptides, such as insulin and cytochrome c. Detailed information is given on critical factors in the preparation of the described interfaces. 相似文献