Floating supported bilayers (FSBs) are new systems which have emerged over the past few years to produce supported membrane mimics, where the bilayers remain associated with the substrate, but are cushioned from the substrates constraining influence by a large hydration layer. In this paper we describe a new approach to fabricating FSBs using a chemically grafted phospholipid layer as the support for the floating membrane. The grafted lipid layer was produced using a Langmuir-Schaeffer transfer of acryloyl-functionalized lipid onto a pre-prepared substrate, with AIBN-induced cross-polymerization to permanently bind the lipids in place. A bilayer of DSPC was then deposited onto this grafted monolayer using a combination of Langmuir-Blodgett and Langmuir-Schaeffer transfer. The resulting system was characterized by neutron reflection under two water contrasts, and we show that the new system shows a hydrating layer of approximately 17.5 A in the gel phase, which is comparable to previously described FSB systems. We provide evidence that the grafted substrate is reusable after cleaning and suggest that this greatly simplifies the fabrication and characterization of FSBs compared to previous methods. 相似文献
Crystallographic disorder, whether static or dynamic, can be detrimental to the physical and chemical stability, ease of crystallization and dissolution rate of an active pharmaceutical ingredient. Disorder can result in a loss of manufacturing control leading to batch-to-batch variability and can lengthen the process of structural characterization. The range of NMR active nuclei makes solid-state NMR a unique technique for gaining nucleus-specific information about crystallographic disorder. Here, we explore the use of high-field 35Cl solid-state NMR at 23.5 T to characterize both static and dynamic crystallographic disorder: specifically, dynamic disorder occurring in duloxetine hydrochloride ( 1 ), static disorder in promethazine hydrochloride ( 2 ), and trifluoperazine dihydrochloride ( 3 ). In all structures, the presence of crystallographic disorder was confirmed by 13C cross-polarization magic-angle spinning (CPMAS) NMR and supported by GIPAW-DFT calculations, and in the case of 3 , 1H solid-state NMR provided additional confirmation. Applying 35Cl solid-state NMR to these compounds, we show that higher magnetic fields are beneficial for resolving the crystallographic disorder in 1 and 3 , while broad spectral features were observed in 2 even at higher fields. Combining the data obtained from 1H, 13C, and 35Cl NMR, we show that 3 exhibits a unique case of disorder involving the +N−H hydrogen positions of the piperazinium ring, driving the chloride anions to occupy three distinct sites. 相似文献
We present a simple algorithm for robust and unsupervised peak detection by determining a noise threshold in isotopically resolved mass spectrometry data. Solving this problem will greatly reduce the subjective and time-consuming manual picking of mass spectral peaks and so will prove beneficial in many research applications. The Autopiquer approach uses autocorrelation to test for the presence of (isotopic) structure in overlapping windows across the spectrum. Within each window, a noise threshold is optimized to remove the most unstructured data, whilst keeping as much of the (isotopic) structure as possible. This algorithm has been successfully demonstrated for both peak detection and spectral compression on data from many different classes of mass spectrometer and for different sample types, and this approach should also be extendible to other types of data that contain regularly spaced discrete peaks.
The first syntheses of hybrid structures that lie between subphthalocyanines and subporphyrins are reported. The versatile single‐step synthetic method uses a preformed aminoisoindolene to provide the bridging methine unit and its substituent while trialkoxyborates simultaneously act as Lewis acid, template, and provider of the apical substituent. The selection of each component therefore allows for the controlled formation of diverse, differentially functionalized systems. The new hybrids are isolated as robust, pure materials that display intense absorption and emission in the mid‐visible region. The new compounds are further characterized in solution and solid state by variable‐temperature NMR spectroscopy and X‐ray crystallography, respectively. 相似文献
Podand‐type ligands are an interesting class of acyclic ligands which can form host–guest complexes with many transition metals and can undergo conformational changes. Organic phosphates are components of many biological molecules. A new route for the synthesis of phosphate esters with a retained six‐membered ring has been used to prepare 2,2′‐[benzene‐1,2‐diylbis(oxy)]bis(5,5‐dimethyl‐1,3,2‐dioxaphosphinane) 2,2′‐dioxide, C6H4{O[cyclo‐P(O)OCH2CMe2CH2O]}2 or C16H24O8P2, (1), 2‐[(2′‐hydroxybiphenyl‐2‐yl)oxy]‐5,5‐dimethyl‐1,3,2‐dioxaphosphinane 2‐oxide, [cyclo‐P(O)OCH2CMe2CH2O](2,2′‐OC6H4–C6H4OH), (2), and oxybis(5,5‐dimethyl‐1,3,2‐dioxaphosphinane) 2,2′‐dioxide, O[cyclo‐P(O)OCH2CMe2CH2O]2, (3). Compound (1) is novel, whereas the results for compounds (2) and (3) have been reported previously, but we record here our results for compound (3), which we find are more precise and accurate than those currently reported in the literature. In (1), two cyclo‐P(O)OCH2CMe2CH2O groups are linked through a catechol group. The conformations about the two catechol O atoms are quite different, viz. one C—C—O—P torsion angle is −169.11 (11)° and indicates a trans arrangement, whereas the other C—C—O—P torsion angle is 92.48 (16)°, showing a gauche conformation. Both six‐membered POCCCO rings have good chair‐shape conformations. In both the trans and gauche conformations, the catechol O atoms are in the axial sites and the short P=O bonds are equatorially bound. 相似文献
An instrumentally simple and cost-effective method for the direct analysis of methyl bromide in ambient air is described. The method is based on the separation of sample components by gas chromatography, the conversion of methyl bromide to methyl iodide by reaction with an inorganic iodide salt, and the detection of the methyl iodide thereby produced by an electron-capture detector. Of the 20 different inorganic salts investigated here for conversion of methyl bromide to methyl iodide, zinc iodide was found to provide the greatest conversion efficiency. In addition, zinc iodide was found to provide high conversion efficiency at a modest reaction temperature, thereby minimizing both the thermal decomposition of compounds within the reaction volume and the level of column bleed introduced to the detector. The reactions of several other brominated and chlorinated organic compounds with zinc iodide have also been characterized. The successful application of this instrument to the quantitative determination of methyl bromide in a local background air sample is then demonstrated. 相似文献
Aqueous dispersions of colloidal boehmite rods turn into strong gels when the concentration of (1–1) electrolyte concentrations becomes exceeds 50 mM. However, after addition of aluminium chlorohydrate (ACH) the rods remain stable up to salt concentrations as high as 2 M. Moreover the boehmite-ACH dispersions with an aspect ratio of 19 quickly separate into an isotropic and a liquid crystal nematic phase above a typical threshold concentration of 2 v/v%. It is known that ACH forms polynuclear cations at mild acidic conditions. The anomalous stability as encountered in these dispersions is explained by assuming that these hydrolyzed poly-cations cause a shift of the charge carrying surface. 相似文献
The 1s–2s energy interval in the muonium (μ+e−) atom has been measured by Doppler free two photon laser spectroscopy. A value of 2455528941.0(9.8) MHz has been obtained
in good agreement with quantum electrodynamics (QED). The muon-electron mass ratio can be extracted and is found to be 206.76838(17).
The measurement may also be interpreted as a determination of the muon-electron charge ratio as -1- 1.1(2.1)· 10−9. Corresponding measurements in deuterium using the same experimental setup confirmed the validity of the applied analysis
procedure.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献