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This study outlines the use of mid-infrared (MIR) spectroscopy combined with principal component analysis (PCA) and linear discriminant analysis (LDA) for the varietal classification of commercial red and white table wines. Three red varieties (Cabernet Sauvignon, Shiraz and Merlot) and four white varieties (Chardonnay, Riesling, Sauvignon Blanc and Viognier) were sourced from different wine regions in Australia. Wine samples were scanned in transmission on a FOSS WineScan FT 120 from wave numbers 926 to 5012 cm−1. All samples were sourced from the 2006 vintage and had not been blended with any other variety or wine from other regions. Spectral data were reduced to a small number of principal components (PCs) and LDA was then performed to successfully separate the wines into the different varieties. To test the robustness of the LDA models developed for the red wines, a set of red wines scanned in 2005 were used. Correct classification of over 95% was achieved for the validation set.  相似文献
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Gibbilimbols A-D (1-4) were synthesized in 32-49% yield over four steps from commercially available starting materials. A copper-catalyzed coupling of 4-methoxyphenylmagnesium bromide with various unsaturated alkyl bromides was the key step in assembling the (long-chain alkyl)phenol skeleton.  相似文献
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Indolizine, pyrrolone, and indolizinone heterocycles are easily accessed via the Pt(II)-catalyzed cycloisomerization or a tandem cyclization/1,2-migration of pyridine propargylic alcohols and derivatives. This method provides an efficient synthesis of highly functionalized heterocycles from readily available substrates. [reaction: see text]  相似文献
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Direct analysis of proteins adsorbed onto the surface of nylon membranes has been performed at the picomole level by matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS). Nylon-66 and positive charge-modified nylon (Zetabind) membranes fixed to MALDI probe tips were successfully employed to analyze picomole quantities of sample that were adsorbed onto these inert supports prior to adding a matrix-containing solution. Proteins and peptides are readily solubilized from these types of membrane with conventional matrix solvents and cocrystallize with the matrix on the membrane surface. Because solubilization of membrane-adsorbed protein is necessary for successful sample preparation, nylon membranes are more suitable for use with MALDI-MS than other protein transfer membranes such as polyvinylidene difluoride or nitrocellulose. When compared to samples prepared conventionally, no apparent loss of sensitivity or resolution is observed when analysis by MALDI-MS is performed from nylon-66 or positive charge-modified nylon membranes. Detection limits and resolution are not apparently affected by the membrane immobilization/washing procedure, and no change in the mass accuracy is observed when analysis is performed on the nylon surface. However, there is a time shift (increase) in ion flight time when analysis by MALDI-time-of-flight-MS is performed directly from the membrane fixed to the probe tip (about 200 ns for an ion of mass 379.3). To maintain mass accuracy, the use of internal standards or external calibration performed on a membrane support was necessary. The immobilization of proteins on nylon membranes can be used to facilitate removal of water-soluble contaminants because the sample is retained when the membrane is immersed in water prior to adding the matrix solution. The feasibility of performing both chemical and enzymatic modifications of proteins adsorbed onto inert nylon supports prior to analysis by MALDi-MS is also demonstrated.  相似文献
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The ion/molecule reaction of the tolyl cation with dimethyl ether has been investigated using triple quadrupole mass spectrometry. Three isomers with [C7H7]+ composition, the 3-tolyl, benzyl, and tropylium cations, were individually selected and reacted with dimethyl ether at a pressure of 1 mtorr in the second quadrupole (Q2) collision cell. Only the tolyl ion reacted to yield a methoxylated product ion peak at m/z 122. This reaction product having m/z 122 is postulated to be identical in structure with the molecular ion of 3-methyl anisole, as supported by thermochemical data and the similarity of the collision induced dissociation (CID) daughter ion mass spectra of the product ion and the molecular ion of authentic 3-methyl anisole. The daughter ion mass spectra of the three [C7H7]+ isomers during CID, by using a triple quadrupole mass spectrometer, are nearly identical; on the other hand, the analytical approach based on the ion/molecule reaction with dimethyl ether clearly exhibits distinct gas-phase chemistry reflecting structural differences among the isomers. Sot  相似文献
7.
A metal-assembled homotrimeric coiled coil based on the GCN4-p1 sequence has been designed that noncovalently binds hexafluorobenzene and other similar ligands in a hydrophobic cavity, created by making the core substitution Asn16Ala ([Fe(bpyGCN4-N16A)3]2+). The KD of binding of hexafluorobenzene with [Fe(bpyGCN4-N16A)3]2+ was observed to be 1.1(9) x 10(-4) M by diffusion NMR experiments. A control coiled coil with the core substitution Asn16Val ([Fe(bpyGCN4-N16V)3]2+) exhibited a significantly weaker association with hexafluorobenzene, providing evidence that even in the absence of structural data, benzene-like ligands bind in the cavity created by the Asn16Ala substitution. 19F NMR was employed to observe hexafluorobenzene binding and to monitor titrations with competing hydrophobic and polar ligands similar in size and shape to hexafluorobenzene. All hydrophobic ligands bound with greater affinity than the polar ligands in the hydrophobic core, although the cavity seems to be somewhat flexible in terms of the sizes of molecules it can accommodate. Thus 19F NMR has proved to be a useful spectral tool to probe molecular recognition in a hydrophobic cavity of a metal-assembled coiled coil.  相似文献
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Metal ions serve many purposes in natural proteins, from the stabilization of tertiary structure to the direction of protein folding to crucial roles in electron transfer and catalysis. There is considerable interest in creating metal binding sites in designed proteins to understand the structural role of metal ions and to design new metalloproteins with useful functions. The de novo design of metalloproteins and the role of metals in the folding of designed proteins are reviewed here, with particular focus on the design, folding, and activities of the [M(bpy-peptide)(3)](2+) structure. This maquette is constructed by the covalent attachment of 2,2'-bipyridine to the N-termini of amphiphilic peptides, and it is assembled into a folded trimeric coiled coil by the addition of a six-coordinate transition metal ion and the resulting hydrophobic collapse of the peptides. The [M(bpy-peptide)(3)](2+) structure has been employed in diverse applications, ranging from electron transfer pathway studies to the study of optimal hydrophobic packing in a virtual library to the construction of receptors and biosensors.  相似文献
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Several heterocycles such as furanones, pyrrolones, and indolizines, which are of pharmacological importance, are easily accessed via the Pt(II)-catalyzed heterocyclization/1,2-migration of propargylic ketols or hydroxy imine derivatives. This method sidesteps the challenges of traditional heteroaromatic oxygenation strategies such as regioselectivity and functional group tolerance in the syntheses of these heterocycles.  相似文献
10.
The Ru(II)-Pt(II) supramolecular complex, [(Ph(2)phen)(2)Ru(dpp)PtCl(2)](2+), displays a new mechanism for DNA modification: photobinding through a (3)MLCT excited state. Gel shift analysis, selective DNA precipitation, and DNA melting point experiments support efficient covalent DNA binding following visible light excitation.  相似文献
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