Label-free electrochemical detection of DNA in blood serum via target-induced resolution of an electrode-bound DNA pseudoknot

We have demonstrated a fully covalent, signal-on E-DNA architecture based on the target-induced resolution of a DNA pseudokont. In the absence of target, the electrode-bound DNA probe adopts a pseudoknot conformation that segregates an attached methylene blue (MB) from the electrode. Upon target binding, the pseudoknot is resolved, leading to the formation of a single-stranded DNA element that supports electron transfer from the methylene blue to the electrode.

High resolution mass spectrometric alveolar proteomics: Identification of surfactant protein SP-A and SP-D modifications in proteinosis and cystic fibrosis patients

In the present study, one- and two-dimensional gel electrophoresis combined with high resolution Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS) have been applied as powerful approaches for the proteome analysis of surfactant proteins SP-A and SP-D, including identification of structurally modified and truncation forms, in bronchoalveolar lavage fluid from patients with cystic fibrosis, chronic bronchitis and pulmonary alveolar proteinosis. Highly sensitive micro preparation techniques were developed for matrix-assisted laser desorption/ionization (MALDI) FT-ICR MS analysis which provided the identification of surfactant proteins at very low levels. Owing to the high resolution, FT-ICR MS was found to provide substantial advantages for the structural identification of surfactant proteins from complex biological matrices with high mass determination accuracy. Several protein bands corresponding to SP-A and SP-D were identified by MALDI-FT-ICR MS after electrophoretic separation by one- and two-dimensional gel electrophoresis, and provided the identification of structural modifications (hydroxy-proline) and degradation products.

Determination of ethenzamide and acetoaminophen in quaternary powdered samples by near infrared spectroscopy and searching combination moving window partial least squares algorithm: effects of spectral resolution and signal-to-noise ratio

The present study reports an application of the searching combination moving window partial least squares (SCMWPLS) algorithm to the determination of ethenzamide and acetoaminophen in quaternary powdered samples by near infrared (NIR) spectroscopy. Another purpose of the study was to examine the instrumentation effects of spectral resolution and signal-to-noise ratio of the Buchi NIRLab N-200 FT-NIR spectrometer equipped with an InGaAs detector. The informative spectral intervals of NIR spectra of a series of quaternary powdered mixture samples were first located for ethenzamide and acetoaminophen by use of moving window partial least squares regression (MWPLSR). Then, these located spectral intervals were further optimised by SCMWPLS for subsequent partial least squares (PLS) model development. The improved results are attributed to both the less complex PLS models and to higher accuracy of predicted concentrations of ethenzamide and acetoaminophen in the optimised informative spectral intervals that are featured by NIR bands. At the same time, SCMWPLS is also demonstrated as a viable route for wavelength selection.

Capillary liquid chromatographic-high-resolution mass spectrometric analysis of ribonucleotides

A method of capillary HPLC-high-resolution MS was developed for the trace analysis of ATP, GTP, dATP and dGTP Dimethylhexylamine (DMHA) was used as ion-pairing agent for the HPLC retention and separation of the nucleotides and positive ion electrospray time-of-flight MS was used for the detection. The application of capillary HPLC allowed minimal usage of DMHA while providing excellent peak retention and resolution, which significantly reduced the ion suppression in electrospray ionization-MS analysis and thus increased the sensitivity. Adduct ions of nucleotides and DMHA were used as quantitative ions in order to achieve the best sensitivity. DMHA concentration at 5 mM in the aqueous mobile phase at pH 7 was found to be the optimal conditions for the C Is capillary column. The method was applied to determine ATP level in cultured C6 glioma cells that were treated with toxic concentrations of Zn. The results showed that the cellular ATP level decreased from 2.7 pmol/cell (<10% cell death) in average control cell samples to 0.36 pmol/cell as the concentration of Zn increased to 120 mg/l (>35% cell death) in culture medium.

The chemical resolution of racemic cis-2-hydroxymethyl-5(cytosine-1 '-yl)-1,3-oxathiolane (BCH-189)-one direct method to obtain lamivudine as anti-HIV and anti-HBV agent

Racemic cis-BCH-189 can be resolved to (-)-enantiomer (lamivudine) and (+)-enantiomer by esterification of cis-2-hydroxymethyl-5-(N-4(')-acetylcytosine-1'-yl)-1,3-oxathiolane and (+)-menthyl chloroformate in CH3CN with pyridine as base. The two diastereomers of ester were seperated by recrystallization in methanol at 0degreesC. Lamivudine was obtained by deprotection of (-)-diastereomer with high yield.

Effect of rare earth element on the metabolism in rats by high resolution proton nuclear magnetic resonance spectroscopy

The high-field nuclear magnetic resonance (NMR) spectra can be used for the rapid multicomponent analysis in small amounts of biological fluids. In this paper, the effect of La (NO3)(3) on the rats' metabolism in urine was investigated by H-1 NMR analysis. The experimental groups of wistar rats were injected intraperitoneally with La(NO3)(3) at doses of 0.2, 2.0, 10 and 20mg/kg body weight. The remarkable variation of low molecular weight metabolites in urine has been identified by H-1 NMR spectra, in which dimethylamine, N, N-dimethylglycine, urea, alpha -ketoglutarate, trimethylamine N-oxide, succinate, citrate and amino acids have been suggested as NMR markers for renal damage and ethanol, lactate, taurine as the markers for liver damage. This work may assess its possible use in the early detection of biochemical changes associated with Rare Earth induced kidney and liver dysfunction.

Resolution of 3,3 '-dioxo-1,1 '(3H,3 ' H)spirobi[isobenzofuran]-5,6,5 ' 6 '-tetracarboxylic acid and Optically active Polyimides thereof

3,3'-Dioxo-1.1'(3H.3'H)spirobi[isobenzofuran]-5,6,5',6 acid 1 was resolved successfully and the corresponding optically active polyimides PI were synthesized. The properties of the optically active PI and the racemic one were investigated. The results showed that the specific rotation of(-)-PI was about two times to that of the: (+)-PI, and the regularity of the optically active PI was higher than that of the racemic one.

High resolution electron microscopy study of single chain single crystals of gutta percha

Single chain single crystals (SCSC) of gutta percha (GP) were prepared by a dilute-solution spraying method. Electron diffraction (ED) patterns revealed that the single chain single crystal was of a new crystalline modification, the delta form. The images of SCSC of GP obtained with a high resolution electron microscope (HREM) showed a two dimensional periodic structure. Most of the images consisted of lattice fringes derived from the (001) zone. This is the first time that the single chain single crystal images of GP have been observed at a molecular level. Micrographs were image processed using optical filtering methods to improve the signal-to-noise ratio, and were compared with computer-generated simulations of the images. From the viewpoint of the defects seen in high resolution images, the crystal formation and melting processes are discussed. (C) 1998 Elsevier Science Ltd. All rights reserved.

High resolution solid-state NMR and DSC study of poly(ethylene glycol) silicate hybrid materials via sol-gel process

Hybrid materials incorporating poly(ethylene glycol) (PEG) with tetraethoxysilane (TEOS) via a sol-gel process were studied for a wide range of compositions of PEG by DSC and high resolution solid-state C-13- and Si-29-NMR spectroscopy. The results indicate that the microstructure of the hybrid materials and the crystallization behavior of PEG in hybrids strongly depend on the relative content of PEG. With an increasing content of PEG, the microstructure of hybrid materials changes a lot, from intimate mixing to macrophase separation. It is found that the glass transition temperatures (T-g) (around 373 K) of PEG homogeneously embedded in a silica network are much higher than that (about 223 K) of pure PEG and also much higher in melting temperatures T-m (around 323 K) than PEG crystallites in heterogeneous hybrids. Meanwhile, the lower the PEG content, the more perfect the silica network, and the higher the T-g of PEG embedded in hybrids. An extended-chain structure of PEG was supposed to be responsible for the unusually high T-g of PEG. Homogeneous PEG-TEOS hybrids on a molecular level can be obtained provided that the PEG. content in the hybrids is less than 30% by weight. (C) 1998 John Wiley & Sons, Inc.

MICROSTRUCTURE ANALYSIS OF 3 SEGMENTED COPOLYMERS CONTAINING POLYDIMETHYLSILOXANE BY SOLID-STATE HIGH-RESOLUTION NMR

The microstructure of two bicomponent and one tricomponent segmented copolymers, based on polydimethylsiloxane, poly(p-hydroxystyrene) or/and polysulfone, were investigated using an extended Goldman-Shen pulse sequence, proton spin-spin relaxation measurements, and C-13 and Si-29 NMR spectra. The results indicate that there exist four phases with different sizes, components and morphological structure in the segmented copolymers studied in this work, i. e., a rigid-chain phase of very slow motion, a rigid-chain-rich phase of slow motion, a flexible-chain-rich phase of fast motion and a flexible-chain phase of faster motion. The sizes of different domains, calculated from the spin diffusion rates, are about 50-100 angstrom for the flexible-chain-rich phase of fast motion and 200-300 angstrom for the flexible-chain phase of faster motion. The relative quantities of polydimethylsiloxane in the flexible-chain phase of fast motion are slightly different in different kinds of segmented copolymers.

A HIGH-RESOLUTION SOLID-STATE NMR AND DSC STUDY OF MISCIBILITY AND CRYSTALLIZATION BEHAVIOR OF POLY(VINYL ALCOHOL)/POLY(N-VINYL-2-PYRROLIDONE) BLENDS

Blends of crystallizable poly(vinyl alcohol) (PVA) with poly(N-vinyl-2-pyrrolidone) (PVPy) were studied by C-13 cross-polarization/magic angle spinning (CP/MAS) n.m.r. and d.s.c. The C-13 CP/MAS spectra show that the blends were miscible on a molecular level over the whole composition range studied, and that the intramolecular hydrogen bonds of PVA were broken and intermolecular hydrogen bonds between PVA and PVPy formed when the two polymers were mixed. The results of a spin-lattice relaxation study indicate that blending of the two polymers reduced the average intermolecular distance and molecular motion of each component, even in the miscible amorphous phase, and that addition of PVPy into PVA has a definite effect on the crystallinity of PVA in the blends over the whole composition range, yet there is still detectable crystallinity even when the PVPy content is as high as 80 wt%. These results are consistent with those obtained from d.s.c. studies.

RESOLUTION OF CLOSELY SPACED LINES WITH KALMAN FILTERING IN INDUCTIVELY COUPLED PLASMA ATOMIC EMISSION-SPECTROMETRY

Effects of some factors on the performance of our Kalman filter in discrimination of closely spaced overlapping signals were investigated. The resolution power of the filter for overlapping lines can be strengthened by reduction of the step size in scans. The minimum peak separation of two lines which the Kalman filter can effectively handle generally equals two to three times the step size in scans. Significant difference between the profiles of the analysis and interfering lines and multiple lines from matrix in the spectral window of the analysis line are very helpful for the Kalman filter to discern closely spaced analysis and interfering signals correctly, which allow the filter well to resolve the line pair with very small peak distance or even the entirely coincident lines.