The cyclodimerisation of 3-methyl-2-butenenitrile

3-Methyl-2-butenenitrile (1) cyclodimerised on treatment with lithium diisopropylamide in dimethoxyethane at temperatures between ?78°C and 0°C to 3-amino-4-cyano-1,5,5-trimethyl-1,3-cyclohexadiene (2) the structure of which was established by acid hydrolysis to the known 4-cyano-1,5,5-trimethyl-1-cyclohexene-3-one (3).     

Conical parametric scattering of a single extraordinary beam in BaTiO3 crystal

In this paper, the parametric scattering of a single extraordinary polarized beam of laser in BaTiO₃ photorefractive crystal has been investigated experimentally and theoretically. The resulting pattern consists of beam fanning, isotropic ring, and anisotropic one. Among all parts of scattering pattern, isotropic ring has not been studied as much as beam fanning and anisotropic ring, and there still are some differences in reports about it. Therefore, the study has mainly focused on this part. In this experimental configuration, isotropic ring is just visible in positive angles although the other parts of parametric scattering pattern can be visible from behind and in front of the crystal. In addition to steady state pattern in forward and backward directions, its transient behavior with the rotation of crystal has been studied. The results of experiments have been analyzed carefully, and their theoretical explanations have been presented based on the standard theory of parametric scattering in photorefractive crystals. It has been shown that this configuration corresponds to the so called parametric B-process scattering.     

On-chip chiral and achiral separation of amphetamine and related compounds labeled with 4-fluoro-7-nitrobenzofurazane

Amphetamine and analogous compounds have been labeled with 4-fluoro-7-nitrobenzofurazane and analyzed on a microfabricated chip. Separation of norephedrine, ephedrine, cathinone, pseudoephedrine, methcathinone, amphetamine and methamphetamine is demonstrated using micellar electrokinetic capillary chromatography (MEKC) and laser-induced fluorescence (LIF) detection. Chiral separations of individual drugs were studied using neutral and negatively charged cyclodextrins (CDs) with and without the addition of an organic modifier and/or sodium dodecyl sulfate (SDS). The best results were obtained using a highly sulfated gamma-CD (HS-gamm-CD) in combination with a low concentration of SDS. To obtain complete separation of a mixture of (+/-)-norephedrine, (+/-)ephedrine, (+/-)-pseudoephedrine, (+/-)-methcathinone, (+/-)-amphetamine and (+/-)-methamphetamine it was necessary to add a small amount (1.5 mM) of SDS to the separation buffer. Optimized chiral separation was achieved within 7 min using an S-folded separation channel, a separation voltage of 8 kV and a buffer consisting of 50 mM phosphate (pH 7.35), 10 mM HS-gamma-CD and 1.5 mM SDS.     

Imaging of peptide adsorption to microfluidic channels in a plastic compact disc using a positron emitting radionuclide

A method for studying peptide-surface interactions within microfluidic channels by radionuclide imaging is described. With the high surface area-to-volume ratio of channels in miniaturised devices, combined with low amounts of analyte, non-specific peptide adsorption is a critical issue. The objective of the study was therefore to develop a method capable of direct detection of adsorbed peptide within microfluidic channels. A micro-device consisting of channels moulded in a plastic compact disc was chosen for the study, together with two selected peptides of different lengths and isoelectric point (pI) values. A bifunctional chelator, DOTA, was attached to the peptide by conjugation and labelled with the short-lived positron emitting radionuclide 68Ga. Quantitative images of radiotracer distribution within the microfluidic channels were obtained using a PhosphorImager system. The power of the method was demonstrated by the ability to clearly measure changes in adsorption when varying a number of parameters that typically affect peptide adsorption. These included surface modifications, analyte concentration, pH, and ionic strength. Additionally, two quantification methods were developed and compared. Radionuclide imaging also permitted visualisation of adsorption and release processes in microchannel chromatographic columns. The results suggest that radionuclide imaging is a suitable tool not only for the study of peptide adsorption to the microchannels presented in this study but also as a versatile tool to measure peptide-surface interactions in a wide variety of miniaturised structures and devices.     

Self-chemical ionization of diethylzinc

The self-chemical ionization of diethylzinc is examined by Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry and semiempirical molecular orbital calculations. Electron impact of diethylzinc neutral produces the radical cation, C(4)H(15)Zn(+) (m/z x 122), which reacts further with the neutral (C(2)H(5))(2)Zn to give the following product ions: Zn(+) (m/z x 64), C(2)H(5)Zn(+) (m/z x 93), C(4)H(9)Zn(+) (m/z x 121), C(4)H(11)Zn(2)(+) (m/z x 187), and C(6)H(15)Zn(2)(+) (m/z x 215). To determine the structure and pathways for production of these ions, monoisotopic (12)C(4)H(15)(64)Zn(+), (64)Zn(+) and (12)C(2)H(5)(64)Zn(+) were individually isolated and reacted with the neutral background. We also performed semiempirical molecular orbital calculations (ZINDO/1). The molecular orbital calculations and experimental data are consistent in predicting that the ethyl group on the diethylzinc cation carries the positive charge. Copyright 1999 John Wiley & Sons, Ltd.     

怀孕期头发中一些元素含量的变化趋势

用同步辐射激发X射线荧光分析,对11个产妇怀孕期间头发内一些元素含量的变化趋势进行了测量,在各自对比的基础上,得到了一些结果。     

Indirect laser-induced fluorescence detection of explosive compounds using capillary electrochromatography and micellar electrokinetic chromatography

Mixtures of nitroaromatic and nitramine explosive compounds and their degradation products were analyzed using electrokinetically driven separations with both indirect laser-induced fluorescence (IDLIF) and UV absorption detection. Complete separations of the 14-component mixture (EPA 8330) were achieved using both capillary electrochromatography (CEC) and micellar electrokinetic chromatography (MEKC). IDLIF detection was performed using an epifluorescence system with excitation provided by a 635 nm diode laser and micromolar concentrations of the dye Cy-5 as the visualizing agent. While the sensitivity of the two detection methods was similar for the nitroaromatic compounds, the nitramines could only be detected using UV absorption due to their low fluorescence quenching efficiency of Cy-5. The detection sensitivity using IDLIF was limited by low frequency oscillations in the fluorescence background. The oscillations increased with higher electric field strength and were attributed to thermal fluctuations caused by Joule heating. Due to the more conductive running buffer and higher separation currents used in MEKC, sensitive IDLIF detection could only be achieved using low (approximately 100 V/cm) field strengths, resulting in long analysis times. CEC separations, which are typically run with low conductivity mobile phases to avoid bubble formation, are less sensitive to this effect. In CEC separations with IDLIF detection a stable fluorescence background using Cy-5 could be established using only a nonporous stationary phase. In capillaries packed with porous silica particles, anomalous migration behavior was observed with charged dye molecules and a stable fluorescence background could not be established under electrokinetic flow. This is the first demonstration of IDLIF in packed channel CEC.     

In silico targeting PAD4 for the treatment of rheumatoid arthritis

Structural Chemistry - Rheumatoid arthritis (RA) is an autoimmune disorder that causes chronic inflammation with periodic bursts of activity in multiple synovial joints which lead to irreversible...     

Nuclear orbiting and anomalies in nuclear reactions

In this paper, we report our measurements of back-angle oxygen and carbon particle yields from ¹⁶O+⁸⁹Y, ¹²C+⁹³Nb reactions forming the same compound nucleus ¹⁰⁵Ag at the same excitation energy and spin distribution. We find anomalously large oxygen yield and entrance channel dependence at high excitation energies from ¹⁶O+⁸⁹Y reaction implying formation of a dinuclear orbiting complex. Possible connection between nuclear orbiting and fast fission is also discussed.