Chiral effects for the inhibition of acetylcholinesterase by organophosphorus pesticides were investigated for insecticide malathion and malaoxon, which is a metabolic product of malathion in living organisms. Studies were carried out using a bienzymatic biosensor with immobilized acetylcholinesterase, choline oxidase, and with Prussian Blue used as a mediator. In both cases the R enantiomers accelerate acetylocholinesterase inhibition. The chiral effect in inhibition was much more pronounced in fast flow measurements than in batch measurements. 相似文献
Spliced leader (SL) RNA trans-splicing adds a N2,N2,7-trimethylguanosine cap (TMG) and a 22-nucleotide sequence, the SL, to the 5′ end of mRNAs. Both non-trans-spliced with a monomethylguanosine cap (MMG) and trans-spliced mRNAs co-exist in trans-splicing metazoan cells. Efficient translation of TMG-capped mRNAs in nematodes requires a defined core of nucleotides within the SL sequence. Here we present a chemical procedure for the preparation and purification of 5′-terminal capped MMG and TMG wild-type, and mutant 22 nt spliced leader RNAs (GGU/ACUUAAUUACCCAAGUUUGAG) with or without a 3′ biotin tag. 相似文献
The following ions [UO2(NO3)3]−, [UO2(ClO4)3]−, [UO2(CH3COO)3]− were generated from respective salts (UO2(NO3)2, UO2(ClO4)3, UO2(CH3COO)2) by laser desorption/ionization (LDI). Collision induced dissociation of the ions has led, among others, to the
formation of UO4− ion (m/z 302). The undertaken quantum mechanical calculations showed this ion is most likely to possess square planar geometry as
suggested by MP2 results or strongly deformed geometry in between tetrahedral and square planar as indicated by DFT results.
Interestingly, geometrical parameters and analysis of electron density suggest it is an UVI compound, in which oxygen atoms bear unpaired electron and negative charge. 相似文献
The concentration of elements in sediments is an important aspect of the quality of water ecosystems. The element concentrations in bottom sediments from Goczalkowice Reservoir, Poland, were investigated to determine the levels, accumulation and distribution of elements; to understand the contamination and potential toxicity of elements; and to trace the possible source of pollution. Sediments were collected from 8 sampling points. The functional speciation, mobility and bioavailability of elements were evaluated by means of modified Tessier sequential extraction. The element contents were measured by optical emission spectrometry with inductively coupled plasma. The experimental results were analyzed using chemometric methods such as principal component analysis and cluster analysis to elucidate the metal distributions, correlations and associations. The highest concentrations of most elements were found at the center of the reservoir. The distribution of metals in the individual fractions was varied. To assess the extent of anthropogenic impact indices, contamination factor, degree of contamination, metal pollution index and risk assessment code were applied. The calculated factors showed the highest contamination factor and the ability of chromium to be released from sediments. The degree of contamination showed that the area is characterized by a very high contamination. Strontium and manganese showed high potential ecological risk for sediments. 相似文献
The methods used for the separation and analytical determination of individual isomers are based on interactions with substances exhibiting optical activity. The currently used methods for the analysis of optically active compounds are primarily high-performance separation methods, such as gas and liquid chromatography using chiral stationary phases or chiral selectors in the mobile phase, and highly efficient electromigration techniques, such as capillary electrophoresis using chiral selectors. Chemical sensors and biosensors may also be designed for the analysis of optically active compounds. 相似文献
A bicomponent mixture in the orthoconic aniferroelectric phase, based on three-ring esters with fluorine atoms and ether group in a nonchiral chain, was doped with a variety of cyano-terminated compounds containing different numbers of phenyl rings in a rigid core and a terminal chain of different chirality. Compounds with two chiral chains were added to the basic mixture. The influence of the structure and concentration of dopant on the temperature-dependence of helical parameters, such as helical pitch and twist sense, were assessed by spectrophotometric and polarimetric methods. Long cyano-terminated compounds were found to be better than the other dopants tested for improving the usable properties of the antiferroelectric mixtures. 相似文献
MRI offers high spatial resolution with excellent tissue penetration but it has limited sensitivity and the commonly administered contrast agents lack specificity. In this study, two sets of iron oxide nanoparticles (IONPs) were synthesized that were designed to selectively undergo copper‐free click conjugation upon sensing of matrix metalloproteinase (MMP) enzymes, thereby leading to a self‐assembled superparamagnetic nanocluster network with T2 signal enhancement properties. For this purpose, IONPs with bioorthogonal azide and alkyne surfaces masked by polyethylene glycol (PEG) layers tethered to CXCR4‐targeted peptide ligands were synthesized and characterized. The IONPs were tested in vitro and T2 signal enhancements of around 160 % were measured when the IONPs were incubated with cells expressing MMP2/9 and CXCR4. Simultaneous systemic administration of the bioorthogonal IONPs in tumor‐bearing mice demonstrated the signal‐enhancing ability of these ‘smart’ self‐assembling nanomaterials. 相似文献
At the crossroads : A unique carbon‐bridged annulene motif—dehydroquatyrin—is imprinted into the molecular structure of the tetraazuliporphyrin tetracation (see picture). The macrocycle, which lies at the intersection of annulene, carbocation, and porphyrin chemistry, is obtained by the standard condensation of azulene and arylaldehyde followed by oxidation. The meso positions of the tetracation are susceptible to anionic or weak nucleophilic attack.