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33.
Wang Y Zhang W Dong Y Fan R Sheng G Fu J 《Analytical and bioanalytical chemistry》2005,383(5):804-809
A high-performance liquid chromatographic method with fluorescence detection has been developed to determine the urinary polycyclic
aromatic hydrocarbon metabolites 2-hydroxynaphthalene, 2-hydroxyfluorene, 9-hydroxyphenanthrene, 1-hydroxypyrene and 3-hydroxybenz[a]pyrene.
Solid phase extraction (SPE) was used to clean up the samples, and washing with 30% methanol was found to be the best way
to remove interferences in the matrix. The method detection limits ranged from 0.044 μg/L for 1-hydroxypyrene to 1.615 μg/L
for 3-hydroxybenz[a]pyrene, and the recoveries ranged between 40% for 3-hydroxybenz[a]pyrene and 99% for 2-hydroxynaphthalene.
The within-day relative standard deviation was lowest for 2-hydroxynaphthalene at 0.67% and went up to 2.42% for 3-hydroxybenz[a]pyrene,
and the between-day relative standard deviation ranged from 3.84% for 9-hydroxyphenanthrene to 10.42% for 2-hydroxyfluorene.
The correlation coefficients were between 0.9962 and 0.9998. The developed method was successfully used to analyze samples
from student volunteers in a high school. 相似文献
34.
Yulian Volovenko Tatyana Volovnenko Kirill Popov 《Journal of heterocyclic chemistry》2007,44(6):1413-1419
A synthesis of N‐alkyl‐4‐chloro‐1H‐benzo[c][1,2]thiazine‐3‐carbaldehyde‐2,2‐dioxides is described. Reactivity of new β‐chloroaldehydes is investigated, a number of novel benzo[c][1,2]thiazine derivatives are synthesized and characterized using 1H, 13C‐NMR, MS and elemental analysis. 相似文献
35.
Yulian An 《Journal of Mathematical Analysis and Applications》2006,322(2):1071-1082
In this article, we consider uniqueness of positive radial solutions to the elliptic system Δu+a(|x|)f(u,v)=0, Δv+b(|x|)g(u,v)=0, subject to the Dirichlet boundary condition on the open unit ball in RN (N?2). Our uniqueness results applies to, for instance, f(u,v)=uqvp, g(u,v)=upvq, p,q>0, p+q<1 or more general cases. 相似文献
36.
针对机载武器发射产生的废气对发动机工作参数的影响,自行研制了微压差压力传感器来测
量发动机压气机后压力的突降信号,及时打开防喘系统来防止发动机喘振或停车. 论述了传
感器的结构、工作原理和设计思路以及主要组件参数的设计方法,并得出符合设计要求的试
验结果. 相似文献
37.
Development of a direct ELISA based on carboxy-terminal of penicillin-binding protein BlaR for the detection of β-lactam antibiotics in foods 总被引:1,自引:0,他引:1
Juan Peng Guyue Cheng Lingli Huang Yulian Wang Haihong Hao Dapeng Peng Zhenli Liu Zonghui Yuan 《Analytical and bioanalytical chemistry》2013,405(27):8925-8933
β-Lactam antibiotics, including penicillins and cephalosporins, are commonly used in veterinary medicine. Illegal use and abuse of β-lactams could cause allergy and selected bacterial resistance. BlaR-CTD, the carboxy-terminal of penicillin-recognizing protein BlaR from Bacillus licheniformis ATCC 14580, was utilized in this study to develop a receptor-based ELISA for detection and determination of β-lactam antibiotics in milk, beef, and chicken. This assay was based on directly competitive inhibition of binding of horseradish peroxidase-labeled ampicillin to the immobilized BlaR-CTD by β-lactams. The assay was developed as screening test with the option as semiquantitative assay, when the identity of a single type of residual β-lactam was known. The IC50 values of 15 β-lactam antibiotics, including benzylpenicillin, ampicillin, amoxicillin, dicloxacillin, oxacillin, nafcillin, cefapirin, cefoperazone, cefalotin, cefazolin, cefquinome, ceftriaxone, cefotaxime, cefalexin, ceftiofur and its metabolite desfuroylceftiofur were evaluated and ranged from 0.18 to 170.81 μg L?1. Simple sample extraction method was carried out with only phosphate-buffered saline, and the recoveries of selected β-lactam antibiotics in milk, beef, and chicken were in the range of 53.27 to 128.29 %, most ranging from 60 to 120 %. The inter-assay variability was below 30 %. Limits of detection in milk, beef, and chicken muscles with cefquinome matrix calibration were 2.10, 30.68, and 31.13 μg kg?1, respectively. This study firstly established a rapid, simple, and accurate method for simultaneous detection of 15 β-lactams in edible tissues, among which 11 β-lactams controlled by European Union could be detected below maximum residue limits. Figure
The receptor-based ELISA for blank sample (negative samples, left) and sample containing β-lactam antibiotics (positive samples, right) 相似文献
38.
Hao M Li Y Wang Y Yan Y Zhang S Li G Yang L 《Journal of chemical information and modeling》2011,51(10):2560-2572
An unusually large data set of 397 piperazinyl-glutamate-pyridines/pyrimidines as potent orally bioavailable P2Y(12) antagonists for inhibition of platelet aggregation was studied for the first time based on the combination of three-dimensional quantitative structure-activity relationship (3D-QSAR), molecular docking, and molecular dynamics (MD) methods. The comparative molecular field analysis (CoMFA) and comparative molecular similarity index analysis (CoMSIA) studies have been performed with a training set of 317 compounds, estimating three superimposition methods. The best CoMFA and CoMSIA models, derived from superimposition I, shows leave-one-out cross-validation correlation coefficients (Q(2)) of 0.571 and 0.592 as well as the conventional correlation coefficients (R(2)(ncv)) of 0.814 and 0.834, respectively. In addition, the satisfactory results, based on the bootstrapping analysis and 10-fold cross-validation, further indicate the highly statistical significance of the optimal models. The external predictive abilities of these models were evaluated using a prediction set of 80 compounds, producing the predicted correlation coefficients (R(2)(pred)) of 0.664 and 0.668, respectively. The key amino acid residues were identified by molecular docking, and the stability and rationality of the derived molecular conformations were also validated by MD simulation. The good concordance between the docking results and CoMFA/CoMSIA contour maps provides helpful clues about the rational modification of molecules in order to design more potent P2Y(12) antagonists. We hope the developed models could provide some instructions for further synthesis of highly potent P2Y(12) antagonists. 相似文献
39.
Zubatyuk RI Volovenko YM Shishkin OV Gorb L Leszczynski J 《The Journal of organic chemistry》2007,72(3):725-735
The contribution of aromaticity and intramolecular hydrogen bonding to relative stability, for a set of (1H-azahetero-2-ylidene)-acetaldehyde and 2-azahetero-2-yl-ethanol tautomeric pairs, has been investigated by means of quantum chemical DFT and ab initio methods up to the MP4(SDTQ)/AUG-cc-pVDZ and MP2/AUG-cc-pVTZ levels of theory. It is found that the relative energy of the tautomers is governed by the change in the degree of heterocycle aromaticity upon intramolecular hydrogen transfer. An analysis of geometrical parameters of a hydrogen-bonded system reveals a clear relationship between the aromaticity of the heterocycle, the conjugation in a resonant spacer, and the strengths of the intramolecular hydrogen bonds. This allows the conclusion to be drawn that intramolecular N-H...O and O-H...N hydrogen bonds formed are found to be resonance-assisted and their strength is dependent on the pi-donating/accepting properties of the heterocycle. On the basis of the results of the calculations, a simple model describing the mechanism of resonance assistance of hydrogen bonding has been suggested. 相似文献
40.
Aberrant DNA methylation originated from changes in DNA methyltransferase activity can lead to many genetic diseases and tumor types, and the monitoring of methyltransferase activity is thus of great importance in disease diagnosis and drug screening. In this work, by combing hybridization chain reaction (HCR) and metal ion-dependent DNAzyme recycling, we have developed a convenient enzyme-free signal amplification strategy for highly sensitive detection of DNA adenine methyltransferase (Dam MTase) activity and its inhibitors. The Dam MTase-induced methylation and subsequent cleavage of the methylated hairpin DNA probes by DpnI endonuclease lead to the release of ssDNA triggers for HCR formation of many Mg2+-dependent DNAzymes, in which the fluorescently quenched substrate sequences are catalytically and cyclically cleaved by Mg2+ to generate remarkably amplified fluorescent signals for highly sensitive detection of Dam MTase at 7.23 × 10−4 U/mL. In addition, the inhibition of different drugs to Dam MTase activity can also be evaluated with the developed method. With the advantages of simplicity and significant signal amplification over other common methods, the demonstrated biosensing approach thus offers great potential for highly sensitive detection of various methyltransferases and provides a convenient platform for drug screening for therapeutic applications. 相似文献