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391.
Marcela Seifrtová Jana Aufartová Jitka Vytlačilová Angelina Pena Petr Solich Lucie Nováková 《Journal of separation science》2010,33(14):2094-2108
A new ultra HPLC (UHPLC) method using both MS and fluorescence detection (FD) was developed for the determination of five fluoroquinolones in wastewaters. Systematic method development approach was compared with a conventional one. During the systematic approach, a possibility of automatic switching among four independent analytical columns of different chemistries has been used. Acidic as well as basic pH using ACN and methanol as organic modifiers was tested. The best separation of fluoroquinolones was obtained on phenyl analytical column at pH 10.5, which is a completely novel approach for separation of fluoroquinolones. Further, a new SPE procedure was developed for the sample preparation using basic pH as well. The sensitivity and selectivity of FD and MS detection were compared. FD at basic pH 10.5 demonstrated lower sensitivity than at acidic pH, which is conventionally performed. At basic pH, UHPLC‐MS/MS was found about two orders of magnitude more sensitive than FD. Both methods were validated and subsequently UHPLC‐FD method was used for the evaluation of stability of fluoroquinolones. UHPLC‐MS/MS method was used for the analysis of wastewater samples. Norfloxacin and ciprofloxacin were detected in samples of influent and effluent from wastewater treatment plant. Ofloxacin was detected only in influent from wastewater treatment plant. 相似文献
392.
Rodolfo Moreno‐Fuquen Jahyr Theodoro Javier Ellena Angela Marcela Montao‐A. Reynaldo Atencio 《Acta Crystallographica. Section C, Structural Chemistry》2010,66(8):o425-o428
The title 2:1 complex of 3‐nitrophenol (MNP) and 4,4′‐bipyridyl N,N′‐dioxide (DPNO), 2C6H5NO3·C10H8N2O2 or 2MNP·DPNO, crystallizes as a centrosymmetric three‐component adduct with a dihedral angle of 59.40 (8)° between the planes of the benzene rings of MNP and DPNO (the DPNO moiety lies across a crystallographic inversion centre located at the mid‐point of the C—C bond linking its aromatic rings). The complex owes its formation to O—H...O hydrogen bonds [O...O = 2.605 (3) Å]. Molecules are linked by intermolecular C—H...O and C—H...N interactions forming R21(6) and R22(10) rings, and R66(34) and R44(26) macro‐rings, all of which are aligned along the [01] direction, and R22(10) and R21(7) rings aligned along the [010] direction. The combination of chains of rings along the [01] and [010] directions generates the three‐dimensional structure. A total of 27 systems containing the DNPO molecule and forming molecular complexes of an organic nature were analysed and compared with the structural characteristics of the dioxide reported here. The N—O distance [1.325 (2) Å] depends not only on the interactions involving the O atom at the N—O group, but also on the structural ordering and additional three‐dimensional interactions in the crystal structure. A density functional theory (DFT) optimized structure at the B3LYP/6‐311G(d,p) level is compared with the molecular structure in the solid state. 相似文献
393.
Few of the elements present in nature play a metabolic role in living organisms. According to their abundance, these elements are classified as macro-, micro- or trace elements, representing 93%, 5% and around 1% respectively, of the total body weight. The remaining percentage could be attributed to those elements with unknown biological functions, to others which are present only because of the exposure to polluted environment or to those intentionally introduced into the body for a special treatment. This review summarizes and discusses the most recent publications related to the on-line processing of biological samples for trace element determination using atomic spectrometry-based detectors. Preconcentration/separation procedures based on solid phase or cloud point extractions, electrochemical deposition, microdialysis, as well as chemical vapor generation are the common practice for improving the sensitivity and selectivity of the available atomic spectrometric techniques. The advantages of using isotope dilution mass spectrometry in speciation studies are also emphasized. Digestion or leaching in oxidizing acidic mixtures aided by heat or by ultrasound or microwave radiation, performed off- or on-line, is necessary to previous steps when processing solid biological samples. The most relevant analytical figures of merit such as detection limits, enrichment factors and sample throughput as well as some aspects related to the on-line system configurations and accuracy assessments are critically presented. 相似文献
394.
Marcela Janatová Jana Poltierová Vejpravová Martin Divi? 《Journal of magnetism and magnetic materials》2010,322(9-12):1140-1142
We report on magnetic properties of RCr2Si2 compounds with R=Tb, Er. The polycrystalline samples were characterized by powder X-ray diffraction and found to be isostructurally crystallizing in the ThCr2Si2-type tetragonal structure. The samples were further investigated by specific heat, AC-susceptibility and magnetization methods in the temperature range 2–900 K and in magnetic fields up to 9 T. The magnetic measurements revealed the magnetic ordering of the rare-earth moments below about 2 K, whilst no high-temperature ordering of the Cr moments was observed. The evidence of for Cr magnetism is corroborated by results of first-principles calculations based on the density functional theory (DFT). 相似文献
395.
396.
Erika Dutkov María Jesús Sayagus Martin Fabin Matej Bal Jaroslav Kov
Jaroslav Kov
Junior Martin Stahorský Marcela Achimovi
ov Zdenka Luk
ov Bujkov 《Molecules (Basel, Switzerland)》2023,28(1)
Copper, antimony and sulfur in elemental form were applied for one-pot solid-state mechanochemical synthesis of skinnerite (Cu3SbS3) in a laboratory mill and an industrial mill. This synthesis was completed after 30 min of milling in the laboratory mill and 120 min in the industrial mill, as corroborated by X-ray diffraction. XRD analysis confirmed the presence of pure monoclinic skinnerite prepared in the laboratory mill and around 76% monoclinic skinnerite, with the secondary phases famatinite (Cu3SbS4; 15%), and tetrahedrite (Cu11.4Sb4S13; 8%), synthesized in the industrial mill. The nanocrystals were agglomerated into micrometer-sized grains in both cases. Both samples were nanocrystalline, as was confirmed with HRTEM. The optical band gap of the Cu3SbS3 prepared in the laboratory mill was determined to be 1.7 eV with UV–Vis spectroscopy. Photocurrent responses verified with I–V measurements under dark and light illumination and Cu3SbS3 nanocrystals showed ~45% enhancement of the photoresponsive current at a forward voltage of 0.6 V. The optical and optoelectrical properties of the skinnerite (Cu3SbS3) prepared via laboratory milling are interesting for photovoltaic applications. 相似文献
397.
Jose Luis Ropero-Vega Joshua Felipe Redondo-Ortega Yuli Juliana Galvis-Curubo Paola Rondn-Villarreal Johanna Marcela Flrez-Castillo 《Molecules (Basel, Switzerland)》2021,26(9)
Currently, the detection of pathogens such as Escherichia coli through instrumental alternatives with fast response and excellent sensitivity and selectivity are being studied. Biosensors are systems consisting of nanomaterials and biomolecules that exhibit remarkable properties such as simplicity, portable, affordable, user‑friendly, and deliverable to end‑users. For this, in this work we report for the first time, to our knowledge, the bioinformatic design of a new peptide based on TIR protein, a receptor of Intimin membrane protein which is characteristic of E. coli. This peptide (named PEPTIR‑1.0) was used as recognition element in a biosensor based on AuNPs‑modified screen‑printed electrodes for the detection of E. coli. The morphological and electrochemical characteristics of the biosensor obtained were studied. Results show that the biosensor can detect the bacteria with limits of detection and quantification of 2 and 6 CFU/mL, respectively. Moreover, the selectivity of the system is statistically significant towards the detection of the pathogen in the presence of other microorganisms such as P. aeruginosa and S. aureus. This makes this new PEPTIR‑1.0 based biosensor can be used in the rapid, sensitive, and selective detection of E. coli in aqueous matrices. 相似文献
398.
Florea Dumitrascu Ana-Maria Udrea Mino R. Caira Diana Camelia Nuta Carmen Limban Mariana Carmen Chifiriuc Marcela Popa Coralia Bleotu Anamaria Hanganu Denisa Dumitrescu Speranta Avram 《Molecules (Basel, Switzerland)》2022,27(9)
The efficient regioselective bromination and iodination of the nonsteroidal anti-inflammatory drug (NSAID) carprofen were achieved by using bromine and iodine monochloride in glacial acetic acid. The novel halogenated carprofen derivatives were functionalized at the carboxylic group by esterification. The regioselectivity of the halogenation reaction was evidenced by NMR spectroscopy and confirmed by X-ray analysis. The compounds were screened for their in vitro antibacterial activity against planktonic cells and also for their anti-biofilm effect, using Gram-positive bacteria (Staphylococcus aureus ATCC 29213, Enterococcus faecalis ATCC 29212) and Gram-negative bacteria (Escherichia coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853). The cytotoxic activity of the novel compounds was tested against HeLa cells. The pharmacokinetic and pharmacodynamic profiles of carprofen derivatives, as well as their toxicity, were established by in silico analyses. 相似文献
399.
Jose Luis Ropero-Vega Joshua Felipe Redondo-Ortega Juliana Paola Rodríguez-Caicedo Paola Rondn-Villarreal Johanna Marcela Flrez-Castillo 《Molecules (Basel, Switzerland)》2022,27(9)
The detection of pathogens through alternative methodologies based on electrochemical biosensors is being studied. These devices exhibit remarkable properties, such as simplicity, specificity, and high sensitivity in monitoring pathogens. However, it is necessary to continue conducting studies that adequately improve these characteristics, especially the recognition molecule. This work aims to design and evaluate a new peptide, named PEPTIR-2.0, as a recognition molecule in electrochemical biosensors to detect E. coli O157:H7 in water. PEPTIR-2.0 was obtained from modifications of the PEPTIR-1.0 peptide sequence, which was previously reported and exhibited excellent properties for detecting and quantifying this pathogenic microorganism. PEPTIR-1.0 is a peptide analogous to the TIR (Translocated Intimin Receptor) protein capable of interacting with the Intimin outer membrane. The basis of this study was to obtain, by using bioinformatics tools, a molecule analogous to PEPTIR-1.0 that maintains its three-dimensional structure but increases the hydrophobic interactions between it and Intimin, since these intermolecular forces are the predominant ones. The designed PEPTIR-2.0 peptide was immobilized on screen-printed electrodes modified with gold nanoparticles. The detection capacity of E. coli O157:H7 in water was evaluated using electrochemical impedance spectroscopy in the presence of other microorganisms, such as P. aeruginosa, S. aureus, and non-pathogenic E. coli. The results showed that PEPTIR-2.0 confers remarkable specificity to the biosensor towards detecting E. coli, even higher than PEPTIR-1.0. 相似文献
400.
Implementation of the diagonalization‐free algorithm in the self‐consistent field procedure within the four‐component relativistic scheme 下载免费PDF全文
Marcela Hrdá Tomáš Kulich Michal Repiský Jozef Noga Olga L. Malkina Vladimir G. Malkin 《Journal of computational chemistry》2014,35(23):1725-1737
A recently developed Thouless‐expansion‐based diagonalization‐free approach for improving the efficiency of self‐consistent field (SCF) methods (Noga and ?imunek, J. Chem. Theory Comput. 2010, 6, 2706) has been adapted to the four‐component relativistic scheme and implemented within the program package ReSpect. In addition to the implementation, the method has been thoroughly analyzed, particularly with respect to cases for which it is difficult or computationally expensive to find a good initial guess. Based on this analysis, several modifications of the original algorithm, refining its stability and efficiency, are proposed. To demonstrate the robustness and efficiency of the improved algorithm, we present the results of four‐component diagonalization‐free SCF calculations on several heavy‐metal complexes, the largest of which contains more than 80 atoms (about 6000 4‐spinor basis functions). The diagonalization‐free procedure is about twice as fast as the corresponding diagonalization. © 2014 Wiley Periodicals, Inc. 相似文献