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51.
苯胺及其衍生物对斜生栅列藻的毒性研究 总被引:3,自引:0,他引:3
用生物监测的方法,研究了苯胺及其衍生物抑制斜生栅列藻生长的毒性。实验结果显示96h的EC50值苯胺衍生物的毒性比母体毒性强.这是由其脂溶性、化学活动性、极性及稳定性的大小而决定的。 相似文献
52.
A simplified method for the computation of first-, second- and higher-order derivatives of eigenvalues and eigenvectors associated with repeated eigenvalues is presented. Adjacent eigenvectors and orthonormal conditions are used to compose an algebraic equation. The algebraic equation which is developed can be used to compute derivatives of eigenvalues and eigenvectors simultaneously. Since the coefficient matrix in the proposed algebraic equation is non-singular, symmetric and based on N-space, it is numerically stable and very efficient compared to previous methods. To verify the efficiency of the proposed method, the finite element model of the cantilever beam and a mechanical system in the case of a non-proportionally damped system are considered. 相似文献
53.
As the rotation rate of magnetic recording disks increases over the next few years, lubricant spin-off from the disk surface may be significant. Lubricant thickness was measured as a function of spin time at 10000 rpm on typical carbon overcoated magnetic recording disks initially lubricated with 10–135 Å of perfluoropolyether Zdol. The viscosity of the lubricant film increased as the film thickness decreased with spin time. Lubricant spin-off in response to air shear stress on the free surface was approximately described by viscous flow. The rate of lubricant removal by evaporation was compared to the spin-off removal rate in films between 10 and 50 Å thick. Dispersion interaction and chemisorption are expected to retain a molecularly thin film of lubricant on the disk surface. 相似文献
54.
Current high performance magnetic storage devices, i.e., hard disk drives, typically operate at elevated temperatures of nominally
45–60°C. As a consequence, understanding the thermal response of the materials used in the construction of the drive becomes
imperative. In this report, we focus on the thermal behavior of a common perfluoropolyether lubricant (ZDOL) used on the carbon-overcoated,
hard disk. In particular, we show that evaporative loss of this disk lubricant, as well as bonding of the lubricant to the
carbon-overcoated disk, can occur at the temperatures encountered in the hard-disk drive. Surface energy measurements show
that the interaction of the hydroxyl-terminated perfluoropolyether ZDOL occurs principally through the end-groups. On unannealed
disks, the interaction between this “mobile” lubricant and the carbon overcoat is characterized by hydrogen bonding with the
strength of these interactions being only slightly stronger than the intermolecular hydrogen bonding characteristic of bulk
ZDOL. Upon annealing at temperatures in the range of 60–150°C, the ZDOL lubricant becomes “bonded” to the disk. The surface
energy of the bonded lubricant is substantially lower than the mobile lubricant reflecting the increased interaction strength
that occurs as a result of bonding. Since the bonded state is the lower energy state, transitions from the mobile state to
the bonded state are thermodynamically favored. The kinetics of this bonding transition, as well as the kinetics of lubricant
evaporation were studied as a function of temperature. Using a model of two competing reaction channels, the activation energies
for both lubricant bonding and lubricant evaporation were determined to be 3.6 kcal/mole and 5.4 kcal/mole respectively. Ab
initio quantum chemical modelling was used to investigate possible interaction sites on the carbon surface. Both experiment
and theory indicate that interaction of the hydroxyl-terminated ZDOL to the carbon overcoat occurs via hydrogen bonding to
oxygenated species on the carbon overcoat, with a binding energy of 5–8 kcal/mole. An esterification reaction between the
hydroxyl end-groups of ZDOL with carboxyl groups on the carbon surface as a result of annealing is shown to be consistent
with the both the surface energy data and the kinetic data.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
55.
Microwave-assisted extraction coupled to headspace solid-phase microextraction with on-fiber derivatization with gas chromatography ion trap mass spectrometry analysis is reported for the determination of aldehydes in environmental water. Hexanal, (E)-2-hexenal, heptanal, octanal, nonanal, E-2-decanal, and E, E-2,4-decadienal were employed to develop and validate this method. The effects of relevant parameters on the quantitative extraction of these analytes in this one-step procedure were systematically investigated. The aldehydes were extracted from environmental water by a poly(dimethylsiloxane)/divinylbenzene fiber using o-(2, 3, 4, 5, 6-pentafluoro)-benzylhydroxylamine as the derivatization reagent. Under microwave-assisted heating, the aldehydes were transferred from water by headspace solid phase microextraction. Thus, efficient extraction and derivatization were simultaneously achieved. The recovery values ranged from 72.2–96.9%, and the relative standard deviation was between 4.1–14% for the aldehydes. The detection limits were from 0.001–0.005 µg L?1. The method was validated illustrating its potential for the analysis of environmental water while offering simplicity and rapid analysis. 相似文献
56.
57.
Agnieszka Drd Adrianna Sawiska-Brych Dominika Kubera Magdalena Kimsa-Dudek Joanna Magdalena Gola Jolanta Adamska Celina Kruszniewska-Rajs Arkadiusz Matwijczuk Dariusz Karcz Wojciech Dbrowski Andrzej Stepulak Mariusz Gago 《International journal of molecular sciences》2022,23(23)
4-(5-methyl-1,3,4-thiadiazole-2-yl) benzene-1,3-diol (C1) and 4-[5-(naphthalen-1-ylmethyl)-1,3,4-thiadiazol-2-yl] benzene1,3-diol (NTBD) are representative derivatives of the thiadiazole group, with a high antimycotic potential and minimal toxicity against normal human fibroblast cells. The present study has proved its ability to synergize with the antifungal activity of AmB. The aim of this work was to evaluate the cytotoxic effects of C1 or NTBD, alone or in combination with AmB, on human renal proximal tubule epithelial cells (RPTECs) in vitro. Cell viability was assessed with the MTT assay. Flow cytometry and spectrofluorimetric techniques were used to assess the type of cell death and production of reactive oxygen species (ROS), respectively. The ELISA assay was performed to measure the caspase-2, -3, and -9 activity. ATR-FTIR spectroscopy was used to evaluate biomolecular changes in RPTECs induced by the tested formulas. The combinations of C1/NTBD and AmB did not exert a strong inhibitory effect on the viability/growth of kidney cells, as evidenced by the negligible changes in the apoptotic/necrotic rate and caspase activity, compared to the control cells. Both NTBD and C1 displayed stronger anti-oxidant activity when combined with AmB. The relatively low nephrotoxicity of the thiadiazole derivative combinations and the protective activity against AmB-induced oxidative stress may indicate their potential use in the therapy of fungal infections. 相似文献
58.
Nicols Núez-Navarro Javier Salazar Muoz Francisco Castillo Csar A. Ramírez-Sarmiento Ignacio Poblete-Castro Flavia C. Zacconi Loreto P. Parra 《International journal of molecular sciences》2022,23(20)
Indigoids are natural pigments obtained from plants by ancient cultures. Romans used them mainly as dyes, whereas Asian cultures applied these compounds as treatment agents for several diseases. In the modern era, the chemical industry has made it possible to identify and develop synthetic routes to obtain them from petroleum derivatives. However, these processes require high temperatures and pressures and large amounts of solvents, acids, and alkali agents. Thus, enzyme engineering and the development of bacteria as whole-cell biocatalysts emerges as a promising green alternative to avoid the use of these hazardous materials and consequently prevent toxic waste generation. In this research, we obtained two novel variants of phenylacetone monooxygenase (PAMO) by iterative saturation mutagenesis. Heterologous expression of these two enzymes, called PAMOHPCD and PAMOHPED, in E. coli was serendipitously found to produce indigoids. These interesting results encourage us to characterize the thermal stability and enzyme kinetics of these new variants and to evaluate indigo and indirubin production in a whole-cell system by HPLC. The highest yields were obtained with PAMOHPCD supplemented with L-tryptophan, producing ~3000 mg/L indigo and ~130.0 mg/L indirubin. Additionally, both enzymes could oxidize and produce several indigo derivatives from substituted indoles, with PAMOHPCD being able to produce the well-known Tyrian purple. Our results indicate that the PAMO variants described herein have potential application in the textile, pharmaceutics, and semiconductors industries, prompting the use of environmentally friendly strategies to obtain a diverse variety of indigoids. 相似文献
59.
Azza Troudi Jean Michel Bolla Naouel Klibi Jean Michel Brunel 《International journal of molecular sciences》2022,23(20)
Gram-negative bacteria were reported as a significant cause of infections in both community and nosocomial settings. Considered as one of the greatest threats to public health, the spread of bacteria drug resistance and the lack of effective alternative treatment options remains problematic. Herein, we report a promising strategy to combat Gram-negative resistant strains consisting of the combination of a macrolide antibiotic with a polyaminoisoprenyl adjuvant derivative leading to a significant decrease of antibiotic resistance. 相似文献
60.
Mixture Effects of Tryptophan Intestinal Microbial Metabolites on Aryl Hydrocarbon Receptor Activity
Aneta Vrzalov Petra Pe
inkov Peter Ills Soa Gursk Petr Dubk Martin Szotkowski Marin Hajdúch Sridhar Mani Zdenk Dvok 《International journal of molecular sciences》2022,23(18)
Aryl hydrocarbon receptor (AHR) plays pivotal roles in intestinal physiology and pathophysiology. Intestinal AHR is activated by numerous dietary, endogenous, and microbial ligands. Whereas the effects of individual compounds on AHR are mostly known, the effects of real physiological mixtures occurring in the intestine have not been studied. Using reporter gene assays and RT-PCR, we evaluated the combinatorial effects (3520 combinations) of 11 microbial catabolites of tryptophan (MICTs) on AHR. We robustly (n = 30) determined the potencies and relative efficacies of single MICTs. Synergistic effects of MICT binary mixtures were observed between low- or medium-efficacy agonists, in particular for combinations of indole-3-propionate and indole-3-lactate. Combinations comprising highly efficacious agonists such as indole-3-pyruvate displayed rather antagonist effects, caused by saturation of the assay response. These synergistic effects were confirmed by RT-PCR as CYP1A1 mRNA expression. We also tested mimic multicomponent and binary mixtures of MICTs, prepared based on the metabolomic analyses of human feces and colonoscopy aspirates, respectively. In this case, AHR responsiveness did not correlate with type of diet or health status, and the indole concentrations in the mixtures were determinative of gross AHR activity. Future systematic research on the synergistic activation of AHR by microbial metabolites and other ligands is needed. 相似文献