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排序方式: 共有176条查询结果,搜索用时 31 毫秒
101.
102.
Anastasia E. Kuvarina Irina A. Gavryushina Maxim A. Sykonnikov Tatiana A. Efimenko Natalia N. Markelova Elena N. Bilanenko Sofiya A. Bondarenko Lyudmila Y. Kokaeva Alla V. Timofeeva Marina V. Serebryakova Anna S. Barashkova Eugene A. Rogozhin Marina L. Georgieva Vera S. Sadykova 《Molecules (Basel, Switzerland)》2022,27(5)
Features of the biochemical adaptations of alkaliphilic fungi to exist in extreme environments could promote the production of active antibiotic compounds with the potential to control microorganisms, causing infections associated with health care. Thirty-eight alkaliphilic and alkalitolerant Emericellopsis strains (E. alkalina, E. cf. maritima, E. cf. terricola, Emericellopsis sp.) isolated from different saline soda soils and belonging to marine, terrestrial, and soda soil ecological clades were investigated for emericellipsin A (EmiA) biosynthesis, an antifungal peptaibol previously described for Emericellopsis alkalina. The analysis of the Emericellopsis sp. strains belonging to marine and terrestrial clades from chloride soils revealed another novel form with a mass of 1032.7 Da, defined by MALDI-TOF Ms/Ms spectrometers, as the EmiA lacked a hydroxyl (dEmiA). EmiA displayed strong inhibitory effects on cell proliferation and viability of HCT 116 cells in a dose- and time-dependent manners and induced apoptosis. 相似文献
103.
104.
Gawlitza K Wu C Georgieva R Wang D Ansorge-Schumacher MB von Klitzing R 《Physical chemistry chemical physics : PCCP》2012,14(27):9594-9600
The aim of the present work is the use of a water soluble enzyme in an organic solvent, still with a pronounced catalytic activity. Therefore, lipase B from Candida antarctica (CalB) is immobilized within micron-sized thermosensitive p-NIPAM hydrogel particles using a solvent exchange from polar to organic solvents. The absorbed amount of CalB is investigated at different immobilization temperatures. Confocal laser scanning microscopy (CLSM) shows that CalB is homogeneously distributed within the polymer network. An enhanced specific activity of CalB in n-hexane is achieved after immobilization within the p-NIPAM microgels. In order to get information on the supply of the substrate depending on the temperature, the activity is determined at different reaction temperatures. Additionally, the system is stable in the organic solvent, namely n-hexane, and shows a good reusability. 相似文献
105.
V. N. Emel’yanenko S. P. Verevkin C. Schick E. N. Stepurko G. N. Roganov M. K. Georgieva 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2010,84(9):1491-1497
The enthalpies of combustion and formation of S-lactic acid at 298.15 K, Δc
H
mo(cr.) = −1337.9 ± 0.8 and Δf
H
mo(cr.) = −700.1 ± 0.9 kJ/mol, were determined by calorimetry. The temperature dependence of acid vapor pressure was studied
by the transpiration method, and the enthalpy of its vaporization was obtained, Δvap
H
o(298.15 K) = 69.1 ± 1.0 kJ/mol. The temperature and enthalpy of fusion, T
m (330.4 K) and Δm
H
o(298.15 K) = 14.7 ± 0.2 kJ/mol, were determined by differential scanning calorimetry. The enthalpy of formation of the acid
in the gas phase was obtained. Ab initio methods were used to perform a conformational analysis of the acid, calculate fundamental
vibration frequencies, moments of inertia, and total and relative energies of the stablest conformers. Thermodynamic properties
were calculated in the ideal gas state over the temperature range 0–1500 K. A thermodynamic analysis of mutual transformation
processes (the formation of SS- and RS(meso)-lactides from S-lactic acid and the racemization of these lactides) and the formation
of poly-(RS)-lactide from S-lactic acid and SS- and RS(meso)-lactides was performed. 相似文献
106.
A series of possibilities are shown of increasing the sensitivity of laser microspectral analytical determinations of impurities in minerals, Steels, and aluminium alloys. When the excitation of the spectrum of the laser beam evaporated substance is transferred to a magnetic field, a considerable increase in the intensity of certain spectral lines of the basic and admixed components and a certain decrease in the intensity of the background, are observed. The intensification factor depends on the regime of the laser and the additional impulse discharge, the intensity of the magnetic field, and the utilized spectral lines. 相似文献
107.
108.
109.
Binev YI Georgieva MK Daskalova LI 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2004,60(11):2601-2610
The spectral and structural changes caused by the conversion of 2-hydroxybenzonitrile (o-cyanophenol) into the corresponding oxyanion have been followed by IR spectra, ab initio and density functional force field calculations. In agreement between theory and experiment, the conversion is accompanied by a 29 cm(-1) frequency decrease of the cyano stretching band, 2.7-fold increase in its integrated intensity, 5.8-fold (total value) intensification of the aromatic skeletal bands of Wilson's 8 and 19 types, and other essential spectral changes. According to the calculations, the strongest structural changes are the shortening of the Ph-O bond with 0.10 A, lengthenings of the adjacent CC bonds in the phenylene ring with 0.06 A and bond angle variations near the oxyanionic center. All these changes are connected with the formation of a quasi-ortho-quinonoidal structure of the o-phenylene ring in the oxyanion. According to the electronic density analysis, 0.41 e(-) (Mulliken) or 0.56 e(-) (natural bond orbital, NBO) of the anionic charge remain localized at the oxyanionic center. Conformations and hydrogen bonds have also been discussed on the basis of experimental and theoretical data. 相似文献
110.
Ivelina Georgieva Tzvetan Mihaylov Gü nther Bauer Natasha Trendafilova 《Chemical physics》2004,300(1-3):119-131
Theoretical and spectroscopic (IR and Raman) study of different 7-hydroxy-4-methylcoumarin (mendiaxon) systems (mend−, mendNa, mendCu, mendH and mendH · 2H2O) were performed at B3LYP/6-31G(d) and B3LYP/6-31++G(d,p) levels of theory. The geometric and electronic structures as well as the vibrational behavior of the systems studied were discussed: (1) as to the changes that occurred in the anion coumarin ring upon the mend−–X+ (X+ =Na+, Cu+, H+) interactions and (2) as to the changes that occurred in mendH due to hydrogen bondings in mendH · 2H2O. The largest bond length changes in the anion coumarin ring were obtained for mendH and the smallest ones for mendNa. The bond length changes were mainly produced from the electrostatic effect of the positive charge of X. The induced polarization of the C=O bond upon the mend−–X+ interactions was found to be opposite to the basic one and it led to shorter C=O bond lengths (higher ν(C=O) frequencies) in the order: mendNa, mendCu and mendH. Conversely, upon the hydrogen bonding the induced polarization of the C=O bond was found in the same direction as the basic one and it produced elongation to the C=O bond length (lower ν(C=O) frequency). On the basis of the correlations found, the ν(C=O) positions in mendNa, mendCu, mendH and mendH · 2H2O were explained. 相似文献