排序方式: 共有29条查询结果,搜索用时 31 毫秒
21.
Irina Bashkirtseva Lev Ryashko Tatyana Ryazanova 《The European Physical Journal B - Condensed Matter and Complex Systems》2017,90(9):161
A problem of the analysis of the noise-induced extinction in multidimensional population systems is considered. For the investigation of conditions of the extinction caused by random disturbances, a new approach based on the stochastic sensitivity function technique and confidence domains is suggested, and applied to tritrophic population model of interacting prey, predator and top predator. This approach allows us to analyze constructively the probabilistic mechanisms of the transition to the noise-induced extinction from both equilibrium and oscillatory regimes of coexistence. In this analysis, a method of principal directions for the reducing of the dimension of confidence domains is suggested. In the dispersion of random states, the principal subspace is defined by the ratio of eigenvalues of the stochastic sensitivity matrix. A detailed analysis of two scenarios of the noise-induced extinction in dependence on parameters of considered tritrophic system is carried out. 相似文献
22.
Ryazanova OA Zozulya VN Voloshin IM Karachevtsev VA Makitruk VL Stepanian SG 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2004,60(8-9):2005-2011
Absorption and fluorescent spectra as well as fluorescence polarization degree of imidazo-[4,5-d]-phenazine (F1) and its two modified derivatives, 2-trifluoridemethylimidazo-[4,5-d]-phenazine (F2) and 1,2,3-triazole-[4,5-d]-phenazine (F3), were investigated in organic solvents of various polarities and hydrogen bonding abilities. Extinction coefficients of F2 and F3 are increased, their fluorescence Stokes shifts are reduced in comparison with those for unmodified imidazophenazine. For F3 a red shift of the longwave absorption band is observed by 15-20 nm. Modifications of imidazophenazine have led to a sufficient increase of fluorescence polarization degrees that enables to use F2 and F3 as promising fluorescent probes with polarization method application. The configuration, atomic charge distribution and dipole moments of the isolated dye molecules in the ground state were calculated by the DFT method. The computation has revealed that ground state dipole moments of F1, F2, and F3 differ slightly and are equal to 3.5, 3.2, and 3.7D, respectively. The changes in dipole moments upon the optical excitation for all derivatives estimated using Lippert equation were found to be Deltamu = 9 D. The energies of the electronic S1<--S0 transition in solvents of different proton donor abilities were determined, and energetic diagram illustrating the substituent effect was plotted. For nucleoside analogs of these compounds, covalently incorporated into a nucleotide chain, we have considered a possibility to use them as fluorescent reporters of hybridization of antisense oligonucleotides, as well as molecular anchors for its stabilization. 相似文献
23.
Victor N. Zozulya Olga A. Ryazanova Igor M. Voloshin Alexandr Yu. Glamazda Victor A. Karachevtsev 《Journal of fluorescence》2010,20(3):695-702
Self-assembly of tetracationic porphyrin TMPyP4+ onto polyanionic matrix of inorganic polyphosphate (PPS) in aqueous solutions has been studied in a wide range of molar phosphate-to-dye
ratios using techniques of polarized fluorescence, absorption, resonance Raman spectroscopy and static light scattering. The
binding of TMPyP4+ to PPS is characterized by the binding constant of 3 × 105 M−1 and the cooperativity parameter of about 150. The fluorescence quenching of the bound TMPyP4+ evidences the stacking of the porphyrine chromophores. Under the stoichiometric binding ratio TMPyP4+ forms extended continuous face-to-face aggregates (so-called H-aggregates) which manifest themselves by a blue shift (12 nm)
and a large hypochromisity (51%) of the Soret absorption band. Each face-to-face TMPyP4+ stack is formed with participation of four PPS chains. Formation of such columnar aggregates is promoted by the ability of
PPS chains to take a helix conformation where negative charges are arranged along two oppositely situated rows with intercharge
distance of 0.36 nm which corresponds to the thickness of the porphyrin π-electronic system. The ability of each PPS strand
to be template for formation of two porphyrin stacks results in the integration of the adjacent stacks into higher-order aggregates
which dimension was estimated from the fluorescence polarization data. 相似文献
24.
Denis A. Komarov A. D. Ryazanova I. A. Slepneva V. V. Khramtsov I. M. Dubovskiy V. V. Glupov 《Applied magnetic resonance》2009,35(4):495-501
The main component of the insect immune system is melanotic encapsulation of pathogenic organisms. Molecular mechanisms of
destruction of an encapsulated pathogen are poorly understood. Reactive oxygen species (ROS) are considered as probable cytotoxic
agents responsible for destruction of pathogenic organisms in insect hemolymph. In the present work the formation of H2O2 during melanization in Galleria mellonella hemolymph in the presence of catalase inhibitor NaN3 was detected. Enhanced rates of H2O2 generation were observed in the hemolymph of insects activated by injection of bacterial cells. Using spin trapping technique
in combination with electron paramagnetic resonance spectroscopy we demonstrated that production of H2O2 in the hemolymph causes the formation of highly toxic reactive oxygen species, hydroxyl radical. However, neither H2O2 nor hydroxyl radical were detected in the absence of NaN3 in agreement with the high catalase activity in the hemolymph. These observations allow us to propose a unique mechanism
of pathogen-targeted cytotoxicity based on localized hydroxyl radical generation within a melanotic capsule. 相似文献
25.
Clauwaert KM Van Bocxlaer JF Major HJ Claereboudt JA Lambert WE Van den Eeckhout EM Van Peteghem CH De Leenheer AP 《Rapid communications in mass spectrometry : RCM》1999,13(14):1540-1545
This paper describes the investigation of the potential of a quadrupole orthogonal acceleration time-of-flight mass spectrometer (Q-TOF) equipped with an atmospheric pressure ionisation interface for quantitative measurements of small molecules separated by reversed phase liquid chromatography. To this end, the detection limits and linear dynamic range in particular were studied in an LC/MS/MS experiment using 3,4-methylenedioxymethamphetamine standards and 3,4-methylenedioxyethylamphetamine for internal standardisation. In a second phase, the experiment was repeated with real biological extracts (whole blood, serum, and vitreous humour). A calibration for 3,4-methylenedioxymethamphetamine and its metabolite 3,4-methylenedioxyamphetamine was prepared in each of these matrices again using 3,4-methylenedioxyethylamphetamine as internal standard. The resulting quantitative data were compared with those obtained by liquid chromatography with fluorescence detection for the same extracts. The Q-TOF results revealed excellent sensitivity and a linear dynamic range of nearly four decades (2-10 000 pg on-column, r(2) = 0.9998, 1/x weighting). Furthermore, all the calibration curves prepared in biological material were superimposable, LC/MS/MS and LC-fluorescence, and the quantitative results for actual samples compared very favourably. It was concluded that the Q-TOF achieves a linear dynamic range for quantitative LC/MS/MS work exceeding that of fluorescence detection and at much better absolute sensitivity. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
26.
D. G. Filatova L. N. Ryazanova O. A. Shiryaeva N. B. Zorov Yu. A. Karpov 《Journal of Analytical Chemistry》2004,59(3):243-245
The conditions for the formation of soluble complex gold ammines were considered for the subsequent determination of gold by atomic absorption spectrometry with a graphite atomizer. It was found that complex ammine solutions of pH 9–11 were stable at gold concentrations to 25 ± 5 g/mL in the test solution and that the ashing temperature could be increased to 1200°C. 相似文献
27.
Radbil' A. B. Zolin B. A. Radbil' B. A. Ryazanova T. V. Klimanskaya T. V. 《Russian Journal of Applied Chemistry》2001,74(11):1850-1853
Heterogeneous homophase hydration of camphene in the presence of H4SiW1
2O4
0, H3PW1
2O4
0, or HClO4 was studied as a selective procedure for production of isoborneol. 相似文献
28.
Ryazanova OA Voloshin IM Makitruk VL Zozulya VN Karachevtsev VA 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2007,66(4-5):849-859
The visible electronic absorption and fluorescence spectra as well as fluorescence polarization degrees of imidazo-[4,5-d]-phenazine (F1), 2-methylimidazo-[4,5-d]-phenazine (F2), 2-trifluoridemethylimidazo-[4,5-d]-phenazine (F3), 1,2,3-triazole-[4,5-d]-phenazine (F4) and their glycosides, imidazo-[4,5-d]-phenazine-N1-beta-D-ribofuranoside (F1rib), 1,2,3-triazole-[4,5-d]-phenazine-N1-beta-D-glucopyranoside (F4gl), were investigated in aqueous buffered solutions over the pH range of 0-12, where the spectral transformations were found to be reversible. The effects of protonation and deprotonation on spectral properties of these dyes were studied. We have determined the ranges of pH, where individual ionic species are predominant. In aqueous buffered solutions the fluorescence was found only for neutral species of F1, F1rib, F2, and F4gl dyes, whereas for the ionic forms of these dyes, as well as for F3 and F4 ones, the fluorescence has not been detected. The concentrational deprotonation pKa values were evaluated from experimental data. It was shown that donor-acceptor properties of the substituent group in the second position of the pentagonal ring substantially affect the values of the deprotonation constants and the character of protonation for chromophore. The substitution of a hydrogen atom in the NH-group by the sugar residue blocks the formation of the anionic species, and results in enhancement of the dye emission intensity. The steep emission dependence for F1 and F1rib over pH range of 0-7 with intensities ratio of IpH 7/IpH 1=60 allows us to propose them as possible indicator dyes in luminescence based pH sensors for investigation of processes accompanied by acidification, e.g. as gastric pH-sensors. A comparative analysis of the studied dyes has shown that F4gl is the most promising compound to be used as a fluorescent probe for investigation of molecular hybridization of nucleic acids. 相似文献
29.