共查询到20条相似文献,搜索用时 11 毫秒
1.
L. Lupan Rodica Bandula Marilena Vasilescu Cristiana Bercu 《Fresenius' Journal of Analytical Chemistry》1996,355(3-4):409-411
Conformational transformations of the tetraenic nystatin chromophore under the influence of solvents and UV irradiation have been studied by absorption, fluorescence and wide-line NMR spectroscopy. 相似文献
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Iodide salts of several N-retinylidenedialkylamines were prepared and their UV-VIS spectra recorded. Their lambda max values increased as the number of hydrogen atoms on the carbons alpha to nitrogen increased. In separate experiments, iodide salts of N-retinylidene-n-butylammonium (1) and N-retinylidene-n-butylmethylammonium (2) were prepared, and their excitation energies (delta E) were measured in selected solvents of varying dielectric constant (epsilon). Data from each compound gave a straight line which converged at epsilon = 0. On the other hand, when delta E values of the iodide and bromide of 2 were plotted vs solvent epsilon, parallel rather than convergent lines were obtained. When lambda max values of 1 and 2 were measured in a greater number of solvents, the solvents fell into four main groups. The first group, regular solvents, are rigid, have fixed dipoles, neither donate nor accept H-bonds, and the delta E of 1 and 2 decreases linearly as solvent epsilon increases. This line for 2 is taken as a standard against which other solvents are judged. A second class of solvents that are good H-bond donors like CHCl3, whose dipole moment coincides with the C-H bond axis, is located in an area below the standard line. A third group, nucleophilic solvents like tetrahydrofuran, whose dipole moment is coincident with a strongly nucleophilic oxygen atom are good H-bond acceptors and are found above the standard line. Solvents with unpredictable spectroscopic behavior are classed as anomalous. 相似文献
3.
Feng S Shi H 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2007,68(2):244-249
The interaction of adenosine disodium triphosphate (ATP) with acridine yellow and its analytical application have been studied. In an alkalescent medium, adenosine disodium triphosphate react with acridine yellow to form an ion-association by virtue of electrostatic attraction and hydrophobic interaction, resulting in a remarkable enhancement of resonance light scattering (RLS) intensity of acridine yellow. The maximum scattering wavelength is at 325 nm. The spectral characteristics of the ion-associates, the effective factors and the optimum conditions have been investigated. The enhanced RLS intensity is directly proportional to the concentration of ATP in the range of 0.80-20.0 microg ml(-1) with the detection limit 0.086 microg ml(-1). The method has been successfully applied to the quick determination of ATP in tablet and injection samples. The results of the present method are in agreement with those obtained by the method in the Chinese Pharmacopoeia. 相似文献
4.
IR spectra of phenyl benzoate (PB) have been studied at various temperatures. On the basis of the calculation of the frequencies and forms of the normal phenyl benzoate molecule, the complete assignment of vibrational spectra was achieved. A conformational analysis of PB was carried out using molecular mechanics calculations. It was shown that the relative orientation of the benzene rings varies with temperature and phase state.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 459–463, March, 1995. 相似文献
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A. S. Dzalmukhanova V. P. Lodygina V. V. Komratova E. R. Badamshina 《Kinetics and Catalysis》2013,54(6):656-661
The exchange reactions of phenyl-N-phenylurethane with amines varying in structure and nature have been investigated in o-dichlorobenzene. In the absence of a catalyst and proton-donating compound, the unimolecular decomposition of phenyl-N-phenylurethane into isocyanate and alcohol takes place at a noticeable rate starting at 250°C. The exchange reactions at 60–80°C proceed as a direct exchange between the urethane and the proton donor and are second-order up to high conversions, practically until the disappearance of the entire urethane. The activation energies and apparent rate constants of the exchange reactions of phenyl-N-phenylurethane with various amines have been determined. The results have been explained in terms of the dependence of kinetic parameters of the reaction on the amine nature, structure, and nucleophilicity, on the steric accessibility of the amino group, and on the molecular organization of the solution. 相似文献
6.
E. Renault M.P. Fontaine-Aupart F. Tfibel M. Gardes-Albert M. Gardes-Albert E. Bisagni 《Journal of photochemistry and photobiology. B, Biology》1997,40(3):218-227
The antitumor drug pazelliptine (PZE) binds to natural and synthetic DNA sequences at 100 mM NaCl, pH 7.0, as deduced from the absorption and fluorescence data. Scatchard plots constructed from the results obtained with poly(dG-dC)-poly(dG-dC) give binding constants of base pairs in the range (2–6) × 105 M−1. The modifications in the absorption and fluorescence spectra observed when PZE binds to various polynucleotides, namely poly(dA-dT)-poly(dA-dT), poly(dA)-poly(dT), poly(dG-dC)-poly(dG-dC) and calf thymus DNA. reveal a change in the protonation state of the drug upon binding, increasing the apparent pKa of its 9-N nitrogen atom. The PZE excited state properties serve as a sensitive probe to distinguish between homo and hetero A-T sites as well as between AT and GC sites. Fluorescence studies reveal that energy transfer occurs from polynucleotide bases to the bound PZE chromophore, a result consistent with an intercalative mode of binding of the drug to DNA. The emission is enhanced when PZE is bound to A-T base pairs ( 30% increase of φF) whereas it is quenched in the vicinity of G-C base pairs ( 90% decrease of φF). Furthermore, the fluorescence spectrum obtained with calf thymus DNA is hardly distinguishable from that obtained with poly(dG-dC)-polu(dG-dC), suggesting a binding of PZE to G-C rich regions. 相似文献
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Spectroscopic and theoretical study on the interaction between diperoxovanadate and oxazole 总被引:1,自引:0,他引:1
Zeng B Zhu X Yu X Cai S Chen Z 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,69(1):117-122
Detailed investigations were carried out to explore the interaction systems of NH(4)VO(3)/H(2)O(2)/oxazole in aqueous solution under physiological conditions by a combined use of multinuclear NMR ((1)H, (13)C, (14)N and (51)V), diffusion ordered spectroscopy (DOSY), variable temperature NMR, electrospray ionization mass spectrometry (ESI-MS), spin-lattice relaxation and density functional calculations. The results indicated the formation of a new peroxovanadate species [OV(O(2))(2)(oxazole)](-) with oxazole coordinating to vanadium through nitrogen atom. The solution structure of the new species was predicted from theoretical calculations. 相似文献
11.
The interaction of Methylene Blue (MB) with chondroitin-4-sulfate (CHS) has been investigated using spectroscopic techniques, including UV-Vis absorption, Rayleigh resonance scattering (RRS), and circular dichroism (CD). The addition of CHS caused a decrease in the absorbance of MB at 664 nm with a new absorption band appearing at 570 nm, enhanced RRS at 314 nm and 560 nm, and also resulted in an intense CD signal at 568 nm. The Scatchard model has been applied to calculating the binding constant and the number of binding sites. The calculated parameters are consistent with the experimental results. The factors affecting the interaction were investigated. Quantitative spectroscopic methods were developed for the first time. They are based on the fact that a decrease in the absorption at 664 nm and an enhancement of the RRS intensity at 314 nm are proportional to the concentration of CHS added in a certain range. Satisfactory results were obtained on the determination of synthetic samples. 相似文献
12.
O. V. Agashkin S. V. Bogatkov K. Praliev T. D. Sokolova B. V. Unkovskii 《Chemistry of Heterocyclic Compounds》1971,7(8):1014-1018
The IR and UV spectra of stereoisomeric piperidines and decahydroquinolines were studied, and it was shown that the spectral characteristics (intensity of the long-wavelength Bohlman band of the C-H vibrations, the oscillator strength for the long-wavelength electron transition, etc.) depend on the orientation of the substituents attached to the 2- and 4-ring atoms. The problem of the capacity of the capacity of the p electrons of nitrogen for partial delocalization owing to the interaction with the anticoplanar -C-H bonds is discussed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1081–1086, August, 1971 相似文献
13.
Kelly M ElkinsDonald J Nelson 《Coordination chemistry reviews》2002,228(2):205-225
Aluminum ion (Al3+) in the ‘free’ (aquo) state is becoming increasingly prevalent in environmental waters, especially fresh waters, as a consequence of acid rain and other environmental processes. As Al3+ ion is known to affect markedly a wide range of biological systems, and since the presence of Al3+ in humans has been linked to a number of human diseases, it is important to understand the speciation of Al3+ ion in natural waters. Since some of the most important complexation agents for Al3+ in both fresh and sea waters are members of the complex humic substances group, it is important to understand the manner in which Al3+ interacts with this class of molecules, especially since binding of Al3+ to these molecules can effectively increase the bioavailability of this toxic metal ion to biological systems. The objective of this review is to present the current state of our understanding of aqueous aluminum complexation with the most acidic members (and therefore the most likely candidates for serving as Al3+ complexing agents) of the humic substances group, the fulvic acids. Much of the current knowledge has been revealed by comprehensive fluorescence titration analyses. Some additional information has come from other experimental approaches, including infrared spectroscopy, nuclear magnetic resonance spectroscopy, and a variety of electrochemical approaches. In this review, we also report on the results of our recent fluorescence and IR spectroscopy survey of the interaction of metals from of all three Nieboer and Richardson categories of environmental metals (Class A, Class B and Intermediate Class) with the fulvic acid sub-group of the humic substances. This has proven helpful in understanding some of the unique spectral behaviors of the Al3+-fulvic acid complex vis-a-vis fulvic acid complexes with many other metal ions. The results of our fluorescence and IR experiments with the model compounds, such as salicylic and phthalic acids, have allowed confirmation of the important roles played by both salicylic acid-like sites and phthalic acid-like sites in the unique complexation of Al3+ to humic substances, and help to explain some of the observed spectroscopic changes associated with Al3+ ion complexation to humic material. From the current work, it seems clear that major sources of the deviation in spectral properties between Al3+ and many other metal ions (across all three Nieboer and Richardson categories) are the unusually high value of its charge density and relatively low propensity for involvement in covalent bonding interactions (i.e. a very high ionic index combined with a relatively low covalent index in the Nieboer and Richardson classification of environmental metals), as well as affinity for certain functional groups. 相似文献
14.
Jun Wang Lijun Liu Bin Liu Ying Guo Yuanyuan Zhang Rui Xu Shixian Wang Xiangdong Zhang 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2010,75(1):366-374
Sonodynamic therapy (SDT) is an attractive antitumor treatment for recent years. In this paper, sodium magnesium chlorophyllin (SMC) as a sonosensitizer combining with ultrasonic (US) irradiation to damage bovine serum albumin (BSA) has been investigated by fluorescence and UV–vis spectroscopy. The interaction of BSA with SMC was studied by the quenching of intrinsic fluorescence at varying temperature. The quenching constants (KSV), effective binding constants (KA), apparent association constants (Ka) and binding site numbers were determined. The results indicated the quenching mechanism is a static procedure. Thermodynamic parameters show that the interactions involve hydrogen bonds, hydrophobic interactions, electrostatic interactions and complexations. The binding distance is 3.533 nm. The synergistic effect of SMC and ultrasound was estimated including the study of damage conditions. Synchronous fluorescence spectra indicate the damage to Trp residues is more serious. This paper may offer some valuable references for using spectroscopy method to study the application of chlorophyll derivatives in antitumor treatment. 相似文献
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光谱法研究11-羟基喜树碱与牛血清白蛋白的相互作用 总被引:2,自引:0,他引:2
在生理pH条件下用荧光光谱法和紫外光谱法结合化学计量学来研究10-羟基喜树碱(10-HCPT)与牛血清白蛋白(BSA)的相互作用,结果发现,10-HCPT对BSA的内源荧光有静态猝灭作用。以华法林作为标记药物,采用三维荧光技术,分别对竞争实验过程进行扫描,进而用平行因子法(PARAFAC)处理所得三维数据,并根据蛋白质结合位上药物的置换作用确定了10-HCPT的结合位置是BSA的site I。利用同步荧光光谱,考察了10-HCPT对BSA构象的影响,10-HCPT的加入使BSA构象发生变化,BSA内部残基所处环境的疏水性下降。 相似文献
17.
The spectrophotometric method was used to determine the mechanism of chiral interactions between a known chiral selector, tert-butyl carbamoylated quinine (t-BuCQN), and N-derivative amino acids (DNB-Leu). Results obtained on binding constants, free energy of binding (DeltaG), and difference in free energy of binding (DeltaDeltaG) values seem to suggest that there are three possible types of interactions between DNB-Leu and t-BuCQN: electrostatic interaction between the carboxylate group of the DNB-Leu and the ammonium group of the t-BuCQN, the donor-acceptor charge-transfer type of interaction between the (acceptor) aromatic group of the amino acid and the (donor) aromatic group of the t-BuCQN, and the hydrogen-bonding interaction between the amide group of the DNB-Leu and the carbonyl group of t-BuCQN. The strongest interaction will be observed if all of three interactions are in operation as in the case of DNB-Leu. The electrostatic interaction seems to play the dominant role in the interactions. While the charge-transfer interaction is relatively weaker, it seems, however, to be responsible for enantiomeric selectivity, namely, the closer the electron acceptor dinitrophenyl group is to the electron donor quinoline group, the higher is the enantiomeric selectivity. Specifically, in solvent with high polarity, both donor and acceptor are solvated by solvent molecules, thereby preventing them from being close. As a consequence, the interaction will be weaker and, hence, lower enantiomeric selectivity. Solvation will be less in less polar solvent which, in turn, leads to stronger interaction and higher enantiomeric selectivity. 相似文献
18.
《Supramolecular Science》1998,5(5-6):747-749
Sodium 9,10-anthraquinone-2-sulfonate (AQS) binds to the double helical DNA with a high affinity, as deduced from the absorption and fluorescence spectral data. The results of absorption spectra, KI quenching studies, competitive binding studies, and thermal denaturation experiments suggested the intercalative binding of AQS into DNA bases. 相似文献
19.
Ling X Zhong W Huang Q Ni K 《Journal of photochemistry and photobiology. B, Biology》2008,93(3):172-176
Fluorescence spectra, absorption spectra, DNA viscosity titrations, competition experiment, and iodide quenching experiment were used to study the interaction of DNA with pazufloxacin. DNA quenches the fluorescence of pazufloxacin significantly. No red shift and isobestic points are observed in UV titration experiment. DNA viscosity and iodide quenching results suggest that pazufloxacin does not intercalate into DNA. SsDNA has a stronger quenching effect on pazufloxacin than dsDNA has. Pazufloxacin interacts with DNA in a different mode from ethidium bromide, which is a typical intercalator of DNA. All these results indicate that pazufloxacin interacts with calf thymus DNA in the mode of groove binding. The quenching constant and thermodynamic constants have also been determined. 相似文献
20.
Masafumi Watanabe Toshio Kamisuki Naotoshi Akamatsu Chiaki Hirose 《Chemical physics letters》1990,170(5-6):451-456
The transient absorption and resonance CARS (coherent anti-Stokes Raman scattering) spectra of photo-excited all-trans-1,6-diphenyl-1,3, 5-hexatriene (DPH) were studied and a hitherto unknown species was detected from the spectrum observed for an acetone solution. The excited species was generated by monophotonic excitation at 337 nm (ascertained from the dependence of the CARS intensity and that of the transient absorption on the UV power). A lifetime of ≈ 2 μs was obtained by time-resolved CARS. The new species was tentatively ascribed to a radical cation because of its anomalously long lifetime, agreement of the absorption maximum, and disagreement of CARS signals from those of DPH in the S1 and T1 states and from those of the radical anion. 相似文献