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91.
N. A. Borisevich S. A. Bagnich T. F. Raichenok V. N. Knyukshto A. V. Baranovskii V. N. Zhabinskii 《Journal of Applied Spectroscopy》2008,75(2):187-191
Biologically active brassinosteroid 24-epicastasterone, ring B of which contains a C=O group and has the nπ*-configuration
for a low-lying electronic excited state, exhibits rapid fluorescence. The wavelengths of the fluorescence maxima of the steroid
dissolved in hexane and acetonitrile are equal to 332 and 394 nm, respectively. The fluorescence lifetime of the steroid dissolved
in acetonitrile is τ = 9.9 nsec. Solutions of 24-epibrassinolide do not luminesce. The long-wavelength electronic absorption
band λmaxabs = 340 nm in the absorption spectrum of an ethanol solution of model compound 2, ring D of which contains a C=O group π*-conjugated with the C=C double bond of ring C, like in the spectrum of the steroid,
has a low extinction coefficient. An ethanol solution of 2 does not fluoresce. 24-Epicastasterone at 77 K in ethanol solution exhibits phosphorescence with λmaxphos = 447 nm. The phosphorescence decay is exponential with τ = 0.79 msec. Compound 2 also phosphoresces. The phosphorescence spectrum of its ethanol solution has a maximum at 490 nm. The phosphorescence decay
is nonexponential in the early stage. The phosphorescence lifetime is 25 msec in the exponential decay region.
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Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 2, pp. 182–186, March–April, 2008. 相似文献
92.
N. A. Borisevich T. F. Raichenok V. A. Khripach V. N. Zhabinskii G. V. Ivanova 《Journal of Applied Spectroscopy》2008,75(1):75-79
Electronic absorption spectra of 24-epicastasterone and 24-epibrassinolide solutions have been recorded and analyzed. The
long-wavelength band in solution spectra of the former steroid with maxima in the region 292–286 nm is assigned to the electronic
nπ*-transition of a carbonyl chromophore. The latter steroid contains an O-C=O group, for which the extinction coefficient
in this spectral region is approximately one order of magnitude less. These differences can be used to identify the studied
steroids. A method to synthesize the conjugate of 24-epicastasterone with a fluorescent label, dansylhydrazine, which shows
intense fluorescence and absorption, is described. Absorption spectra of the label and conjugate in diethylether, tetrahydrofuran,
ethanol, and acetonitrile solutions are practically independent of the solvent properties. The exceptions are solutions of
the conjugate in hexane and water. All investigated solutions of label and conjugate show intense fluorescence. As the dielectric
constant of the solvent increases, the fluorescence spectra shift to long-wavelength. The fluorescence energetic and time
characteristics of both the label and conjugate are similar, which enables the conjugate to be used in developing a method
for immunofluorescent analysis of the brassinosteroid 24-epicastasterone.
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Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 1, pp. 74–78, January–February, 2008. 相似文献
93.
N. K. Tatarskaya M. A. Zhurav S. M. Smirnov I. A. Degterev V. F. Tarasov Yu. E. Borisevich G. E. Zaikov 《Russian Chemical Bulletin》1989,38(4):722-726
1. | The decomposition of khinifur in aqueous solutions proceeds according to two parallel paths: direct photodecomposition from the first singlet activated state (monomolecular path) and reaction of the molecule in the triplet state with a molecule in the initial state (bimolecular path). |
2. | The first path does not depend on the pressure of oxygen in the solution, while the second path is inhibited by oxygen. |
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98.
A. A. Akhrem N. A. Borisevich O. V. Gulyakevich A. L. Mikhal'chuk T. F. Raichyonok S. A. Tikhomirov G. B. Tolstorozhev 《Journal of fluorescence》1999,9(4):357-361
The specific fluorescence properties as well as picosecond transient absorption features have been studied for two 8-azasteroids. It is shown that at various excitation wavelengths the essentially different final excited electronic states are realized. Because of the multicenter character of 8-azasteroids the spectroscopic data obtained may be analyzed on a basis of the mesomeric tautomerism model taking into account the dynamic combination of cis- and trans-configurations. The dependence of fluorescence spectral characteristics on the solvent nature is a manifestation of intermolecular H-bond interactions. 相似文献
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