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1.
Varnavski OP Ostrowski JC Sukhomlinova L Twieg RJ Bazan GC Goodson T 《Journal of the American Chemical Society》2002,124(8):1736-1743
Measurements of ultrafast fluorescence anisotropy decay in model branched dendritic molecules of different symmetry are reported. These molecules contain the fundamental branching center units of larger dendrimer macromolecules with either three (C(3))- or four (T(d), tetrahedral)-fold symmetry. The anisotropy for a tetrahedral system is found to decay on a subpicosecond time scale (880 fs). This decay can be qualitatively explained by F?rster-type incoherent energy migration between chromophores. Alternatively, for a nitrogen-centered trimer system, the fluorescence anisotropy decay time (35 fs) is found to be much shorter than that of the tetramers, and the decay cannot be attributed to an incoherent hopping mechanism. In this case, a coherent interchromophore energy transport mechanism should be considered. The mechanism of the ultrafast energy migration process in the branched systems is interpreted by use of a phenomenological quantum mechanical model, which examines the two extreme cases of incoherent and coherent interactions. 相似文献
2.
N. A. Bumagin L. I. Sukhomlinova A. N. Banchikov T. P. Tolstaya I. P. Beletskaya 《Russian Chemical Bulletin》1992,41(11):2130-2130
M. V. Lomonosov Moscow State University, 119899 Moscow. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 11, pp. 2685–2686, November, 1992. 相似文献
3.
Jonathan Pansieri Igor A. Iashchishyn Hussein Fakhouri Lucija Ostoji Mantas Malisauskas Greta Musteikyte Vytautas Smirnovas Matthias M. Schneider Tom Scheidt Catherine K. Xu Georg Meisl Tuomas P. J. Knowles Ehud Gazit Rodolphe Antoine Ludmilla A. Morozova-Roche 《Chemical science》2020,11(27):7031
The mechanism of amyloid co-aggregation and its nucleation process are not fully understood in spite of extensive studies. Deciphering the interactions between proinflammatory S100A9 protein and Aβ42 peptide in Alzheimer''s disease is fundamental since inflammation plays a central role in the disease onset. Here we use innovative charge detection mass spectrometry (CDMS) together with biophysical techniques to provide mechanistic insight into the co-aggregation process and differentiate amyloid complexes at a single particle level. Combination of mass and charge distributions of amyloids together with reconstruction of the differences between them and detailed microscopy reveals that co-aggregation involves templating of S100A9 fibrils on the surface of Aβ42 amyloids. Kinetic analysis further corroborates that the surfaces available for the Aβ42 secondary nucleation are diminished due to the coating by S100A9 amyloids, while the binding of S100A9 to Aβ42 fibrils is validated by a microfluidic assay. We demonstrate that synergy between CDMS, microscopy, kinetic and microfluidic analyses opens new directions in interdisciplinary research.Templating mechanism of S100A9 amyloids on Aβ fibrillar surfaces during amyloid co-aggregation process was revealed by synergy of biophysical methods including charge detection mass spectrometry, microscopy, kinetic and microfluidic analyses. 相似文献
4.
N. A. Bumagin L. I. Sukhomlinova T. P. Tolstaya A. N. Vanchikov I. P. Beletskaya 《Russian Chemical Bulletin》1990,39(11):2419-2419
Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2665–2666, November, 1990. 相似文献
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6.
Nikolai Kiselev Vera Rosenbush Ludmilla Kolokolova Kirill Antonyuk 《Journal of Quantitative Spectroscopy & Radiative Transfer》2008,109(8):1384-1391
We have found an anomalous (negative) spectral dependence of polarization for split comet 73P/Schwassmann–Wachmann 3, i.e. polarization degree in the I filter is systematically less (4%) than that in the R filter for both B and C subnuclei of the comet. Earlier we revealed a similar effect for comets 21P/Giacobini–Zinner, C/1999 S4 (LINEAR), and 9P/Tempel 1. Together with comet C/1989 X1 (Austin), for which the similar spectral dependence of polarization was also observed, these comets form a group characterized by some peculiar properties of their dust. Since atypical organic composition is a characteristic feature for all these comets, the anomalous spectral dependence of polarization may indicate specifics of origin of these comets. Really, most of these comets (but not all) originated from the Kuiper Belt. Also, most (but not all) of these comets belong to the group of comets depleted in carbon species in the gas phase, which is typical for comets formed in the giant-planet area of the solar system. On the other hand, all of the comets with negative spectral gradient of polarization have the dust dominated by large particles and most of them belong to the Jupiter family. This may indicate that anomalous spectral dependence of their polarization is a result of their evolution. To identify the reason of anomalous polarization, systematic spectropolarimetric observations of Jupiter-family comets are necessary. 相似文献
7.
T. P. Tolstaya L. I. Sukhomlinova A. N. Vanchikov N. A. Bumagin 《Chemistry of Heterocyclic Compounds》1999,35(1):106-111
10,11-Dihydrodibenz[b,f]iodepinium tetrafluoroborate gave only 1-(2-azidophenyl)-2-(2-iodophenylethane with the N3
– in aqueous DMSO, while with NO2
– it gave 1-(2-nitrophenyl)-2-(2-iodophenyl)ethane (93%), 9,10-dihydrophenanthrene (5%), and traces of phenanthrene. Both in pure and aqueous DMSO this cation with the Br– ion was converted into phenanthrene (80% and 68% respectively) and 1-(2-bromophenyl)-2-(2-iodophenyl)ethane (10 and 20%), while in water it gave 9,10-dihydrophenanthrene (75%) and phenanthrene (5%). A new route for the synthesis of 1-(2-aminophenyl)-2-phenylethane starting from this tetrafluoroborate has been proposed.M. V. Lomonosov Moscow State University, Moscow 119899, Russia. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, 110–115, January, 1999. 相似文献
8.
CuAl2F2(Si2O7) has been prepared by hydrothermal synthesis and its crystal structure was determined by single crystal X‐ray diffraction: space group Pnma, a = 8.8697(9), b = 14.084(2), c = 4.7553(5) Å, wR2 = 0.056, R = 0.022. Cu2+ shows elongated square pyramidal coordination. Edge‐ and corner‐sharing [AlO4F2] octahedra with fluorine atoms in cis position form layers parallel to the ac plane. Along b these layers are linked by Si2O7 groups to form a three‐dimensional framework [Al2F2(Si2O7]2–. In addition, the [CuO5] pyramides connect two Al octahedra of neighbouring layers. The crystal structure is discussed as a derivative from topaz structure. The modular (or polysomatic) approach is used for this purpose, and for modelling hypothetical related compounds. 相似文献
9.
A Muñoz ME McConney T Kosa P Luchette L Sukhomlinova TJ White TJ Bunning B Taheri 《Optics letters》2012,37(14):2904-2906
Despite numerous efforts, continuous wave (CW) lasing in dye doped, one-dimensional (1D) photonic bandgap cholesteric liquid crystal (CLC) structures has not been previously reported, to our knowledge. Here we report on the observation of lasing in such structures under both coherent (laser) and incoherent (LED) CW light excitation. To achieve this effect, we used a 1D-photonic bandgap structure made of a polymer stabilized CLC with a pitch gradient across the cell thickness. A spectral reflectivity profile of such a CLC structure reveals local minima in the area within a photonic stopband and close to it. The realization of lasing pumped by low power CW light sources opens the possibility of all-organic, compact, tunable CW lasers for display and medical applications. 相似文献
10.
Scattering by inhomogeneous particles: microwave analog experiments and comparison to effective medium theories 总被引:2,自引:0,他引:2
Ludmilla Kolokolova Bo . S. Gustafsonm 《Journal of Quantitative Spectroscopy & Radiative Transfer》2001,70(4-6):611-625
It is common practice to use effective medium theories (EMT) to estimate average, “effective” optical constants of inhomogeneous materials. A variety of EMTs were developed for different internal structures of the medium and for a variety of shapes, size distributions and physical properties of the inhomogeneities. The most popular EMTs (Maxwell Garnett, Bruggeman, Looyenga, etc.) consider inhomogeneities that are much smaller than the wavelength. The so-called extended EMTs were developed to find effective optical constants in the case of inhomogeneities comparable and slightly larger than the wavelength. This paper compares angular distribution and wavelength dependence of intensity and polarization of scattered light obtained from calculations using the most popular EMTs and extended EMTs with the results of microwave analog measurements at the microwave facilities of the University of Florida. We simulated the light scattering by organic grains with silicate inclusions of size parameter x=0.075 (≈0.01 μm), 0.60 (≈0.1 μm), and 1.24 (≈0.2 μm). The conclusion is that for inclusions of a small size and for a small volume fraction of them in the mixture all EMTs yield similar results and show reasonable agreement with experimental results. The accuracy is better for the angular dependencies of the intensity and of the polarization of the scattered light than for their wavelength dependencies. For inhomogeneities comparable and larger than the wavelength extended EMTs work better but for smaller inclusions non-extended EMTs show more accurate results. Large volume fractions of the inclusions in the mixture (>10%) essentially reduce the accuracy of the results obtained with EMTs. Based on our study we do not recommend to use EMTs in the back-scattering domain and at the scattering angles 30°<θ<70°. 相似文献