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Ratiometric fluorescent probes based on 3-hydroxyflavone (3HF) are highly sensitive tools for studying polarity, hydration, electronic polarizability, and electrostatics in different microheterogeneous systems, including protein molecules. In the present work, a reactive derivative of 3HF, 6-bromomethyl-4'-diethylamino-3-hydroxyflavone, recently synthesized in our group, was applied to label covalently bovine lens alpha-crystallin. The labeling of SH and NH(2) groups are clearly distinguished by spectroscopic criteria. We observe that the NH(2) labeling creates the positive charge in the proximity to fluorophore, which results in strong internal Stark effect producing the shift in excitation spectrum by ca. 15 nm. Analysis of excitation-dependent fluorescence spectra allows separation of the emission profiles of these SH- and NH(2)-labeled species. Applying recently developed multiparametric analysis of the obtained emission spectra, we described the physicochemical properties of the sites of SH and NH(2) labeling in alpha-crystallin. The site of SH labeling has medium-low polarity (dielectric constant, epsilon = 4.9 +/- 0.9) is protic, and does not contain proximal aromatic residues (according to the obtained refractive index, n = 1.41 +/- 0.14). The site of NH(2) labeling is also of medium-low polarity. The novel label due to its two-wavelength ratiometric response and high sensitivity to the type of labeling may offer new possibilities in the studies of structure, dynamics, and interactions of proteins by probing their SH- and NH(2)-labeling sites. 相似文献
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A. N. Mazeika A. M. Popov V. I. Kalinin S. A. Avilov A. S. Sil’chenko E. Ya. Kostetsky 《Biophysics》2008,53(5):409-416
The ability of holothurian triterpene glycosides (cucumarioside A2-2 from Cucumaria japonica, cucumarioside G1 from C. fraudatrix, frondoside A from C. frondosa, and holotoxin A1 from Apostichopus japonicus) to form supramolecular lipid-saponin complexes was studied. TEM demonstrated that all the studied compounds form supramolecular cholesterol-saponin complexes (nanoparticles) in aqueous medium. The complexes formed by cucumarioside A2-2, holotoxin A1, and frondoside A had a tubular structure and fundamentally differed in the structure from the particles produced by cucumarioside G1. The morphology of the nanoparticles formed by cucumarioside A2-2, holotoxin A1, and cucumarioside G1 changed depending on the fraction of cholesterol in the lipid-saponin system; however, this pattern was not observed for frondoside A. At the same molar fraction of cholesterol in the lipid-saponin system, cucumarioside A2-2 formed the particles with the most pronounced tubular structure; the cholesterol-saponin complexes of holotoxin A1 had a less pronounced tubular structure, whereas the structure of frondoside A particles was extremely heterogeneous. Comparative analysis of the morphology of the described supramolecular complexes and specific structural features of the glycosides demonstrated that the structure of the corresponding nanoparticles depended on the degree of branching of the carbohydrate moiety in the glycoside molecule and the complexation with cholesterol was determined by the specific features of aglycone structure. Thus, the feasibility of producing new generation antigen carriers using the complexes in question was proved. 相似文献
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Sea Cucumbers Triterpene Glycosides, the Recent Progress in Structural Elucidation and Chemotaxonomy
Vladimir I. Kalinin Alexandra S. Silchenko Sergey A. Avilov Valentin A. Stonik Alexey V. Smirnov 《Phytochemistry Reviews》2005,4(2-3):221-236
Triterpene glycosides are characteristic metabolites of sea cucumbers (Holothurioidea, Echinodermata). Majority of the glycosides
belong to holostane type (lanostane derivatives with 18(20)-lactone). Carbohydrate chains of these glycosides contain xylose,
glucose, quinovose, 3-O-methylglucose and 3-O-methyl sylose. During the last 5 years, main investigations were focused on holothurians belonging to the order Dendrochirotida
collected in the North Pacific, North Atlantic, Antarctic and in subtropical waters. The glycosides of holothurians belonging
to the order Aspidochirotida have also been studied. The most uncommon structural features of carbohydrate chains of new glycosides
were: (1) the presence of quinovose as fifth terminal monosaccharide unit and the presence of two quinovose residues; (2)
the presence of glucose instead of common xylose as fifth terminal monosaccharide unit; (3) trisaccharide carbohydrate chain;
(4) the presence of two 3-O-methylxylose terminal monosaccharide units; (5) the presence of sulfate group at C-3 of quinovose residue. New glycosides
without lactone or with 18(16)-lactone and having shortened side chains have also been isolated. The presence of 17α and 12α-hydroxyls,
which are characteristic for glycosides from holothurians belonging to the family Holothuriidae (Aspidochirotida) in glycosides
of dendrochirotids confirms parallel and relatively independent character of evolution of glycosides. All three families belonging
to the order Aspidochirotida: Holothuriidae, Stichopodidae and Synallactidae have similar and parallel trends in evolution
of the glycosides carbohydrate chains, namely from non-sulfated hexaosides to sulfated tetraosides. Sets of aglycones in glycosides
from holothurians belonging to the genus Cucumaria (Cucumariidae, Dendrochirotida) are specific for each species. The carbohydrate chains are similar in all representatives
of the genus Cucumaria. 相似文献
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This paper estimates CO2 emission and net ecosystem exchange (NEE) between the atmosphere and the surface of bog in the south taiga of the European part of Russia for the summer periods of 2013–2015. Flux measurements are carried out by the static chamber method every 7–10 days in three experimental sites with homogenous conditions of soil moisture and vegetation type. Statistically significant differences in CO2 fluxes and NEE are found between different experimental sites. It is shown that an assessment of the significance of bogs in CO2 balance with the atmosphere must be made with consideration for the spatial heterogeneity of bogs. 相似文献
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Kovalchuk SN Kozhemyako VB Atopkina LN Silchenko AS Avilov SA Kalinin VI Rasskazov VA Aminin DL 《The Journal of steroid biochemistry and molecular biology》2006,101(4-5):226-231
Estrogenic potency of six triterpene glycosides, Holothurin A, Holotoxin A1, Frondoside A, Cucumarioside A2-2 and Cauloside C, that are natural products and semi-synthesized Ginsenoside-Rh2, were examined with yeast two-hybrid system, including expressed genes of human estrogen receptor, hER, the co-activator TIF2 and lacZ as a reporter gene. Only Ginsenoside-Rh2 exhibited significant moderate estrogenic activity in the concentration range of 10−7 to 10−6 M. Its effect was approximately 30% of the activity of 17β-estradiol applied at half-effective concentration. This indicates Ginsenosides-Rh2 is a weak phytoestrogen. The sea cucumber triterpene glycosides, Holothurin A, Holotoxin A1, Cucumarioside A2-2 and Frondoside A, and plant glycoside Cauloside C had no appreciable estrogenic activity. Data obtained by yeast two-hybrid assay reflect structure–activity relationship between tested compounds and 17β-estradiol. Only Ginsenoside-Rh2 has some similarity in chemical structure with 17β-estradiol that might explain affinity of this glycoside to the hER receptor. 相似文献
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Moisy D Avilov SV Jacob Y Laoide BM Ge X Baudin F Naffakh N Jestin JL 《Journal of virology》2012,86(17):9122-9133
Influenza virus has evolved replication strategies that hijack host cell pathways. To uncover interactions between viral macromolecules and host proteins, we applied a phage display strategy. A library of human cDNA expression products displayed on filamentous phages was submitted to affinity selection for influenza viral ribonucleoproteins (vRNPs). High-mobility-group box (HMGB) proteins were found to bind to the nucleoprotein (NP) component of vRNPs. HMGB1 and HMGB2 bind directly to the purified NP in the absence of viral RNA, and the HMG box A domain is sufficient to bind the NP. We show that HMGB1 associates with the viral NP in the nuclei of infected cells, promotes viral growth, and enhances the activity of the viral polymerase. The presence of a functional HMGB1 DNA-binding site is required to enhance influenza virus replication. Glycyrrhizin, which reduces HMGB1 binding to DNA, inhibits influenza virus polymerase activity. Our data show that the HMGB1 protein can play a significant role in intranuclear replication of influenza viruses, thus extending previous findings on the bornavirus and on a number of DNA viruses. 相似文献
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