O. V. Demina

Synthesis and properties of bacteriorhodopsin analogs containing electron-density labels in the chromophore moiety.

A method for synthesis of retinal analogs labeled with electron-density groups is suggested. The interaction of these polyene compounds with bacterioopsin in apomembrane of Halobacterium salinarum was tested. A retinal analog containing a crown-ether receptor group is able to interact readily with bacterioopsin giving rise to rapid formation of a pigment with absorption maximum at 460 nm. This pigment is capable of undergoing cyclic photoconversion. The crown-bacteriorhodopsin photocycle is extremely slow and its quantum efficiency is very low (∼3% of that in native bacteriorhodopsin). This photocycle includes an M-like intermediate with a differential absorption maximum at 380 nm. A retinal analog in which the β-ionone ring is replaced by ferrocene moiety forms a stable chromoprotein with the main absorption band at 483 nm and a shoulder near 590-610 nm.

Synthesis of spiropyran analogues of retinal and study of their interaction with bacterioopsin from Halobacterium salinarum

The synthesis of a series of retinal analogues containing the spiropyran moiety instead of trimethylcyclohexene ring was proposed. The interaction of the resulting retinal analogues with bacterioopsin from apomembranes of Halobacterium salinarum and the spectral characteristics of the new pigments were studied.

Photochromic and Cation-Binding Properties of New Crowned Spiropyrans

ABSTRACT Spectral properties of new crowned spiropyrans and their cationic complexes are described.

Bacteriorhodopsin Analogs, Bearing Modified Chromophore as a Basis for the Photochromic Materials

Abstract Relationships of the chromophore structure and photochemical behaviour of bacteriorhodopsin analogs in solution and their possible technical applications were discussed.

5-Substituted pyridylisoxazoles as effective inhibitors of platelet aggregation

A series of 5-substituted 3-pyridylisoxazoles were synthesized using [3+2] cycloaddition of nitrile oxides to alkynes with variation of substituents at position 5 of the isoxazole ring without additional synthetic stages and with retention of 2-pyridyl-, 3-pyridyl, and 4-pyridyl substituents at position 3 of the isoxazole ring. Substituted pyridylisoxazoles are the potential antiaggregatory agents showing in vitro activity in the concentration range from 1•10−6 mol L−1 to 1•10−4 mol L−1 toward the human platelet rich blood plasma with arachidonic acid being used as the inductor of aggregation. These compounds do not act as cyclooxygenase or thromboxane synthase inhibitors, nor as thrombin inhibitors.

Lake and Sea Populations of Mysis relicta (Crustacea,Mysida) with Different Visual-Pigment Absorbance Spectra Use the Same A1 Chromophore

Glacial-relict species of the genus Mysis (opossum shrimps) inhabiting both fresh-water lakes and brackish sea waters in northern Europe show a consistent lake/sea dichotomy in eye spectral sensitivity. The absorbance peak (λmax) recorded by microspectrophotometry in isolated rhabdoms is invariably 20–30 nm red-shifted in “lake” compared with “sea” populations. The dichotomy holds across species, major opsin lineages and light environments. Chromophore exchange from A1 to A2 (retinal → 3,4-didehydroretinal) is a well-known mechanism for red-shifting visual pigments depending on environmental conditions or stages of life history, present not only in fishes and amphibians, but in some crustaceans as well. We tested the hypothesis that the lake/sea dichotomy in Mysis is due to the use of different chromophores, focussing on two populations of M. relicta from, respectively, a Finnish lake and the Baltic Sea. They are genetically very similar, having been separated for less than 10 kyr, and their rhabdoms show a typical lake/sea difference in λmax (554 nm vs. 529 nm). Gene sequencing has revealed no differences translating into amino acid substitutions in the transmembrane parts of their opsins. We determined the chromophore identity (A1 or A2) in the eyes of these two populations by HPLC, using as standards pure chromophores A1 and A2 as well as extracts from bovine (A1) and goldfish (A2) retinas. We found that the visual-pigment chromophore in both populations is A1 exclusively. Thus the spectral difference between these two populations of M. relicta is not due to the use of different chromophores. We argue that this conclusion is likely to hold for all populations of M. relicta as well as its European sibling species.

New hybrid photochromic materials with switchable fluorescence

A method for synthesizing a photochromic ligand and using it as a structural element in a new nanodimensional hybrid construction in which CdSe quantum dots are covalently bonded to a spiropyran molecule has been proposed. Such a hybrid construction makes it possible to reversibly control the system fluorescence using a change in spiropyran ligand structure induced by light with different wavelengths (a reversible conversion from a colorless closed form into a colored merocyanine form). The possibilities for using this type of hybrid material for photocontrollable devices in nanophotonics are discussed.

Synthesis and study of the photochromic behavior of 3-[6′-nitro-1,3,3-trimethylspiro(indolino-2,2′-[2H]-chromen-5-yl)]propenoic acid and its ethyl ester

A new photochromic probe containing a spacer with the reactive carboxyl terminal group at the C5 atom of the photochrome molecule was synthesized. The spectral and kinetic study of the behavior of the new photochromic probes in toluene and ethanol was performed.

Synthesis and studies of photochromic properties of spirobenzopyran carboxy derivatives and their model compounds as potential markers

A number of photochromic markers, viz., spirobenzopyrans containing one or two active carboxy groups attached directly or through a spacer, as well as their model derivatives, were synthesized. The obtained compounds were characterized by instrumental methods of analysis. Spectrokinetic methods were used to study the behavior of the spirobenzopyran markers and the model derivatives in solutions in EtOH and toluene.

Modelling of prebiotic synthesis and selection of peptides under isothermal conditions and thermal cycling mode

The model peptide synthesis from mixtures of amino acids was carried out under the thermal cycling and isothermal modes. The compositions of the obtained mixtures of products and the primary amino acid sequence of the synthesized peptides were determined by Fourier transform ion cyclotron resonance mass spectrometry and tandem mass spectrometry in combination with high-performance liquid chromatography with the application of de novo sequencing of the synthesized products. The processes of abiogenous synthesis of peptides were shown to occur under relatively mild temperature conditions and give a substantially less number of peptides as compared with the possible statistical set. The evolution of the system takes place in the process of the synthesis in solid phase with the disappearance of a series of the most unstable peptides. The selection process with the formation of complementary peptides takes place in peptide synthesis under the thermal cyclic mode.