A. A. Khodonov

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.

Comparison of anti-aggregatory activities of 5-phenyl-3-(3-pyridyl)isoxazole and 5-phenyl-3-(3-pyridyl)-1,2,4-oxadiazole

Two bioisosteric analogs, 5-phenyl-3-(3-pyridyl)isoxazole and 5-phenyl-3-(3-pyridyl)-1,2,4-oxadiazole, were synthesized so as to compare their antiaggregatory activities, to determine a pharmacologically active fragment in molecules of this type, and to explore the mechanisms of action of potential antiag-gregatory compounds belonging to the class of 3,5-substituted isoxazoles. Antiaggregatory activities of these compounds were studied in vitro using three aggregation inducers, such as arachidonic acid, adenosine diphosphate, and adrenaline. It was shown that 5-phenyl-3-(3-pyridyl)-1,2,4-oxadiazole and 5-phenyl-3-(3-pyridyl)isoxazole completely suppressed platelet aggregation induced by arachidonic acid and the second wave of platelet aggregation induced by adrenaline or adenosine diphosphate. The antiaggregatory activity of substituted isoxasole was 1.1–1.5 times higher than that of substituted oxadiazole. In contrast to the isoxazole analog, 5-phenyl-3-(3-pyridyl)-1,2,4-oxadiazole in concentrations of 300–400 μM partially suppressed the first wave of aggregation induced by adenosine diphosphate. It was demonstrated that both compounds were not thrombin inhibitors in vitro at concentrations up to 250 μM. Thus, introduction of a nitrogen atom into the C4-position of the isoxazole ring changes the molecule properties. It suggests that the pharmacophoric fragment of the molecule should be the whole isoxazole or 1,2,4-oxadiazole ring but not a part of the ring as was supposed previously.

Investigation of the Spectral Properties of the Crowned Retinals and Bacteriorhodopsin Analogs

ABSTRACT The spectral properties of new crowned retinal analogs and their bacteriorhodopsin complexes are described.

Influence of metal cations on spectral characteristics of crown ether vinylogs with different terminal polar groups

Complexation of crown ether vinylogs containing different terminal polar groups with alkali and alkali-earth metal ions in solutions was studied by spectrophotometry. The hypsochromic shift of absorption band maxima in the UV-Vis absorption spectra indicates that the ligands containing the monobenzocrown ether fragments interact with metal ions. The scheme of complexation was proposed, and the stability constants of the complexes were determined. The efficiency of complexation depends on the metal cation size and the structure of the ionophoric fragment.

Synthesis and Properties of a New Dye, Containing the Crown Ether Moiety

Abstract We described two synthetic routes for preparation of new crown ether derivatives of polyenals, containing variable length of the conjugation chain.