[Synthesis of spyropyran derivatives of retinal and study of their interaction with bacterioopsin from Halobacterium salinarum].

The synthesis of retinal analogue series that contain a spyropyran moiety instead of a trimethylcyclohexene ring was proposed. The process of the retinal analogue interaction with bacterioopsin from apomembranes of Halobacterium salinarum and the spectral properties of the newly formed pigments were studied. The English version of the paper: Russian Journal of Bioorganic Chemistry, 2008, vol. 34, no. 2; see also http://www.maik.ru.

[A convenient synthesis of retinal derivatives with a modified trimethylcyclohexene ring]. / Udobnyi sposob polucheniia proizvodnykh retinalia, modifitsirovannykh po trimetiltsiklogeksenovomy kol'tsu.

A method of simultaneous one-stage synthesis of three retinal derivatives (5,6-dioxo-5,6-seco-, 5,6-dihydro-5,6-epoxy-, and 4-oxoretinal) was proposed, with the yield of the first derivative being approximately 50%. These compounds are useful tools for studying the antitumor activity of retinoids, the reconstituted bacteriorhodopsin analogues with changed parameters of photocycle, and the reactivity of retinal derivatives in the processes of oxidation by molecular oxygen. The English version of the paper: Russian Journal of Bioorganic Chemistry, 2002, vol. 28, no. 6; see also http://www.maik.ru.

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 (approximately 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 beta-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 new platelet aggregation inhibitors substituted with pyridylisoxazoles and their 4,5-dihydroanalogs]. / Sintez novykh ingibitorov agregatsii trombotsitov--zameshchennykh piridilizoksazolov i ikh 4,5-digidroanalogov.

A number of substituted pyridylisoxazoles and their 4,5-dihydro analogs were synthesized by 1,3-dipolar cycloaddition of substituted nitrile oxides to either alkenes or alkynes. The synthesized compounds inhibit arachidonic acid-induced aggregation of human thrombocytes at concentrations of 10(-6) to 10(-3) M. Due to low toxicity, these compounds can be regarded as potential antithrombosis medicines.

Supercooperativity in platelet aggregation: substituted pyridyl isoxazoles, a new class of supercooperative platelet aggregation inhibitors.

The phenomenon of supercooperativity in platelet aggregation is manifested by the occurrence of clear-cut thresholds in dose-response relationships; in such cases the Hill coefficient has unusually high values. Approximation, by the Hill equation, of the relationship of the rate of arachidonate-induced platelet aggregation to the concentrations of either the inducer or inhibitors such as substituted pyridyl isoxazoles (synthesized by us), indomethacin, and pinane thromboxane A2, demonstrated that the Hill coefficients ranged from 30 to 100. 3-(3-Pyridyl)-5-phenylisoxazole, which exhibited maximal anti-aggregatory activity among the synthesized compounds, inhibited neither cyclooxygenase nor thromboxane synthase. The compounds affected the signal transduction pathway at/or posterior to the stage of thromboxane A2 reception.