Tautomerism and behavior of 3-hydroxy-2-phenyl-4H-chromen-4-ones (flavonols) and 3,7-dihydroxy-2,8-diphenyl-4H,6H-pyrano[3,2-g]chromene-4,6-diones (diflavonols) in basic media: spectroscopic and computational investigations.

Absorption and emission spectroscopic investigations and computational predictions have shown that neutral molecules of flavonols and diflavonols can exist in the ground and excited states in one or two tautomeric forms stabilized by intramolecular (in aprotic media) or intermolecular (with solvent molecule(s), in protic media) hydrogen bonds. Electronic excitation creates conditions for the transformation of tautomeric forms, accompanied by proton transfer, reflected in fluorescence spectra. Proton transfer is also probable in monoanions of diflavonols in protic media.

2-(4-Fluoro-phen-yl)-2H-chromen-4(3H)-one.

In the crystal structure of the title compound, C(15)H(11)FO(2), mol-ecules form inversion dimers through pairs of weak C-H⋯O hydrogen bonds. Dimers oriented in parallel, linked by C-H⋯π contacts, are arranged in columns along the b axis. The fluoro-phenyl ring and the benzene ring of the 2H-chromen-4(3H)-one unit are inclined to one another by 70.

[Trigger regime of the functioning of a synaptic channel].

It has been shown using the linear model describing the dynamics of biochemical reactions occurring in a synapse that, as periodic step-like impulses pass through a synaptic channel, it operates in the triggering regime. The transmission of an impulse through the channel is associated with the change of the stationary point of the corresponding dynamic system compared with the unexcited state of the synapse. As a result, the system periodically evolves between two stable stationary states.

[Study on synaptic transmission by the methods of critical phenomena theory with the model direct correlation function].

Critical phenomena in finite-size cylindrical geometry systems with the model direct correlation function were investigated. The pair correlation function, the order parameter correlation radius and critical temperature shift in a finite-size system were determined. The results obtained were utilized to estimate the temperature dependence of linear size of the activation zone in which ion channel conductivity changes in a correlative way.