A GC-MS Chemotaxonomic Study on Lipophilic Compounds in the Bark of subsp. Trees from the Population Growing in Akademgorodok, Novosibirsk (Russia).

Determination of chemotypes and of their role in the polymorphism of populations is an important field in the research on secondary metabolites of plants. In the present study, by gas chromatography coupled with mass spectrometry, the composition of bark extracts from rowan subsp. was determined for 16 trees growing within Akademgorodok of Novosibirsk, with bark samples collected both in winter and summer.

Cationic penetrating antioxidants switch off Mn cluster of photosystem II in situ.

Mitochondria-targeted antioxidants (also known as 'Skulachev Ions' electrophoretically accumulated by mitochondria) exert anti-ageing and ROS-protecting effects well documented in animal and human cells. However, their effects on chloroplast in photosynthetic cells and corresponding mechanisms are scarcely known. For the first time, we describe a dramatic quenching effect of (10-(6-plastoquinonyl)decyl triphenylphosphonium (SkQ1) on chlorophyll fluorescence, apparently mediated by redox interaction of SkQ1 with Mn cluster in Photosystem II (PSII) of chlorophyte microalga Chlorella vulgaris and disabling the oxygen-evolving complex (OEC).

Radical ions with nearly degenerate ground state: correlation between the rate of spin-lattice relaxation and the structure of adiabatic potential energy surface.

Paramagnetic spin-lattice relaxation (SLR) in radical cations (RCs) of the cycloalkane series in liquid solution was studied and analyzed from the point of view of the correlation between the relaxation rate and the structure of the adiabatic potential energy surface (PES) of the RCs. SLR rates in the RCs formed in x-ray irradiated n-hexane solutions of the cycloalkanes studied were measured with the method of time-resolved magnetic field effect in the recombination fluorescence of spin-correlated radical ion pairs. Temperature and, for some cycloalkanes, magnetic field dependences of the relaxation rate were determined.

Intrinsic reaction parameters for electron transfer from aromatic radical anions to vicinal dibromoalkanes in alkane solutions.

In diffusion-assisted bimolecular reactions, the elementary reaction mechanism is typically difficult to study, because the kinetics of the intrinsic reaction is masked by the diffusive motion of the reactants. One of the possible experimental approaches to solve the problem is the precise determination of the effective reaction radii, R = k/(4πD(S)), where k is the stationary value of the reaction rate constant and D(S) is the sum of the diffusion coefficients of the reactants involved. In this work, this approach has been applied to study the reaction between radical anions of aromatic compounds (diphenylacetylene and diphenylsilane) and vicinal dibromoalkanes (1,2-dibromoethane and trans-1,2-dibromocyclohexane) in liquid alkanes.

Radical cations of branched alkanes as observed in irradiated solutions by the method of time-resolved magnetic field effect.

Spin dynamics in radical ion pairs formed under ionizing irradiation of n-hexane solutions of two branched alkanes 2,3-dimethylbutane and 2,2,4-trimethylpentane has been studied by the method of time-resolved magnetic field effect in recombination fluorescence. Experimental curves of the magnetic field effect are satisfactorily described by assuming that the spin dynamics is determined by the hyperfine interactions in the radical cation (RC) of branched alkane under study with hyperfine coupling (HFC) constants averaged by internal rotations of RC fragments. The HFC constants determined from the magnetic field effect curves are close to those estimated within DFT B3LYP approach.

Degenerate electron exchange reaction of n-alkane radical cations in solution.

The degenerate electron exchange (DEE) reaction involving radical cations (RCs) of n-nonane, n-dodecane, and n-hexadecane in n-hexane solution was studied over the temperature range 253-313 K using the method of time-resolved magnetic field effect in recombination fluorescence of spin-correlated radical ion pairs. In the dilute solutions the rate constant of DEE was found to be 200 times slower than the diffusion limit. Using n-nonane as an example, we showed that two reasons are responsible for the low value of the RC self-exchange rate: (1) conformational variability of molecules and RCs and (2) the activation barrier of DEE reaction.