Polarization selectivity of interaction of DNA molecules with X-ray radiation

The optimum form of a long helical molecule, which DNA is, has been calculated in terms of the classical electromagnetic theory. Three different methods of classical electrodynamics are used: the theory of dipole radiation of electromagnetic waves, the energetic power approach, and a helical model of molecules of chiral medium. In all three cases, an identical result for the optimum geometrical form of a long spiral molecule has been obtained. The lead angle between the tangent to the helix and the plane normal to the axis of the helix should be equal to 24.5 degrees. This condition imposes restrictions on the radius and the pitch of the helical molecule. The experimentally measured geometrical characteristics of the DNA molecule satisfy the theoretically calculated condition precisely enough. Having the optimum geometrical form, the DNA molecule is not influenced by a circularly right-polarized electromagnetic wave in the soft X-ray range λ = 7–8 nm. This wave, for which the right-handed DNA molecule is “transparent,” should propagate orthogonally to the helix axis and form a right-handed screw in space. The wave radiated by the right-handed DNA molecule orthogonally to helix axis in the range of λ ≈ 7–8 nm has, accordingly, the left-handed circular polarization. The polarization selectivity of the DNA molecule by the action of X-ray radiation is exhibited strongly enough in the wavelength range of λ ≈ 1–35 nm. The results obtained are valid for any distribution of electric currents in DNA, i.e., for any sequence of nitrogenous bases in DNA.     

High-Performance Tunable Multichannel Absorbers Coupled with Graphene-Based Grating and Dual-Tamm Plasmonic Structures

Plasmonics - We present a hybrid Tamm system targeting the tunable multichannel absorber. The proposed optical absorber is analyzed and investigated by using the transfer matrix method (TMM). The...     

To compete or not to compete: an experimental study of interactions between plant species with contrasting root behaviour

Game-theoretic models predict that plants with root systems that avoid belowground competition will be displaced by plants that overproduce roots in substrate shared with competitors. Despite this, both types of root response to neighbours have been documented. We used two co-occurring clonal species (Glechoma hederacea and Fragaria vesca) with contrasting root responses to neighbours (avoidance of competition and contesting of resources, respectively) to examine whether functional variation in other traits affected the success of each rooting strategy, leading to a different outcome from that predicted on the basis of root behaviour alone. Vegetative propagation rates, morphology and biomass allocation patterns were examined when each species was challenged with competition from physically separate ramets with either the same rooting strategy (intraclonal competition) or the contrasting rooting strategy (interspecific competition). Contrary to the predictions of game-theoretic models, the species that exhibits avoidance of root competition (Glechoma) was not competitively inferior to the species that does not (Fragaria). Glechoma achieved greater total mass in the interspecific treatment than in the intraclonal treatment. However, Fragaria did not experience more intense competition from Glechoma than it did in the intraclonal treatment. Strong interference between the two species appeared to be avoided because Glechoma invested preferentially in rapid exploitation of unoccupied space, whereas Fragaria invested in increasing the competitive ability and local persistence of established ramets. Our results suggest that interspecific trade-offs between traits related to competitive ability and resource exploitation can allow coexistence of species with contrasting rooting behaviours. Full assessment of the adaptive value of different root responses to neighbours therefore requires concurrent consideration of the combined effects of a wide array of functional traits.     

The role of leaf lobation in elongation responses to shade in the rosette-forming forb Serratula tinctoria (Asteraceae)

BACKGROUND AND AIMS: Lobed leaves are considered selectively advantageous in conditions of high irradiance. However, most studies have involved woody species, with only a few considering the role of leaf lobation in herbaceous rosette species. In this study, it is hypothesized that, in addition to its adaptive value in high light, leaf lobation may add to the function of petioles as vertical spacers in herbaceous species in conditions of strong competition for light. METHODS: To test this hypothesis, leaf development was examined under seasonally changing natural light conditions and a field experiment was conducted in which light climate was manipulated in a wooded meadow population of Serratula tinctoria. KEY RESULTS: No changes in leaf lobation were observed in response to experimental shading or different natural light conditions. However, in tall herbaceous vegetation, plants with highly lobed leaves achieved significantly greater vertical elongation than plants with less-lobed leaves. In contrast to herbaceous shade, tree shade had no effect on leaf elongation, suggesting differential responsiveness to competition from neighbouring herbs versus overhead shade. In shading treatments, imposed shade could only be responded to by the elongation of leaves that were produced late in development. CONCLUSIONS: The results show that extensive leaf lobation can enable greater leaf elongation in response to shade from surrounding herbaceous vegetation. The different morphological responses displayed by Serratula tinctoria to different types of shade demonstrate the importance of critically assessing experimental designs when investigating phenotypic plasticity in response to shade.     

Information given by interneuronal junctions of the rat cerebral cortex during the post-asphyxia period

Using PTA technique, the organization of subsynaptic units (paramembrane specialized formations of the cytoskeleton) was revealed in the molecular layer of the rat neocortex during post-asphyxia period. The density and summarized length of the active contact zone (ACZ) with different degree of maturity of subsynaptic units were calculated and the information was evaluated. It was revealed that the total length of ACZ synapses was restored to the control level on the 7th day after asphyxia and the information of the synaptic pool was 30.1% on the 14th day, in spite of a significant deficiency in the synapse density. The information of the synaptic pool was restored mainly due to hypertrophy of interneuronal contacts with well developed presynaptic grating.     

Synaptic structure of human cerebral cortex in chronic hypoxia and epileptic changes in the brain

Comparative quantitative analysis of the synaptic pool of the neuropil in the molecular layer at the temporal epilepsy and cerebral chronic hypoxia (brain tumor, that is not accompanied with a convulsive syndrome) has been performed using biopsy material. As a control the brain of practically healthy persons, who died a sudden death, has been used. The contrasting method of the phosphoric tungsten acid alcohol solution and OsO4 has been applied. An essential complication in the cerebral cortex synaptic structure in the zone with a regular epileptic activity, as well as preservation of quantitative density of synapses near to the control level at epilepsy have been revealed. At the chronic hypoxia simplification in organization of interneuronal connections at the level of synapses and reduction in the quantitative density of synapses have been noted. The complication of the cerebral cortex synaptic structure and epileptic changes++ of the brain is considered as an increase in the neuropil informativity, contributing to keeping a long-term memory about the character of epileptic manifestations.     

Synthesis of nucleoside 5'-fluoroalkylphosphonate--compounds with potential antiviral properties]

Several 5'-fluoroalkylphosphonates of 3'-azido-3'-deoxythymidine and 3'-deoxy-2',3'-didehydrothymidine were synthesized as potential antiviral compounds. Fluoromethyl, difluoromethyl, fluorochloromethyl and vinyl phosphonates were used as phosphonylating components, with dicyclohexylcarbodiimide or triisopropylbenzenesulphonyl chloride as condensing reagents.