Molecular homochirality - the uniformity of chirality in biological molecules - is a fundamental feature of life, yet its origins remain unresolved. The correspondence between the chirality of biological monomers on Earth and that observed in ancient meteorites implies a systematic selection of chirality sign in prebiotic chemistry, rather than a stochastic process. While classical theories attribute symmetry breaking to chiral autocatalysis, such self-amplifying processes are rare and have not been empirically demonstrated in the synthesis of amino acids and carbohydrates. In contrast, chiral cross-catalysis between amino acids and carbohydrates - a mechanism consistent with known chemical behavior - could similarly amplify chiral purity. However, cross-catalysis alone cannot determine the chirality sign due to its inherent symmetry, leaving the origin of the initial bias unexplained. Although weak interactions have been proposed as a potential source of this bias, their effects are theoretically negligible, raising questions about their sufficiency. Our kinetic analysis of cross-catalytic systems reveals that even an infinitesimal preference for left-handed amino acids and right-handed carbohydrates could be sufficient to establish the homochirality observed in life. This mechanism provides a plausible link between prebiotic chemistry and the homochirality of the biosphere, offering a potential resolution to this longstanding enigma.

The northward distribution limit of groundwater fauna is generally dictated by the extent of glacial ice sheets during the Pleistocene. However, some taxa can be found far above this limit, sometimes on isolated oceanic islands, implying long-term survival in subglacial subterranean refugia. Here we report a peculiar assemblage comprising two new depigmented and blind (stygomorphic) amphipods from the subarctic ancient lake El'gygytgyn (northern Far East): Palearcticarellus hyperboreus sp. nov. and Pseudocrangonyx elgygytgynicus sp. nov. Molecular phylogenetic analyses based on five markers confirm their affinity to Crangonyctidae and Pseudocrangonyctidae, respectively. Fossil-calibrated molecular dating indicates that the ages of both species predate the onset of Pleistocene glaciations by at least an order of magnitude. Although both species are clearly adapted for subterranean life and are related to groundwater taxa, they are only known from the lake waters (5-170-m depth). Despite being nested within Pseudocrangonyctidae, P. elgygytgynicus has an atypical third uropod that preserves a vestigial inner ramus, a trait characteristic to the monotypic sister family Crymostygidae. Given that this character was the main distinguishing feature between the two families, we propose merging Crymostygidae with Pseudocrangonyctidae. Our findings represent the world's northernmost record of stygomorphic amphipods, emphasising their relictual biogeography and the importance of Lake El'gygytgyn as a long-term, high latitude refugium for ancient pre-glacial fauna. ZooBank: urn:lsid:zoobank.org:pub:3A51D1F8-E65D-4A3A-B663-D5C40272E68B.

El’gygytgyn is the only ancient lake in the Arctic that avoided continental-scale glaciations. This lake is located on an arid mountain plateau, far from the main routes of post-glacial freshwater fish dispersal, and it is therefore challenging to consider the local fauna in a historical context. Here we present a study of the ecology and evolutionary history of the local charr complex (genus Salvelinus). We found that the endemic charrs exhibit extreme longevity, contrasting lifestyles and phenotypes. Salvelinus svetovidovi is a relic benthivorous species. The remaining charrs are descendants of Salvelinus taranetzi. Mitochondrial and microsatellite DNA polymorphisms analyzed in them and in charrs from surrounding basins indicate that S. taranetzi invaded the lake from Arctic Chukotka in the late Pleistocene as two distinct, previously diverged lineages. Descendants of both lineages occupied the pelagic food chain. The first lineage has flourished as a monomorphic planktivorous population since colonization. The second represents an example of a recent in-lake adaptive divergence, in which a deepwater piscivore specialist formed a new epilimnetic ecomorph of an impressive size (up to 9.0 kg). We suggest that this diversification was triggered by modern warming in the Arctic, which led to the formation of a productive littoral ecosystem.

Abstract Cold alkaline treatment of cellulose is usually used for wood cellulose enrichment with high-molecular-weight fractions, as they are not soluble even in strong alkali solutions. The processes of the dissolution of hemicelluloses are tightly related to the processes of cellulose structure partial disassembling. Considering recent results on the nature and thermodynamics of the interactions between the chiral and helical molecules and the role of the spin-spin exchange interactions in them, it was very probable that the chemical reactions in the chiral polymer matrix should be magnetosensitive. Trying to verify this assumption and using cold alkaline treatment as an example, we obtained solid experimental confirmations of the magnetosensitivity of this process and found an alternative way of nanocellulose production. The magnetic field as well as other agents promoting the cellulose structure loosening forces the destruction of the polymer at the stage of the supramolecular structure reassembling after removing alkali. The latter leads to the cleavage of the cellulose fibers and nanoscale particles forming. On the other hand, formally, the fraction of the high-molecular-weight components insoluble in strong NaOH solutions decreases, and the repeating treatment with an alkali solution causes a significant loss of mass.

Phycobilisomes (PBSs) are giant water-soluble light-harvesting complexes of cyanobacteria and red algae, consisting of hundreds of phycobiliproteins precisely organized to deliver the energy of absorbed light to chlorophyll chromophores of the photosynthetic electron-transport chain. Quenching the excess of excitation energy is necessary for the photoprotection of photosynthetic apparatus. In cyanobacteria, quenching of PBS excitation is provided by the Orange Carotenoid Protein (OCP), which is activated under high light conditions. In this work, we describe parameters of anti-Stokes fluorescence of cyanobacterial PBSs in quenched and unquenched states. We compare the fluorescence readout from entire phycobilisomes and their fragments. The obtained results revealed the heterogeneity of conformations of chromophores in isolated phycobiliproteins, while such heterogeneity was not observed in the entire PBS. Under excitation by low-energy quanta, we did not detect a significant uphill energy transfer from the core to the peripheral rods of PBS, while the one from the terminal emitters to the bulk allophycocyanin chromophores is highly probable. We show that this direction of energy migration does not eliminate fluorescence quenching in the complex with OCP. Thus, long-wave excitation provides new insights into the pathways of energy conversion in the phycobilisome.

The molecules of chiral N-trifluoroacetylated alpha-aminoalcohols can self-assemble and form long and thin fiber-like supramolecular structures (strings). The strings effectively grow on the surface of the substrate and the amount of them, as well as their morphology, depend on the properties of the substrate. In particular, self-assembly was not observed on the electroconductive substrates, such as some metals (copper and aluminum) and graphite. The strings were found on the surface of titanium due to the peculiarities of the titanium oxide's properties. The strings usually emanate from some nucleation zones, where the growth was initiated and then proceeded spontaneously outside these areas. We supposed the relay-race scheme of the transfer of spin polarization, which describes the mechanics and thermodynamics of the observed self-assembly process. The scheme implies the preliminary orientation of two molecules, their mutual polarization accompanied by spin-polarization, and finally the binding of the molecules. We also suppose this mechanism can play a significant role in various self-assembly processes in living cells.

The rate of a chemical reaction can be sensitive to the isotope composition of the reactants, which provides also for the sensitivity of such “spin-sensitive” reactions to the external magnetic field. Here we demonstrate the effect of the external magnetic field on the enzymatic DNA synthesis together with the effect of the spin-bearing magnesium ions ( ^25 Mg). The rate of DNA synthesis monotonously decreased with the external magnetic field induction increasing in presence of zero-spin magnesium ions ( ^24 Mg). On the contrary, in the presence of the spin-bearing magnesium ions, the dependence of the reaction rate on the magnetic field induction was non-monotonous and possess a distinct minimum at 80–100 mT. To describe the observed effect, we suggested a chemical scheme and biophysical mechanism considering a competition between Zeeman and Fermi interactions in the external magnetic field.

The aim of this work is to show the role of research on electric fish and their role in fundamental problems’ solvation. We are trying to involve additional specialists in our studies. Methods. We have developed a setup allowing simultaneous multielectrode registration and visualization of electric fields around fish, which is a novel tool in electric fish studies. Results. The article is a review. We tried to show the history of electric fish research and the peculiarities of the Russian school of electroecology.

The balance between phenotypic plasticity and adaptive specialization in response to environmental pressures remains a hot topic in evolutionary biology. In fish, one of the strongest impact factors is the chemical pollution of habitats. In an attempt to assess the consequences of heavy pollution of fresh waters for resident fishes, we studied Kamchatkan charr, which undergo paedomorphosis in the case of isolation in streams of volcanic areas contaminated with heavy metals. Experiments were carried out on the resistance of charr to metal mixtures during normal development and in six experimental groups with therapeutically altered intensity of metabolism and the secretory activity of thyroid gland. Water from volcanically contaminated streams was found to be lethally toxic for embryos and early juveniles of unadapted charr. The success of acclimation to toxic exposure was correlated with an increase in thyroid status. In experiments, the group with significantly elevated thyroid status showed a significant decrease in mortality and attenuation of oxidative stress in solutions of heavy metals. Under natural conditions, hyperthyroidism provokes a redistribution of the charr’s organism resources from somatic growth and morphological differentiation to stress counteracting and accelerated maturation, which is necessary for the long-term survival of the population under conditions of increased risk of individual mortality. Our experiments highlight the role of thyroid hormones in the rapid response to habitat pollution and the subsequent adaptation of fish populations to chronic deterioration.

The self-assembly of small and always chiral molecules into fiber-like structures is a mysterious process, as the physics underlying such self-assembly is unclear. The energy necessary for this process exceeds the one provided by common dispersion interactions and hydrogen bonding. The recent results obtained by the scientific group of Prof. Naaman from the Weizmann Institute of Science fed light on the nature of forces providing for the self-assembly of chiral molecules and attributed these forces to spin-exchange interactions. Therefore, the self-assembly of chiral molecules should be magneto-sensitive. We found such sensitivity in solutions of trifluoroacetylated α -amino alcohols, and the process was inhibited by the magnetic field when fibers grew on the surface of the substrate. On the contrary, in bulk, the self-assembly was enhanced by the magnetic field and led to the formation of a dense gel, while no gelation was observed in the absence of the external magnetic field. The latter observations are the theme of this short report, aimed to declare the effect itself but not pretend to describe it in full.

One of the features that differentiate cancer cells is their increased proliferation rate, which creates an opportunity for general anti-tumor therapy directed against the elevated activity of replicative apparatus in tumor cells. Besides DNA synthesis, successful genome replication requires the reparation of the newly synthesized DNA. Malfunctions in reparation can cause fatal injuries in the genome and cell death. Recently we have found that the ultra-short single-stranded deoxyribose polynucleotides of random sequence (ssDNA) effectively inhibit the catalytic activity of DNA polymerase  $$\beta$$ . This effect allowed considering these substances as potential anti-tumor drugs, which was confirmed experimentally both in vitro (using cancer cell cultures) and in vivo (using cancer models in mice). According to the obtained results, ssDNA significantly suppresses cancer development and tumor growth, allowing consideration of them as novel candidates for anti-cancer drugs.

In some fish lineages, evolution has led to unique sensory adaptations that provide information which is not available to terrestrial animals. These sensory systems include, among others, electroreception, which together with the ability of fish to generate electric discharges plays a role in social communication and object location. Most studies on electric phenomena in aquatic animals are dedicated to selected groups of electric fishes that regularly generate electric signals (Mormyriformes, Gymnotiformes). There exist, however, several species (hitherto described as non-electric) which, though able to perceive electric signals, have now been found to also generate them. In this article, we introduce a tool that we have designed to investigate such electric activity. This required significant adaptations of the equipment used in fish with regular discharge generation. The necessary improvements were realized by using a multielectrode registration setup allowing simultaneous visualization and quantification of behavior and associated electric activity of fish, alone or in groups, with combined electro-video clips. Precise synchronization of locomotor and electric behaviors made it possible to determine the electrically active fish in a group, and also the location of the electrogenic structure inside the fish's body. Our simple registration procedure, together with data presentation, should attract a broad audience of scientists taking up the challenge of uncovering electric phenomena in aquatic animals currently treated as electrically inactive.

The flax ( Linum usitatissimum) is widely used as a source of linen oil and fiber. As a rule, the flax varieties serve to produce either seeds (oil), or stem fibers, as the "fiber'' varieties bring the low amount of seeds, while the "oil'' varieties have poor fibers that cannot be used in textile. The straw of the oil flax has not been applied in industry and has to be burned or degrade naturally in the field. However, it contains a low degree of polymerization cellulose, which can be used at least for varnish production. The main challenge in the industrial application of the oil flax cellulose is the necessity of separating the cellulose fibers and shive enriched in lignin. On the other hand, the low cost of the final products restricts the set of available tools. Here we describe a machine designed for oil flax straw stripping and several ways of further conversion of the obtained tow into microcrystalline or fluff-like cellulose. The supposed processes run at the temperatures below the water boiling point and at the atmospheric pressure and could be held in the plastic reactors.

The origin and reason for the homochirality of living cells go with the problem of a relatively narrow spectrum of the actual biological monomers compared to the whole theoretically possible spectrum of amino acids or carbohydrates. A limited number of bio-monomers implies some special feature differing from all other similar molecules that are not present in the living cell. Here we propose one of the candidates for such a peculiarity: the ability to form highly elongated helical supramolecular structures (strings) when precipitating from homochiral solutions. The strings’ forming can be accompanied by spontaneous splitting and/or chiral purification of the initially racemic mixture. Our previous theoretical reasoning was based mainly on the biomimetic systems, while now we describe the strings forming in homochiral amino acid solutions.

This work presents data on the relationship between the oligomeric state and catalytic activity of β-like DNA polymerases isolated from three cancer cell lines upon replacement of magnesium ions with iron. It was shown that the suppression of the catalytic activity of β-like DNA polymerases in the presence of divalent iron ions is related to enzyme oligomerization that can be responsible for the suppression of the magnetic isotope effect.

Two new nematode species of the genus Eudorylaimus Andrássy, 1959 found in Lake El’gygytgyn (Chukotka, Russia)—E. chukotkanus sp. n. and E. mylnikovi sp. n.—are described and illustrations are provided. E. chukotkanus sp. n. is close to E. similis (de Man, 1876) and E. imitatoris Gagarin, 1982. It differs from both species by a longer body and odontostyle, comparatively longer prerectum, longer spicules, more numerous precloacal supplements, and a less slender tail. E. mylnikovi sp. n. is morphologically close to E. chukotkanus sp. n., but it has a shorter body and odontostyle, a different shape of the vulva, shorter tail and spicules, and less numerous ventromedial supplements. The genus Arctidorylaimus Mulvey, Anderson, 1979 has lost its status as an independent taxon and is reduced to a synonym for the genus Eudorylaimus Andrássy, 1959. The morphological diagnosis of the genus Eudorylaimus is expanded.

An Erratum to this paper has been published: https://doi.org/10.1134/S1063774521340058

Distribution of different types of atherosclerotic lesions in the arterial wall is not diffuse, but is characterized by mosaicism. The causes of such distribution remain to be established. At the early stages of atherogenesis, low-density lipoprotein (LDL) particles and immune cells penetrate into the intimal layer of the arterial wall through the endothelium. In adult humans, the luminal surface of the arterial wall is a heterogeneous monolayer of cells with varying morphology including typical endothelial cells (ECs) and multinucleated variant endothelial cells (MVECs). We hypothesized that distribution of MVECs in the endothelial monolayer can be related to the distribution pattern of early atherosclerotic lesions. We obtained en face preparations of intact adult (22–59 years old) aortic wall sections that allowed us to study the endothelial monolayer and the subendothelial layer. We compared the distribution of MVECs in the endothelial monolayer with the localization of early atherosclerotic lesions in the subendothelial layer, which were characterized by lipid accumulation and immune cell recruitment. In primary culture, MVECs demonstrated increased phagocytic activity compared to mononuclear ECs. Moreover, we have shown that unaffected aortic intima contained associates formed as a result of aggregation and/or fusion of LDL particles that are non-randomly distributed. This indicated that MVECs may be involved in the accumulation of LDL in the subendothelial layer through increased transcytosis. Interaction of LDL with subendothelial cells of human aorta in primary culture increased their adhesive properties toward circulating immune cells. Study of unaffected aortic intima revealed non-random distribution of leukocytes in the subendothelial layer and increased localization of CD45+ leukocytes in the subendothelial layer adjacent to MVECs. Together, our observations indicate that MVECs may be responsible for the distribution of atherosclerotic lesions in the arterial wall by participating in LDL internalization and immune cell recruitment.

Carotenoids are potent antioxidants with a wide range of biomedical applications. However, their delivery into human cells is challenging and relatively inefficient. While the use of natural water-soluble carotenoproteins capable to reversibly bind carotenoids and transfer them into membranes is promising, the quantitative estimation of the delivery remains unclear. In the present work, we studied echinenone (ECN) delivery by cyanobacterial carotenoprotein AnaCTDH (C-terminal domain homolog of the Orange Carotenoid Protein from Anabaena), into liposome membranes labelled with BODIPY fluorescent probe. We observed that addition of AnaCTDH-ECN to liposomes led to the significant changes in the fast-kinetic component of the fluorescence decay curve, pointing on the dipole-dipole interactions between the probe and ECN within the membrane. It may serve as an indirect evidence of ECN delivery into membrane. To study the delivery in detail, we carried out molecular dynamics modeling of the localization of ECN within the lipid bilayer and calculate its orientation factor. Next, we exploited FRET to assess concentration of ECN delivered by AnaCTDH. Finally, we used time-resolved fluorescence anisotropy to assess changes in microviscosity of liposomal membranes. Incorporation of liposomes with β-carotene increased membrane microviscosity while the effect of astaxanthin and its mono- and diester forms was less pronounced. At temperatures below 30 °C addition of AnaCTDH-ECN increased membrane microviscosity in a concentration-dependent manner, supporting the protein-mediated carotenoid delivery mechanism. Combining all data, we propose FRET-based analysis and assessment of membrane microviscosity as potent approaches to characterize the efficiency of carotenoids delivery into membranes.

Our analysis of the X-ray crystal structure of canthaxanthin (CAN) showed that its ketolated β-ionone rings can adopt two energetically equal, but structurally distinct puckers. Quantum chemistry calculations revealed that the potential energy surface of the β-ionone ring rotation over the plane of the conjugated π-system in carotenoids depends on the pucker state of the β-ring. Considering different pucker states and β-ionone ring rotation, we found six separate local minima on the potential energy surface defining the geometry of the keto-β-ionone ring—two cis and one trans orientation for each of two pucker states. We observed a small difference in energy and no difference in relative orientation for the cis -minima, but a pronounced difference for the position of trans -minimum in alternative pucker configurations. An energetic advantage of β-ionone ring rotation from a specific pucker type can reach up to 8 kJ/mol ( 669cm^-1 ). In addition, we performed the simulation of linear absorption of CAN in hexane and in a unit cell of the CAN crystal. The electronic energies of S_0→S_2 transition were estimated both for the CAN monomer and in the CAN crystal. The difference between them reached 690cm^-1 , which roughly corresponds to the energy gap between A and B pucker states predicted by theoretical estimations. Finally, we have discussed the importance of such effects for biological systems whose local environment determines conformational mobility, and optical/functional characteristics of carotenoid.