Functional basis of electron transport within photosynthetic complex I

Photosynthesis and respiration rely upon a proton gradient to produce ATP. In photosynthesis, the Respiratory Complex I homologue, Photosynthetic Complex I (PS-CI) is proposed to couple ferredoxin oxidation and plastoquinone reduction to proton pumping across thylakoid membranes. However, little is known about the PS-CI molecular mechanism and attempts to understand its function have previously been frustrated by its large size and high lability. Here, we overcome these challenges by pushing the limits in sample size and spectroscopic sensitivity, to determine arguably the most important property of any electron transport enzyme – the reduction potentials of its cofactors, in this case the iron-sulphur clusters of PS-CI (N0, N1 and N2), and unambiguously assign them to the structure using double electron-electron resonance. We have thus determined the bioenergetics of the electron transfer relay and provide insight into the mechanism of PS-CI, laying the foundations for understanding of how this important bioenergetic complex functions.

Effect of organic compounds on cognac sensory profile

Introduction. The present research featured the effect of carbonyls, phenols, furans, fatty alcohols, ethers, and other chemical compounds on the sensory properties of cognac distillates of different ages. The research objective was to identify additional criteria of sensory evaluation by measuring the effect of various compounds on perception intensity. Study objects and methods. The study featured cognac samples of different ages. The experiment involved standard methods, including high-performance liquid and gas chromatography and a mathematical analysis based on Microsoft software. Results and discussion. The content of fatty alcohols, ethers, and carbonyl compounds that formed as a result of fermentation demonstrated little change during the aging period in oak casks. A longer extraction increased the content of phenolic and furan compounds and sugars. The content of terpene compounds decreased due to their high lability. The study revealed the effect of organic compounds on taste descriptors. The article introduces multivariate equations that calculate the dependences of the descriptor intensity on the content of organic compounds. A correlation and regression analysis revealed that phenolic compounds had a significant effect on the taste formation of cognac samples, depending on the aging time. Conclusion. Organic compounds proved to affect the taste profiles of cognac samples of different ages, as well as sensory evaluation descriptors.

Diversification through sexual selection on gustatorial courtship traits in dwarf spiders

Sexual dimorphism can evolve under sexual selection or ecological factors. Sexually dimorphic male prosomal modifications are associated with gustatorial courtship in erigonines. The modifications vary from moderate elevations to bizarre shapes. Males transfer substances from these structures to females, which affect mate acceptance and fecundity. Here, we explore lability of these traits by investigating if modified prosomata are inherently linked to secretory glands, if glands evolved prior to prosomal modifications, and the possibility of convergent evolution and cryptic differentiation, aiming at assessing the possible role of this trait complex in speciation. We reconstructed the positions of glands and the musculature in the anterior part of prosomata of 76 erigonines and three outgroups using micro-CT. We incorporated these characters into an existing morphological character matrix and reanalyzed the phylogeny. Our results support the possession of glands as the ancestral state. The manifold modifications of the prosomal shape have evolved convergently. Differences in glandular positions between species with modified/unmodified prosomata suggest high lability of these traits. Cases of gland loss suggest considerable costs of gustatorial courtship. Our findings demonstrate divergent evolutionary patterns of these traits, and a likely facilitating effect of this type of sexual selection on speciation.

Redox Potential and Crystal Chemistry of Hexanuclear Cluster Compounds

Most of TM6-cluster compounds (TM = transition metal) are soluble in polar solvents, in which the cluster units commonly remain intact, preserving the same atomic arrangement as in solids. Consequently, the redox potential is often used to characterize structural and electronic features of respective solids. Although a high lability and variety of ligands allow for tuning of redox potential and of the related spectroscopic properties in wide ranges, the mechanism of this tuning is still unclear. Crystal chemistry approach was applied for the first time to clarify this mechanism. It was shown that there are two factors affecting redox potential of a given metal couple: Lever’s electrochemical parameters of the ligands and the effective ionic charge of TM, which in cluster compounds differs effectively from the formal value due to the bond strains around TM atoms. Calculations of the effective ionic charge of TMs were performed in the framework of bond valence model, which relates the valence of a bond to its length by simple Pauling relationship. It was also shown that due to the bond strains the charge depends mainly on the atomic size of the inner ligands.

UVA-Degradable Collagenase Nanocapsules as a Potential Treatment for Fibrotic Diseases

Peyronie and Dupuytren are pathologies characterized by the appearance of localized fibrotic lesions in an organ. These disorders originate from an excessive production of collagen in the tissue provoking dysfunction and functional limitations to the patients. Local administration of collagenase is the most used treatment for these fibrotic-type diseases, but a high lability of the enzyme limits its therapeutic efficacy. Herein, we present a novel methodology for the preparation of collagenase nanocapsules without affecting its enzymatic activity and capable of releasing the enzyme in response to an ultraviolet A (UVA) light stimulus. Polymeric coating around collagenase was formed by free-radical polymerization of acrylamide-type monomers. Their degradation capacity under UVA irradiation was provided by incorporating a novel photocleavable acrylamide-type crosslinker within the polymeric framework. This property allowed collagenase release to be triggered in a controlled manner by employing an easily focused stimulus. Additionally, UVA irradiation presents considerable benefits by itself due to its capacity to induce collagenase production in situ. An expected synergistic effect of collagenase nanocapsules in conjunction with UVA effect may present a promising treatment for these fibrotic diseases.

The undetected loss of aged carbon from boreal mineral soils

The boreal forest is among the largest terrestrial biomes on earth, storing more carbon (C) than the atmosphere. Due to rapid climatic warming and enhanced human development, the boreal region may have begun transitioning from a net C sink to a net source. This raises serious concern that old biogenic soil C can be re-introduced into the modern C cycle in near future. Combining bio-decay experiments, mixing models and the Keeling plot method, we discovered a distinct old pre-bomb organic carbon fraction with high biodegradation rate. In total, 34 ± 12% of water-extractable organic carbon (WEOC) in podzols, one of the dominating boreal soil types, consisted of aged (~ 1000 year) labile C. The omission of this aged (i.e., Δ14C depleted) WEOC fraction in earlier studies is due to the co-occurrence with Δ14C enriched modern C formed following 1950s nuclear bomb testing masking its existence. High lability of aged soil WEOC and masking effects of modern Δ14C enriched C suggests that the risk for mobilization and re-introduction of this ancient C pool into the modern C cycle has gone undetected. Our findings have important implications for earth systems models in terms of climate-carbon feedbacks and the future C balance of the boreal forest.

Functional basis of electron transport within photosynthetic complex I

Photosynthesis and respiration rely upon a proton gradient to produce ATP. In photosynthesis, the Respiratory Complex I homologue, Photosynthetic Complex I (PS-CI) is proposed to couple ferredoxin oxidation and plastoquinone reduction to proton pumping across thylakoid membranes, and is fundamental to bioenergetics in photosynthetic bacteria and some higher plant cell types. However, little is known about the PS-CI molecular mechanism and attempts to understand its function have previously been frustrated by its large size and high lability. Here, we overcome these challenges by pushing the limits in sample size and spectroscopic sensitivity, to determine arguably the most important property of any electron transport enzyme – the reduction potentials of its cofactors, in this case the iron-sulphur clusters of PS-CI, and unambiguously assign them to the structure using double electron-electron resonance (DEER). We have thus determined the bioenergetics of the electron transfer relay and provide insight into the mechanism of PS-CI, laying the foundations for understanding of how this important bioenergetic complex functions.

Soil organic carbon stability in European mountain meadows

<p><span>Soil organic carbon (SOC) stocks play a significant role in global climate regulation. CO</span><sub><span>2</span></sub><span> fluxes between soils and atmosphere partly depend on soil organic matter (SOM) biogeochemical stability. Cold ecosystems are generally characterized by a high SOC stock, a large part of it being stabilized by environmental conditions (</span><span><em>e.g.</em></span><span> low pH and temperature). SOC stocks of cold ecosystems are also supposed to be highly vulnerable to climate change that is cancelling the stabilizing effect of low temperature on SOM.</span></p><p> </p><p><span>The aim of this study was to investigate the biogeochemical characteristics of SOM in mountain meadows at the European scale. Our goal was also to determine how environmental factors, including climate, elevation and plant functional traits could drive SOM stability and chemistry. To do so, we used the soil sample set of the ODYSSEE project (</span><span></span><span>), collected in 65 sites located in the main European’s mountains range (Alps, Pyrenees, Carpathians, Balkans). Topsoils (0–10 cm) from two plant communities (when both were present) were sampled in acidic meadows: </span><span><em>Nardetum strictae</em></span><span> and </span><span><em>Caricetum curvulae</em></span><span>. To assess SOM chemistry and biogeochemical stability, we used several indices based on Rock-Eval® 6 thermal analysis.</span></p><p> </p><p><span>The topsoil samples showed a high concentration of organic carbon (114 ± 54 gC/kg of soil), and a weakly decomposed SOM as indicated by a relatively high C:N ratio (15 ± 2.5), hydrogen content (Rock-Eval® hydrogen index = 358 ± 44 mgHC/gC) and a relatively low oxygen content (Rock-Eval® OI</span><sub><span>RE6</span></sub><span> = 151 ± 10 mgO</span><sub><span>2</span></sub><span>/gC). The decomposition state of SOM increased with mean air temperature in winter. The size of the thermally labile SOC pool was high for all samples (pyrolysable SOC = 27 to 44% of total SOC), and it strongly increased with elevation. The size of the labile SOC pool (pyrolysable SOC) was also negatively correlated to a plant functional trait: the mean height of the plant community. </span></p><p> </p><p><span>The topsoils of European mountains meadows have a high SOC content characterized by a globally high lability that further increases with elevation. The high lability of SOM revealed by Rock-Eval® 6 thermal analysis indicates a generally high vulnerability of SOC to climate change throughout European mountain meadows ecosystems.</span></p><p><span>The grass adaptative strategy developed under a cold climate induces lower plant height and higher carbon allocation to the root system. Higher carbon input to soil and/or allelopathic mechanisms protecting SOM from decomposition could possibly explain that lower plant communities of European acidic alpine meadows are characterized by a more labile SOM.</span></p>

Biological lability of Dissolved Organic Matter released by phytoplankton

<p>Phytoplankton is the primary source of Dissolved Organic Matter (DOM) to the oceans. DOM is mainly released by extracellular exudation and used by heterotrophic prokaryotes to synthesise biomass and recycle inorganic nutrients. DOM released by phytoplankton is mainly composed by carbohydrates, proteins and lipids that are thought to be labile and by humic substances that are thought to be recalcitrant and thus resistant to bacterial degradation. There are a lot of uncertainties regarding the biological lability of exudates and the role of DOM released by phytoplankton in the marine carbon cycle. In this study, cultures of the diatom P. tricornutum were produced under axenic conditions and Dissolved Organic Carbon (DOC) concentration, Excitation-Emission matrices (EEMs) and cell density were measured with time in order to follow the release of DOM during the different growth phases. Exudates were then inoculated with a marine microbial community for 24 days, DOC removal and FDOM transformation were followed with time in the exudates and in the permeate (< 3k Da; Low Molecular Weight, LMW) and retentate (> 3k Da; High Molecular Weight, HMW) fractions. Heterotrophic prokaryotes abundance was also followed during the incubations. Our results show that ~75% of the total DOC pool was LMW. After 24 days, 28% of the initial DOC pool was removed. Fluorescence indicate high lability of protein-like molecules and degradation of bigger proteins into smaller peptides before their removal. The production of humic-like and flavin-like substances was also observed.</p><p> </p>