Photosynthetic organisms harvest light for energy. Some eukaryotic algae have specialized in harvesting far-red light by tuning chlorophyll a absorption through a mechanism still to be elucidated. Here, we combined optically detected magnetic resonance and pulsed electron paramagnetic resonance measurements on red-adapted light-harvesting complexes, rVCP, isolated from the freshwater eustigmatophyte alga Trachydiscus minutus to identify the location of the pigments responsible for this remarkable adaptation. The pigments have been found to belong to an excitonic cluster of chlorophylls a at the core of the complex, close to the central carotenoids in L1/L2 sites. A pair of structural features of the Chl a403/a603 binding site, namely the histidine-to-asparagine substitution in the magnesium-ligation residue and the small size of the amino acid at the i-4 position, resulting in a [A/G]xxxN motif, are proposed to be the origin of this trait. Phylogenetic analysis of various eukaryotic red antennae identified several potential LHCs that could share this tuning mechanism. This knowledge of the red light acclimation mechanism in algae is a step towards rational design of algal strains in order to enhance light capture and efficiency in large-scale biotechnology applications.
- MeSH
- chlorofyl a * metabolismus chemie MeSH
- chlorofyl metabolismus MeSH
- elektronová paramagnetická rezonance MeSH
- fylogeneze MeSH
- světlo MeSH
- světlosběrné proteinové komplexy * metabolismus genetika chemie MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- chlorofyl a * MeSH
- chlorofyl MeSH
- světlosběrné proteinové komplexy * MeSH
Na-V-P-Nb-based materials have gained substantial recognition as cathode materials in high-rate sodium-ion batteries due to their unique properties and compositions, comprising both alkali and transition metal ions, which allow them to exhibit a mixed ionic-polaronic conduction mechanism. In this study, the impact of introducing two transition metal oxides, V2O5 and Nb2O5, on the thermal, (micro)structural, and electrical properties of the 35Na2O-25V2O5-(40 - x)P2O5 - xNb2O5 system is examined. The starting glass shows the highest values of DC conductivity, σDC, reaching 1.45 × 10-8 Ω-1 cm-1 at 303 K, along with a glass transition temperature, Tg, of 371 °C. The incorporation of Nb2O5 influences both σDC and Tg, resulting in non-linear trends, with the lowest values observed for the glass with x = 20 mol%. Electron paramagnetic resonance measurements and vibrational spectroscopy results suggest that the observed non-monotonic trend in σDC arises from a diminishing contribution of polaronic conductivity due to the decrease in the relative number of V4+ ions and the introduction of Nb2O5, which disrupts the predominantly mixed vanadate-phosphate network within the starting glasses, consequently impeding polaronic transport. The mechanism of electrical transport is investigated using the model-free Summerfield scaling procedure, revealing the presence of mixed ionic-polaronic conductivity in glasses where x < 10 mol%, whereas for x ≥ 10 mol%, the ionic conductivity mechanism becomes prominent. To assess the impact of the V2O5 content on the electrical transport mechanism, a comparative analysis of two analogue series with varying V2O5 content (10 and 25 mol%) is conducted to evaluate the extent of its polaronic contribution.
- Klíčová slova
- (micro)structure–property relationship, EPR, PXRD, SEM-EDS, electrical properties, impedance spectroscopy, phosphate glasses, phosphate glass–ceramics, vibrational spectroscopy,
- MeSH
- elektronová paramagnetická rezonance MeSH
- fosfáty * chemie MeSH
- ionty MeSH
- keramika chemie MeSH
- niob * MeSH
- sklo chemie MeSH
- sodík chemie MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- fosfáty * MeSH
- ionty MeSH
- niob * MeSH
- sodík MeSH
- sodium phosphate MeSH Prohlížeč
- sodium polymetaphosphate MeSH Prohlížeč
Tools for radiation exposure reconstruction are required to support the medical management of radiation victims in radiological or nuclear incidents. Different biological and physical dosimetry assays can be used for various exposure scenarios to estimate the dose of ionizing radiation a person has absorbed. Regular validation of the techniques through inter-laboratory comparisons (ILC) is essential to guarantee high quality results. In the current RENEB inter-laboratory comparison, the performance quality of established cytogenetic assays [dicentric chromosome assay (DCA), cytokinesis-block micronucleus assay (CBMN), stable chromosomal translocation assay (FISH) and premature chromosome condensation assay (PCC)] was tested in comparison to molecular biological assays [gamma-H2AX foci (gH2AX), gene expression (GE)] and physical dosimetry-based assays [electron paramagnetic resonance (EPR), optically or thermally stimulated luminescence (LUM)]. Three blinded coded samples (e.g., blood, enamel or mobiles) were exposed to 0, 1.2 or 3.5 Gy X-ray reference doses (240 kVp, 1 Gy/min). These doses roughly correspond to clinically relevant groups of unexposed to low exposed (0-1 Gy), moderately exposed (1-2 Gy, no severe acute health effects expected) and highly exposed individuals (>2 Gy, requiring early intensive medical care). In the frame of the current RENEB inter-laboratory comparison, samples were sent to 86 specialized teams in 46 organizations from 27 nations for dose estimation and identification of three clinically relevant groups. The time for sending early crude reports and more precise reports was documented for each laboratory and assay where possible. The quality of dose estimates was analyzed with three different levels of granularity, 1. by calculating the frequency of correctly reported clinically relevant dose categories, 2. by determining the number of dose estimates within the uncertainty intervals recommended for triage dosimetry (±0.5 Gy or ±1.0 Gy for doses <2.5 Gy or >2.5 Gy), and 3. by calculating the absolute difference (AD) of estimated doses relative to the reference doses. In total, 554 dose estimates were submitted within the 6-week period given before the exercise was closed. For samples processed with the highest priority, earliest dose estimates/categories were reported within 5-10 h of receipt for GE, gH2AX, LUM, EPR, 2-3 days for DCA, CBMN and within 6-7 days for the FISH assay. For the unirradiated control sample, the categorization in the correct clinically relevant group (0-1 Gy) as well as the allocation to the triage uncertainty interval was, with the exception of a few outliers, successfully performed for all assays. For the 3.5 Gy sample the percentage of correct classifications to the clinically relevant group (≥2 Gy) was between 89-100% for all assays, with the exception of gH2AX. For the 1.2 Gy sample, an exact allocation to the clinically relevant group was more difficult and 0-50% or 0-48% of the estimates were wrongly classified into the lowest or highest dose categories, respectively. For the irradiated samples, the correct allocation to the triage uncertainty intervals varied considerably between assays for the 1.2 Gy (29-76%) and 3.5 Gy (17-100%) samples. While a systematic shift towards higher doses was observed for the cytogenetic-based assays, extreme outliers exceeding the reference doses 2-6 fold were observed for EPR, FISH and GE assays. These outliers were related to a particular material examined (tooth enamel for EPR assay, reported as kerma in enamel, but when converted into the proper quantity, i.e. to kerma in air, expected dose estimates could be recalculated in most cases), the level of experience of the teams (FISH) and methodological uncertainties (GE). This was the first RENEB ILC where everything, from blood sampling to irradiation and shipment of the samples, was organized and realized at the same institution, for several biological and physical retrospective dosimetry assays. Almost all assays appeared comparably applicable for the identification of unexposed and highly exposed individuals and the allocation of medical relevant groups, with the latter requiring medical support for the acute radiation scenario simulated in this exercise. However, extreme outliers or a systematic shift of dose estimates have been observed for some assays. Possible reasons will be discussed in the assay specific papers of this special issue. In summary, this ILC clearly demonstrates the need to conduct regular exercises to identify research needs, but also to identify technical problems and to optimize the design of future ILCs.
Reactive oxygen species play a key role in cellular homeostasis and redox signaling at physiological levels, where excessive production affects the function and integrity of macromolecules, specifically proteins. Therefore, it is important to define radical-mediated proteotoxic stress in macrophages and identify target protein to prevent tissue dysfunction. A well employed, THP-1 cell line was utilized as in vitro model to study immune response and herein we employ immuno-spin trapping technique to investigate radical-mediated protein oxidation in macrophages. Hydroxyl radical formation along macrophage differentiation was confirmed by electron paramagnetic resonance along with confocal laser scanning microscopy using hydroxyphenyl fluorescein. Lipid peroxidation product, malondialdehyde, generated under experimental conditions as detected using swallow-tailed perylene derivative fluorescence observed by confocal laser scanning microscopy and high-performance liquid chromatography, respectively. The results obtained from this study warrant further corroboration and study of specific proteins involved in the macrophage activation and their role in inflammations.
- Klíčová slova
- All-trans retinoic acid, Lipid peroxidation, Lipopolysaccharide, Macrophage, Malondialdehyde, Phorbol 12-myristate 13-acetate, Protein oxidation, Reactive oxygen species,
- MeSH
- elektronová paramagnetická rezonance metody MeSH
- makrofágy * metabolismus MeSH
- proteiny * chemie MeSH
- reaktivní formy kyslíku metabolismus MeSH
- spin trapping metody MeSH
- volné radikály analýza metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- proteiny * MeSH
- reaktivní formy kyslíku MeSH
- volné radikály MeSH
Detailed information on the photo-generated triplet states of diatom and haptophyte Fucoxanthin Chlorophyll-binding Proteins (FCPs and E-FCPs, respectively) have been obtained from a combined spectroscopic investigation involving Transient Absorption and Time-Resolved Electron Paramagnetic Resonance. Pennate diatom Phaeodactylum tricornutum FCP shows identical photoprotective Triplet-Triplet Energy Transfer (TTET) pathways to the previously investigated centric diatom Cyclotella meneghiniana FCP, with the same two chlorophyll a-fucoxanthin pairs that involve the fucoxanthins in sites Fx301 and Fx302 contributing to TTET in both diatom groups. In the case of the haptophyte Emilianina huxleyi E-FCP, only one of the two chlorophyll a-fucoxanthins pairs observed in diatoms, the one involving chlorophyll a409 and Fx301, has been shown to be active in TTET. Furthermore, despite the marked change in the pigment content of E-FCP with growth light intensity, the TTET pathway is not affected. Thus, our comparative investigation of FCPs revealed a photoprotective TTET pathway shared within these classes involving the fucoxanthin in site Fx301, a site exposed to the exterior of the antenna monomer that has no equivalent in Light-Harvesting Complexes from the green lineage.
- Klíčová slova
- Carotenoid, Diatom, Emiliania huxleyi, Light-harvesting complex, Photoprotection, TR-EPR,
- MeSH
- chlorofyl a metabolismus MeSH
- chlorofyl metabolismus MeSH
- elektronová paramagnetická rezonance MeSH
- přenos energie MeSH
- proteiny vázající chlorofyl * chemie MeSH
- rozsivky * chemie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- chlorofyl a MeSH
- chlorofyl MeSH
- fucoxanthin MeSH Prohlížeč
- proteiny vázající chlorofyl * MeSH
A magnetophotoselection (MPS) investigation of the photoexcited triplet state of chlorophyll a both in a frozen organic solvent and in a protein environment, provided by the water-soluble chlorophyll protein (WSCP) of Lepidium virginicum, is reported. The MPS experiment combines the photoselection achieved by exciting with linearly polarized light with the magnetic selection of electron paramagnetic resonance (EPR) spectroscopy, allowing the determination of the relative orientation of the optical transition dipole moment and the zero-field splitting tensor axes in both environments. We demonstrate the robustness of the proposed methodology for a quantitative description of the excitonic interactions among pigments. The orientation of the optical transition dipole moments determined by the EPR analysis in WSCP, identified as an appropriate model system, are in excellent agreement with those calculated in the point-dipole approximation. In addition, MPS provides information on the electronic properties of the triplet state, localized on a single chlorophyll a pigment of the protein cluster, in terms of orientation of the zero-field splitting tensor axes in the molecular frame.
- Klíčová slova
- TR-EPR, chlorophyll-binding protein, excitonic interaction, magnetophotoselection, triplet state,
- MeSH
- chlorofyl a metabolismus MeSH
- chlorofyl * chemie MeSH
- elektronová paramagnetická rezonance MeSH
- Lepidium * metabolismus MeSH
- světlosběrné proteinové komplexy chemie MeSH
- voda chemie MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- chlorofyl a MeSH
- chlorofyl * MeSH
- světlosběrné proteinové komplexy MeSH
- voda MeSH
The photoexcited triplet state of the "primary donors" in the two photosystems of oxygenic photosynthesis has been investigated by means of electron-nuclear double resonance (ENDOR) at Q-band (34 GHz). The data obtained represent the first set of 1H hyperfine coupling tensors of the 3P700 triplet state in PSI and expand the existing data set for 3P680. We achieved an extensive assignment of the observed electron-nuclear hyperfine coupling constants (hfcs) corresponding to the methine α-protons and the methyl group β-protons of the chlorophyll (Chl) macrocycle. The data clearly confirm that in both photosystems the primary donor triplet is located on one specific monomeric Chl at cryogenic temperature. In comparison to previous transient ENDOR and pulse ENDOR experiments at standard X-band (9-10 GHz), the pulse Q-band ENDOR spectra demonstrate both improved signal-to-noise ratio and increased resolution. The observed ENDOR spectra for 3P700 and 3P680 differ in terms of the intensity loss of lines from specific methyl group protons, which is explained by hindered methyl group rotation produced by binding site effects. Contact analysis of the methyl groups in the PSI crystal structure in combination with the ENDOR analysis of 3P700 suggests that the triplet is located on the Chl a' (PA) in PSI. The results also provide additional evidence for the localization of 3P680 on the accessory ChlD1 in PSII.
- Klíčová slova
- Chlorophyll triplet state, ENDOR, P680, P700, Spin density distribution, Triplet EPR,
- MeSH
- chlorofyl a MeSH
- elektronová paramagnetická rezonance MeSH
- fotosyntéza MeSH
- fotosystém I (proteinový komplex) * MeSH
- protony * MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- chlorofyl a MeSH
- fotosystém I (proteinový komplex) * MeSH
- protony * MeSH
Free radical-mediated activation of inflammatory macrophages remains ambiguous with its limitation to study within biological systems. U-937 and HL-60 cell lines serve as a well-defined model system known to differentiate into either macrophages or dendritic cells in response to various chemical stimuli linked with reactive oxygen species (ROS) production. Our present work utilizes phorbol 12-myristate-13-acetate (PMA) as a stimulant, and factors such as concentration and incubation time were considered to achieve optimized differentiation conditions. ROS formation likely hydroxyl radical (HO●) was confirmed by electron paramagnetic resonance (EPR) spectroscopy combined with confocal laser scanning microscopy (CLSM). In particular, U-937 cells were utilized further to identify proteins undergoing oxidation by ROS using anti-DMPO (5,5-dimethyl-1-pyrroline N-oxide) antibodies. Additionally, the expression pattern of NADPH Oxidase 4 (NOX4) in relation to induction with PMA was monitored to correlate the pattern of ROS generated. Utilizing macrophages as a model system, findings from the present study provide a valuable source for expanding the knowledge of differentiation and protein expression dynamics.
- Klíčová slova
- HL-60 cells, NADPH oxidase, NOX4, U-937 cells, macrophages, phorbol 12-myristate 13-acetate, protein-centered radicals,
- MeSH
- acetofenony farmakologie MeSH
- barvení a značení MeSH
- buněčná diferenciace * účinky léků MeSH
- elektronová paramagnetická rezonance MeSH
- HL-60 buňky MeSH
- hydroxylový radikál MeSH
- lidé MeSH
- monocyty cytologie účinky léků metabolismus MeSH
- NADP metabolismus MeSH
- proliferace buněk účinky léků MeSH
- proteiny metabolismus MeSH
- tetradekanoylforbolacetát farmakologie MeSH
- tvar buňky účinky léků MeSH
- U937 buňky MeSH
- viabilita buněk účinky léků MeSH
- volné radikály metabolismus MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- acetofenony MeSH
- acetovanillone MeSH Prohlížeč
- hydroxylový radikál MeSH
- NADP MeSH
- proteiny MeSH
- tetradekanoylforbolacetát MeSH
- volné radikály MeSH
Nanoscale magnetic systems play a decisive role in areas ranging from biology to spintronics. Although, in principle, THz electron paramagnetic resonance (EPR) provides high-resolution access to their properties, lack of sensitivity has precluded realizing this potential. To resolve this issue, the principle of plasmonic enhancement of electromagnetic fields that is used in electric dipole spectroscopies with great success is exploited, and a new type of resonators for the enhancement of THz magnetic fields in a microscopic volume is proposed. A resonator composed of an array of diabolo antennas with a back-reflecting mirror is designed and fabricated. Simulations and THz EPR measurements demonstrate a 30-fold signal increase for thin film samples. This enhancement factor increases to a theoretical value of 7500 for samples confined to the active region of the antennas. These findings open the door to the elucidation of fundamental processes in nanoscale samples, including junctions in spintronic devices or biological membranes.
- Klíčová slova
- 2D resonators, electron paramagnetic resonance, nanostructures, plasmonic metasurfaces, self-assembled monolayers, spintronics, thin layers,
- MeSH
- design vybavení metody MeSH
- elektromagnetická pole MeSH
- elektronová paramagnetická rezonance přístrojové vybavení MeSH
- nanotechnologie MeSH
- počítačová simulace MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
This study compared dexmedetomidine or xylazine in combination with tiletamine-zolazepam for chemical immobilization of wild fallow deer (Dama dama) in a prospective, randomized, blinded clinical study. Forty fallow deer were divided into two groups: tiletamine-zolazepam-xylazine (TZX) and tiletamine-zolazepam-dexmedetomidine (TZD). The TZX group was immobilized with 1.9 ± 0.05 mg/kg of xylazine and 1.48 ± 0.05 mg/kg of tiletamine-zolazepam, whereas the TZD group was immobilized with 34.15 ± 1.1 µg/kg of dexmedetomidine and 0.97 ± 0.03 mg/kg of tiletamine-zolazepam by dart. The induction time was recorded. During the immobilization, heart rate, respiratory rate, body temperature, hemoglobin oxygen saturation, blood lactate concentration, and quality of immobilization were recorded at 10, 20, and 30 m after drug administration. The time of achievement of sternal recumbency and that of standing were also recorded. The TZD group showed a significantly shorter induction time (8 ± 1.6 m, TZX group; 4 ± 0.5 m, TZD group), significantly higher quality of immobilization score (2[1-2], TZX group; 4[4-4], TZD group), and significantly lower lactate levels (5[3-7] mmol/L, TZX group; 2[1-3] mmol/L, TZD group). The time to sternal recumbency was 7 ± 1.6 m (TZX group) and 4 ± 0.5 m (TZD group), and time to quadrupedal standing was 20 ± 1.6 m (TZX group) and 16 ± 0.8 m (TZD group) (P = 0.001). Dexmedetomidine combined with tiletamine-zolazepam is a viable alternative to xylazine for the chemical immobilization of fallow deer.
- MeSH
- anestetika disociativní MeSH
- dexmedetomidin * farmakologie MeSH
- elektronová paramagnetická rezonance veterinární MeSH
- imobilizace veterinární MeSH
- prospektivní studie MeSH
- tiletamin * MeSH
- xylazin farmakologie MeSH
- zolazepam MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- randomizované kontrolované studie veterinární MeSH
- Názvy látek
- anestetika disociativní MeSH
- dexmedetomidin * MeSH
- tiletamin * MeSH
- xylazin MeSH
- zolazepam MeSH
