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Suppression of Light-Induced Oxidative Stress in the Retina by Mitochondria-Targeted Antioxidant
摘要： Light-induced oxidation of lipids and proteins provokes retinal injuries and results in progression of degenerative retinal diseases, such as, for instance, iatrogenic photic maculopathies. Having accumulated over years retinal injuries contribute to development of age-related macular degeneration (AMD). Antioxidant treatment is regarded as a promising approach to protecting the retina from light damage and AMD. Here, we examine oxidative processes induced in rabbit retina by excessive light illumination with or without premedication using mitochondria-targeted antioxidant SkQ1 (10-(6’-plastoquinonyl)decyltriphenyl-phosphonium). The retinal extracts obtained from animals euthanized within 1–7 days post exposure were analyzed for H2O2, malondialdehyde (MDA), total antioxidant activity (AOA), and activities of glutathione peroxidase (GPx) and superoxide dismutase (SOD) using colorimetric and luminescence assays. Oxidation of visual arrestin was monitored by immunoblotting. The light exposure induced lipid peroxidation and H2O2 accumulation in the retinal cells. Unexpectedly, it prominently upregulated AOA in retinal extracts although SOD and GPx activities were compromised. These alterations were accompanied by accumulation of disulfide dimers of arrestin revealing oxidative stress in the photoreceptors. Premedication of the eyes with SkQ1 accelerated normalization of H2O2 levels and redox-status of lipids and proteins, contemporarily enhancing AOA and, likely, sustaining normal activity of GPx. Thus, SkQ1 protects the retina from light-induced oxidative stress and could be employed to suppress oxidative damage of proteins and lipids contributing to AMD.
关键词： SkQ1,superoxide dismutase,glutathione peroxidase,disulfide dimerization of proteins,visual arrestin,age-related macular degeneration,mitochondria-targeted antioxidant,antioxidant activity,light-induced retinal damage,oxidative stress
更新于2025-09-23 15:23:52
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Anthracene-Attached Persistent Tricyclic Aromatic Hydrocarbon Radicals
摘要： Anthracene-attached tricyclic aromatic hydrocarbon radicals having different central polygons, Ant-5, Ant-6, and Ant-7, were synthesized to evaluate the role of an anthracene substituent group in the stability and reactivity of tricyclic aromatic hydrocarbon radicals. The bulky anthryl group effectively protects a carbon atom with high spin density, resulting in high persistence of the radicals. On the other hand, the combination of the anthryl group and the tricyclic aromatic scaffold makes the molecular structure drastically change from a twisted form to a folded form and an unpaired electron moves into the anthryl moiety, eventually affording a tail-to-tail σ-dimer.
关键词： anthracene,mechanochlomism,persistent radical,dimerization,hydrocarbon radical
更新于2025-09-23 15:23:52
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A novel donor-π-acceptor anthracene monomer: Towards faster and milder reversible dimerization
摘要： A novel functional 2,6-substituted donor-acceptor anthracene derivative, bearing a long alkyl spacer and a polymerizable end-group, is synthesized from readily available compounds. This monomer possesses conjugated electron donor and acceptor moieties to achieve UV absorption and anthracene dimerization at higher wavelengths and under milder conditions, than anthracene and other reported anthracene derivatives. The compound was shown to absorb at higher wavelengths and dimerize much faster compared to most 9-substituted anthracenes. The fast photochemical and relatively slow thermal scission of the dimers were studied and related to the chemical structure, i.e. the 2,6-substitution.
关键词： 6-substituted,2,dimerization,scission.,Anthracene derivatives
更新于2025-09-23 15:22:29
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Influence of the N-terminal segment and the PHY-tongue element on light-regulation in bacteriophytochromes
摘要： Photoreceptors enable the integration of ambient light stimuli to trigger lifestyle adaptations via modulation of central metabolite levels involved in diverse regulatory processes. Red light sensing bacteriophytochromes are attractive targets for the development of innovative optogenetic tools due to their natural modularity, diverse functionalities and the natural availability of the light-absorbing biliverdin in animal tissues. However, a rational design of such tools is complicated by the poor understanding of molecular mechanisms of light signal transduction over long distances – from the site of photon absorption to the active site of downstream enzymatic effectors. Here we show how swapping structural elements between two bacteriophytochrome homologs provides additional insights into light signal integration and effector regulation, involving a fine-tuned interplay of important structural elements of the sensor as well as the sensor-effector linker. Facilitated by the availability of structural information of inhibited and activated full-length structures of one of the two homologs (Idiomarina species A28L Phytochrome-activated diguanylyl Cyclase - IsPadC) and characteristic differences in photoresponses of the two homologs, we identify an important cross-talk between the N-terminal segment (NTS), containing the covalent attachment site of the chromophore, and the PHY-tongue region. Moreover, we highlight how these elements influence the dynamic range of photoactivation and how activation can be improved to light/dark ratios of ~800-fold by reducing basal dark-state activities at the same time as increasing photoconversion in the light-state. This will enable future optimization of optogenetic tools aiming at a direct allosteric regulation of enzymatic effectors.
关键词： phytochrome,diguanylate cyclase,photobiology,signal transduction,bilin,GGDEF,dimerization,photoreceptor
更新于2025-09-19 17:15:36
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Plasmon–Induced Dimerization of Thiazolidine-2, 4-Dione on Silver Nanoparticles - Revealed by Surface-Enhanced Raman Scattering Study
摘要： Surface-enhanced Raman scattering (SERS) study carried on thiazolidine-2, 4-dione (TZD), pharmacologically active heterocyclic compound, points to the presence of TZD dimer formed by plasmon-induced dimerization reaction of TZD on the surface of silver nanoparticles (Ag NP) at TZD concentrations of 10-3 M and above. The evidence for the presence of dimer was obtained from the appearance of a prominent band at 1566 cm-1 corresponding to ν C=C band (a characteristic vibrational band observed for the Knoevenagel condensation reaction products) which is absent in the normal Raman scattering (NRS) spectra of TZD solid/solution. The observed spectrum compares well with the calculated spectrum of dimer obtained using density functional theory (DFT) calculations. The dimerization reaction is plausibly induced by the transfer of hot electrons generated by the non-radiative plasmon decay of Ag NP and the proposed reaction mechanism is discussed. However, at lower concentrations (10-4 to 10-6M), the characteristic dimer peak (1566 cm-1) is absent and the SERS spectra resemble more with the NRS spectrum of TZD with few changes. The spectral analysis supported by DFT calculations showed that TZD molecules undergo deprotonation and get adsorbed on Ag NP surface as enolate forms. The proximity of TZD molecules on the surface of Ag NP is a necessary factor for the dimerization to occur. At lower concentrations, most molecules lie apart and reactions between molecules become less feasible and they remain as monomers on the surface, while at higher concentrations the molecules are closer to each other on Ag NP surface favouring the dimerization reaction to take place leading to the formation of the dimer.
关键词： density functional theory,thiazolidine-2, 4-dione,silver nanoparticles,plasmon-induced dimerization,Surface-enhanced Raman scattering
更新于2025-09-19 17:13:59
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A Plasmonic Approach to Study Protein Interaction Kinetics through the Dimerization of Functionalized Ag Nanoparticles
摘要： Understanding the kinetics of protein interactions plays a key role in biology with significant implications for the design of analytical methods for disease monitoring and diagnosis in medical care, research and industrial applications. Herein, we introduce a novel plasmonic approach to study the binding kinetics of protein-ligand interactions following the formation of silver nanoparticles (Ag nps) dimers by UV-Vis spectroscopy that can be used as probes for antigen detection and quantification. to illustrate and test the method, the kinetics of the prototype biotin-streptavidin (Biot-StV) pair interaction was studied. controlled aggregates (dimers) of StV functionalized Ag nps were produced by adding stoichiometric quantities of gliadin-specific biotinylated antibodies (IgG-Biot). The dimerization kinetics was studied in a systematic way as a function of Ag NPs size and at different concentrations of IgG-Biot. The kinetics data have shown to be consistent with a complex reaction mechanism in which only the Ag NPs attached to the IgG-Biot located in a specific STV site are able to form dimers. These results help in elucidating a complex reaction mechanism involved in the dimerization kinetics of functionalized Ag nps, which can serve as probes in surface plasmon resonance-based bioassays for the detection and quantification of different biomarkers or analytes of interest.
关键词： biotin-streptavidin interaction,silver nanoparticles,dimerization,protein interaction kinetics,plasmonic approach,surface plasmon resonance,UV-Vis spectroscopy
更新于2025-09-11 14:15:04
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π-Dimerization ability of conjugated oligomer dication diradicaloids composed of dithienylpyrrole and benzodithiophene units
摘要： 2+ composed of 2,5- di(2- thienyl)- N- 2+ and 2 Stable conjugated oligomer dications 1 methylpyrrole (DTP) units at the both ends of the π- systems with methoxy substitu- ents at the 3- position of thienyl units and methylthio end- capping group and benzo[2,1- b:3,4- b′]dithiophene (BDT) unit(s) at the central part with sterically de- manding phenyl substituents were synthesized. From DFT calculations and ESR ex- 2+ was reduced periments, it was concluded that the diradical character in 1 in comparison with the radical character of their reference compound 3·+ composed 2+ was considered to have a of one DTP and one BDT units. In addition, the shorter 1 2+. Nevertheless, judging from the re- further lower diradical character than that of 2 2+ showed a comparable π- 2+ and 2 sults of VT- UV- vis- NIR measurements, both 1 dimerization ability at the DTP moiety in dichloromethane solution with 3·+.
关键词： dithienylpyrrole,diradicaloids,conjugated oligomer dications,benzodithiophene,π- Dimerization
更新于2025-09-10 09:29:36
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Light-dependent suppression of COP1 multimeric complex formation is determined by the blue-light receptor FKF1 in Arabidopsis
摘要： CONSTITUTIVELY PHOTOMORPHOGENIC1 (COP1), a multifunctional E3 ligase protein with many target proteins, is involved in diverse developmental processes throughout the plant's lifecycle, including seed germination, the regulation of circadian rhythms, photomorphogenesis, and the control of flowering time. To function, COP1 must form multimeric complexes with SUPPRESSOR OF PHYA1 (SPA1), i.e., [(COP1)2(SPA1)2] tetramers. We recently reported that the blue-light receptor FKF1 (FLAVIN-BINDING, KELCH REPEAT, F-BOX1) represses COP1 activity by inhibiting its homodimerization, but it is not yet clear whether FKF1 affects the formation of COP1-containing multimeric complexes. To explore this issue, we performed size exclusion chromatography (SEC) of Arabidopsis thaliana proteins and found that the levels and composition of COP1-containing multimeric complexes varied throughout a 24-h period. The levels of 440e669 kDa complexes were dramatically reduced in the late afternoon compared to the morning and at night in wild-type plants. During the daytime, the levels of these complexes were reduced in FKF1-overexpressing plants but not in fkf1-t, a loss-of-function mutant of FKF1, suggesting that FKF1 is closely associated with the destabilization of COP1 multimeric protein complexes in a light-dependent manner. We also analyzed the SEC patterns of COP1 multimeric complexes in transgenic plants overexpressing mutant COP1 variants, including COP1L105A (which forms homodimers) and COP1L170A (which cannot form homodimers), and found that COP1 multimeric complexes were scarce in plants overexpressing COP1L170A. These results indicate that COP1 homodimers serve as basic building blocks that assemble into COP1 multimeric complexes with diverse target proteins. We propose that light-activated FKF1 inhibits COP1 homodimerization, mainly by destabilizing 440e669 kDa COP1 complexes, resulting in the repression of CONSTANS-degrading COP1 activity in the late afternoon in long days, but not in short days, thereby regulating photoperiodic flowering in Arabidopsis.
关键词： Dimerization,Arabidopsis,Multimeric protein complex,COP1,Photoperiodic flowering,FKF1
更新于2025-09-09 09:28:46