Polyurethane (PUR) nanofabrics based on nanofibers of average diameters in the range of 250-110 nm with different meso-tetraphenylporphyrin (TPP) loading (0.01-5 wt %) were prepared by an electrospinning process. The oxygen quenching of excited states and singlet oxygen-sensitized delayed fluorescence (SODF) of TPP were studied at different oxygen pressures. We found that TPP in PUR matrix is present in monomeric state, and it is easily accessed by oxygen. Analysis of the kinetics of the TPP triplet, singlet oxygen, and SODF indicates that repopulation of TPP fluorescent state includes reaction of singlet oxygen with TPP triplets. The integrated SODF achieved more than 20% of the prompt fluorescence for nanofabric loaded with 5 wt % TPP. The dependence of SODF intensity on the TPP concentration in nanofibers is nearly quadratic.

• MeSH
• fluorescence * MeSH
• kinetika MeSH
• kyslík analýza   MeSH
• nanovlákna chemie   MeSH
• polyurethany * MeSH
• porfyriny MeSH
• singletový kyslík MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• kyslík MeSH
• polyurethany * MeSH
• porfyriny MeSH
• singletový kyslík MeSH
• tetraphenylporphyrin MeSH Prohlížeč

Formation of singlet oxygen (1O2) was reported to accompany light stress in plants, contributing to cell signaling or oxidative damage. So far, Singlet Oxygen Sensor Green (SOSG) has been the only commercialized fluorescent probe for 1O2 imaging though it suffers from several limitations (unequal penetration and photosensitization) that need to be carefully considered to avoid misinterpretation of the analysed data. Herein, we present results of a comprehensive study focused on the appropriateness of SOSG for 1O2 imaging in three model photosynthetic organisms, unicellular cyanobacteria Synechocystis sp. PCC 6803, unicellular green alga Chlamydomonas reinhardtii and higher plant Arabidopsis thaliana. Penetration of SOSG differs in both unicellular organisms; while it is rather convenient for Chlamydomonas it is restricted by the presence of mucoid sheath of Synechocystis, which penetrability might be improved by mild heating. In Arabidopsis, SOSG penetration is limited due to tissue complexity which can be increased by pressure infiltration using a shut syringe. Photosensitization of SOSG and SOSG endoperoxide formed by its interaction with 1O2 might be prevented by illumination of samples by a red light. When measured under controlled conditions given above, SOSG might serve as specific probe for detection of intracellular 1O2 formation in photosynthetic organisms.

• MeSH
• Arabidopsis metabolismus   MeSH
• barva MeSH
• Chlamydomonas reinhardtii metabolismus   MeSH
• fluorescenční barviva metabolismus   MeSH
• fotosyntéza fyziologie   MeSH
• kyslík metabolismus   MeSH
• oxidace-redukce MeSH
• singletový kyslík metabolismus   MeSH
• světlo MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• fluorescenční barviva MeSH
• kyslík MeSH
• singletový kyslík MeSH

In the current study, singlet oxygen formation by lipid peroxidation induced by heat stress (40 °C) was studied in vivo in unicellular green alga Chlamydomonas reinhardtii. Primary and secondary oxidation products of lipid peroxidation, hydroperoxide and malondialdehyde, were generated under heat stress as detected using swallow-tailed perylene derivative fluorescence monitored by confocal laser scanning microscopy and high performance liquid chromatography, respectively. Lipid peroxidation was initiated by enzymatic reaction as inhibition of lipoxygenase by catechol and caffeic acid prevented hydroperoxide formation. Ultra-weak photon emission showed formation of electronically excited species such as triplet excited carbonyl, which, upon transfer of excitation energy, leads to the formation of either singlet excited chlorophyll or singlet oxygen. Alternatively, singlet oxygen is formed by direct decomposition of hydroperoxide via Russell mechanisms. Formation of singlet oxygen was evidenced by the nitroxyl radical 2,2,6,6-tetramethylpiperidine-1-oxyl detected by electron paramagnetic resonance spin-trapping spectroscopy and the imaging of green fluorescence of singlet oxygen sensor green detected by confocal laser scanning microscopy. Suppression of singlet oxygen formation by lipoxygenase inhibitors indicates that singlet oxygen may be formed via enzymatic lipid peroxidation initiated by lipoxygenase.

• MeSH
• Chlamydomonas reinhardtii metabolismus   MeSH
• lipoxygenasa metabolismus   MeSH
• malondialdehyd metabolismus   MeSH
• peroxidace lipidů fyziologie   MeSH
• reakce na tepelný šok fyziologie   MeSH
• rostlinné proteiny metabolismus   MeSH
• singletový kyslík metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• lipoxygenasa MeSH
• malondialdehyd MeSH
• rostlinné proteiny MeSH
• singletový kyslík MeSH

Flavins are a unique class of compounds that combine the features of singlet oxygen generators and redox-dependent fluorophores. From a broad family of flavin derivatives, deazaalloxazines are significantly underdeveloped from the point of view of photophysical properties. Herein, we report photophysics of 5-deazaalloxazine (1a) in water, acetonitrile, and some other solvents. In particular, triplet excited states of 1a in water and in acetonitrile were investigated using ultraviolet-visible (UV-Vis) transient absorption spectroscopy. The measured triplet lifetimes for 1a were all on the microsecond time scale (≈ 60 μs) in deoxygenated solutions. The quantum yield of S1 → T1 intersystem crossing for 1a in water was 0.43 based on T1 energy transfer from 1a to indicaxanthin (5) acting as acceptor and on comparative actinometric measurements using benzophenone (6). 1a was an efficient photosensitizer for singlet oxygen in aerated solutions, with quantum yields of singlet oxygen in methanol of about 0.76, compared to acetonitrile ~ 0.74, dichloromethane ~ 0.64 and 1,2-dichloroethane ~ 0.54. Significantly lower singlet oxygen quantum yields were obtained in water and deuterated water (ФΔ ~ 0.42 and 0.44, respectively). Human red blood cells (RBC) were used as a cell model to study the antioxidant capacity in vitro and cytotoxic activity of 1a. Fluorescence-lifetime imaging microscopy (FLIM) data were analyzed by fluorescence lifetime parameters and distribution for different parts of the emission spectrum. Comparison of multidimensional fluorescent properties of RBC under physiological-like and oxidative-stress conditions in the presence and absence of 1a suggests its dual activity as probe and singlet-oxygen generator and opens up a pathway for using FLIM to analyze complex intracellular behavior of flavin-like compounds. These new data on structure-property relationship contribute to the body of information required for a rational design of flavin-based tools for future biological and biochemical applications.

• Klíčová slova
• 5-deazaalloxazine, 5-deazaflavin, Alloxazine, Fluorescence-lifetime imaging microscopy (FLIM), Oxidative stress, Red blood cells, Singlet oxygen, Triplet excited state,
• MeSH
• flaviny MeSH
• fotosenzibilizující látky * farmakologie   chemie   MeSH
• lidé MeSH
• organické látky MeSH
• oxidace-redukce MeSH
• singletový kyslík * chemie   MeSH
• voda chemie   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• 4,6-dinitro-o-cresol MeSH Prohlížeč
• flaviny MeSH
• fotosenzibilizující látky * MeSH
• organické látky MeSH
• singletový kyslík * MeSH
• voda MeSH

Polymeric nanofiber materials loaded with photosensitizers exhibit significant antibacterial activity due to their generation of cytotoxic singlet oxygen O(2)((1)Δ(g)). A time-gated fluorescence imaging technique was used to monitor the photosensitized processes in polystyrene (PS) and gelatin (GE) nanofibers loaded with 0.1 wt % tetraphenylporphyrin (TPP) photosensitizer. The fluorescence decay of TPP at the periphery of the PS nanofibers was single exponential. Increased fluorescence quenching was observed in the domains with higher TPP loading, located in the center of the nanofibers, and added a shorter lifetime component to the kinetics. The domains exhibiting singlet oxygen activity within the nanofibers were visualized and analyzed by singlet oxygen-sensitized delayed fluorescence imaging (SODF). Whereas O(2)((1)Δ(g)) was produced in PS nanofibers, its production in GE nanofibers was limited. These results were confirmed by time-resolved phosphorescence measurements at 1270 nm.

• MeSH
• časové faktory MeSH
• fluorescence * MeSH
• fluorescenční mikroskopie MeSH
• nanovlákna chemie   MeSH
• polymery chemie   MeSH
• povrchové vlastnosti MeSH
• singletový kyslík chemie   MeSH
• velikost částic MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• polymery MeSH
• singletový kyslík MeSH

Perylenylethynyl derivatives have been recognized as broad-spectrum antivirals that target the lipid envelope of enveloped viruses. In this study, we present novel perylenylethynylphenols that exhibit nanomolar or submicromolar antiviral activity against Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) and feline infectious peritonitis virus (FIPV) in vitro. Perylenylethynylphenols incorporate into viral and cellular membranes and block the entry of the virus into the host cell. Furthermore, these compounds demonstrate an ability to generate singlet oxygen when exposed to visible light. The rate of singlet oxygen production is positively correlated with antiviral activity, confirming that the inhibition of fusion is primarily due to singlet-oxygen-induced damage to the viral envelope. The unique combination of a shape that affords affinity to the lipid bilayer and the capacity to generate singlet oxygen makes perylenylethynylphenols highly effective scaffolds against enveloped viruses. The anticoronaviral activity of perylenylethynylphenols is strictly light-dependent and disappears in the absence of daylight (under red light). Moreover, these compounds exhibit negligible cytotoxicity, highlighting their significant potential for further exploration of the precise antiviral mechanism and the broader scope and limitations of this compound class.

• Klíčová slova
• SARS-CoV-2, antivirals, perylene, photosensitizers, singlet oxygen,
• MeSH
• antivirové látky farmakologie   MeSH
• COVID-19 * MeSH
• kočky MeSH
• membrány MeSH
• SARS-CoV-2 MeSH
• singletový kyslík * MeSH
• zvířata MeSH
• Check Tag
• kočky MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• antivirové látky MeSH
• singletový kyslík * MeSH

Reactive oxygen species (ROS) are presently thought to play important role in an increasing number of the physiological and pathological processes in living organisms. Various chemiluminescent (CL) compounds have been studied in order to find suitable and specific probes for the detection of particular ROS species. The CL of luminol is known to be non-specific and can be induced by various oxidants. Two Cypridina luciferin analogues, CLA and MCLA, have been used for the detection of ROS in vivo. CLAs are thought to emit light only when reacting with superoxide and singlet oxygen. It is possible to distinguish the particular ROS by using a specific quencher or scavenger, e.g. superoxide dismutase (SOD) or sodium azide (NaN(3)). The CL reactions of luminol (3-aminophthalhydrazide), CLA [2-methyl-6-phenyl-3,7-dihydroimidazo(1,2α) pyrazin-3-one] and MCLA [2-methyl-6-(p-methoxyphenyl)-3,7-dihydroimidazo(1,2α) pyrazin-3-one] were studied in three hydrogen peroxide decomposition systems (H(2)O(2)-HRP; H(2)O(2)-CuSO(4); and H(2)O(2)-NaOCl). The measurements were carried out in phosphate buffer, pH 7.4, at 25°C, using a luminometer (Fluoroskan Ascent FL and Sirius C). NaN(3) was used as the specific quencher of singlet oxygen. The results demonstrate that the proclaimed specificity of the CL of Cypridina luciferin analogues towards singlet oxygen has to be discussed.

• MeSH
• azid sodný chemie   MeSH
• luminiscence MeSH
• luminol chemie   MeSH
• pyraziny chemie   MeSH
• reaktivní formy kyslíku chemie   MeSH
• singletový kyslík chemie   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• 2-methyl-6-phenyl-3,7-dihydroimidazo(1,2-a)pyrazin-3-one MeSH Prohlížeč
• azid sodný MeSH
• luminol MeSH
• pyraziny MeSH
• reaktivní formy kyslíku MeSH
• singletový kyslík MeSH

A highly prospective drug for the X-ray induced photodynamic therapy (PDTX), LuAG:Pr3+@SiO2-PpIX nanocomposite, was successfully prepared by a three step process: photo-induced precipitation of the Lu3Al5O12:Pr3+ (LuAG:Pr3+) core, sol-gel technique for amorphous silica coating, and a biofunctionalization by attaching the protoporphyrin IX (PpIX) molecules. The synthesis procedure provides three-layer nanocomposite with uniform shells covering an intensely luminescent core. Room temperature radioluminescence (RT RL) spectra as well as photoluminescence (RT PL) steady-state and time resolved spectra of the material confirm the non-radiative energy transfer from the core Pr3+ ions to the PpIX outer layer. First, excitation of Pr3+ ions results in the red luminescence of PpIX. Second, the decay measurements exhibit clear evidence of mentioned non-radiative energy transfer (ET). The singlet oxygen generation in the system was demonstrated by the 3'-(p-aminophenyl) fluorescein (APF) chemical probe sensitive to the singlet oxygen presence. The RT PL spectra of an X-ray irradiated material with the APF probe manifest the formation of singlet oxygen due to which enhanced luminescence around 530 nm is observed. Quenching studies, using NaN3 as an 1O2 inhibitor, also confirm the presence of 1O2 in the system and rule out the parasitic reaction with OH radicals. To summarize, presented features of LuAG:Pr3+@SiO2-PpIX nanocomposite indicate its considerable potential for PDTX application.

• Klíčová slova
• Bioconjugates, LuAG, Nanocomposites, Photodynamic therapy, Scintillator, Singlet oxygen,
• MeSH
• fotosenzibilizující látky chemie   MeSH
• luminiscenční měření MeSH
• nanokompozity chemie   MeSH
• oxid křemičitý chemie   MeSH
• přenos energie MeSH
• protoporfyriny chemie   MeSH
• singletový kyslík metabolismus   MeSH
• transmisní elektronová mikroskopie MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• fotosenzibilizující látky MeSH
• oxid křemičitý MeSH
• protoporfyriny MeSH
• protoporphyrin IX MeSH Prohlížeč
• singletový kyslík MeSH

Photosystem II (PSII) is exposed to various abiotic stresses associated with adverse environmental conditions such as high light, heat, heavy metals or mechanical injury. Distinctive functional response to adverse environmental conditions is formation of singlet oxygen ((1)O2). In this review, recent progress on mechanistic principles on (1)O2 formation under abiotic stresses is summarized. Under high light, (1)O2 is formed by excitation energy transfer from triplet chlorophylls to molecular oxygen formed by the spin conversion via photosensitization Type II reaction in the PSII antenna complex or by the recombination of (1)[P680(+)Pheo(-)] radical pair in the PSII reaction center. Apart from well-described (1)O2 formation by excitation energy transfer, (1)O2 formation by decomposition of dioxetane and tetroxide is summarized as a potential source of (1)O2 in PSII under heat, heavy metals and mechanical stress. The description of mechanistic principles on (1)O2 formation under abiotic stress allows us to understand how plants respond to adverse environmental conditions in vivo.

• Klíčová slova
• Charge recombination, Prenyllipids, Reactive oxygen species, Singlet oxygen, Triplet chlorophyll, Xanthophylls,
• MeSH
• fotosystém II (proteinový komplex) chemie   metabolismus   MeSH
• fyziologický stres * účinky léků   účinky záření   MeSH
• oxidační stres * účinky léků   účinky záření   MeSH
• rostliny účinky léků   metabolismus   účinky záření   MeSH
• singletový kyslík metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH
• Názvy látek
• fotosystém II (proteinový komplex) MeSH
• singletový kyslík MeSH

Low temperature decreases PSII damage in vivo, confirming earlier in vitro results. Susceptibility to photoinhibition differs among Arabidopsis accessions and moderately decreases after 2-week cold-treatment. Flavonols may alleviate photoinhibition. The rate of light-induced inactivation of photosystem II (PSII) at 22 and 4 °C was measured from natural accessions of Arabidopsis thaliana (Rschew, Tenela, Columbia-0, Coimbra) grown under optimal conditions (21 °C), and at 4 °C from plants shifted to 4 °C for 2 weeks. Measurements were done in the absence and presence of lincomycin (to block repair). PSII activity was assayed with the chlorophyll a fluorescence parameter Fv/Fm and with light-saturated rate of oxygen evolution using a quinone acceptor. When grown at 21 °C, Rschew was the most tolerant to photoinhibition and Coimbra the least. Damage to PSII, judged from fitting the decrease in oxygen evolution or Fv/Fm to a first-order equation, proceeded more slowly or equally at 4 than at 22 °C. The 2-week cold-treatment decreased photoinhibition at 4 °C consistently in Columbia-0 and Coimbra, whereas in Rschew and Tenela the results depended on the method used to assay photoinhibition. The rate of singlet oxygen production by isolated thylakoid membranes, measured with histidine, stayed the same or slightly decreased with decreasing temperature. On the other hand, measurements of singlet oxygen from leaves with Singlet Oxygen Sensor Green suggest that in vivo more singlet oxygen is produced at 4 °C. Under high light, the PSII electron acceptor QA was more reduced at 4 than at 22 °C. Singlet oxygen production, in vitro or in vivo, did not decrease due to the cold-treatment. Epidermal flavonols increased during the cold-treatment and, in Columbia-0 and Coimbra, the amount correlated with photoinhibition tolerance.

• Klíčová slova
• Acclimation, Charge recombination, Chilling stress, Cold-hardening, Photodamage, Photoinactivation, Reactive oxygen species, SOSG,
• MeSH
• aklimatizace MeSH
• Arabidopsis fyziologie   účinky záření   MeSH
• chlorofyl a analýza   MeSH
• fluorescence MeSH
• fotosystém II (proteinový komplex) metabolismus   účinky záření   MeSH
• listy rostlin fyziologie   účinky záření   MeSH
• nízká teplota MeSH
• singletový kyslík metabolismus   účinky záření   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• chlorofyl a MeSH
• fotosystém II (proteinový komplex) MeSH
• singletový kyslík MeSH