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1.
Blue diode‐based pulse amplitude modulation (PAM) technology can be used to measure the photosynthetic electron transport rate (ETR) in a purple nonsulfur anoxygenic photobacterium, Afifella (Rhodopseudomonas) marina. Rhodopseudomonads have a reaction center light harvesting antenna complex containing an RC‐2 type bacteriochlorophyll a protein (BChl a RC‐2‐LH1) which has a blue absorption peak and variable fluorescence similar to PSII. Absorptance of cells filtered onto glass fiber disks was measured using a blue–diode‐based absorptance meter (Blue‐RAT) so that absolute ETR could be calculated from PAM experiments. Maximum quantum yield (Y) was ≈0.6, decreasing exponentially as irradiance increased. ETR vs irradiance (P vs E) curves fitted the waiting‐in‐line model (ETR = (ETRmax × E/Eopt) × exp(1 ? E/Eopt)). Maximum ETR (ETRmax) was ≈1000–2000 μmol e? mg?1 BChl a h?1. Fe2+, bisulfite and thiosulfate act as photosynthetic electron donors. Optimum irradiance was ≈100 μmol m?2 s?1 PPFD even in Afifella grown in sunlight. Quantum efficiencies (α) were ≈0.3–0.4 mol e? mol hλ?1; or ≈11.8 ± 2.9 mol e? mol hλ?1 m2 μg?1 BChl a). An underlying layer of Afifella in a constructed algal/photosynthetic bacterial mat has little effect on the measured ETR of the overlying oxyphotoautotroph (Chlorella). 相似文献
2.
Richard Breia Sónia Vieira Jorge Marques da Silva Hernâni Gerós Ana Cunha 《Photochemistry and photobiology》2013,89(3):579-585
Grape berry development and ripening depends mainly on imported photosynthates from leaves, however, fruit photosynthesis may also contribute to the carbon economy of the fruit. In this study pulse amplitude modulated chlorophyll fluorescence imaging (imaging‐PAM) was used to assess photosynthetic properties of tissues of green grape berries. In particular, the effect of the saturation pulse (SP) intensity was investigated. A clear tissue‐specific distribution pattern of photosynthetic competence was observed. The exocarp revealed the highest photosynthetic capacity and the lowest susceptibility to photoinhibition, and the mesocarp exhibited very low fluorescence signals and photochemical competence. Remarkably, the seed outer integument revealed a photosynthetic ability similar to that of the exocarp. At a SP intensity of 5000 μmol m?2 s?1 several photochemical parameters were decreased, including maximum fluorescence in dark‐adapted (Fm) and light‐adapted (F'm) samples and effective quantum yield of PSII (ΦII), but the inner tissues were susceptible to a SP intensity as low as 3200 μmol m?2 s?1 under light‐adapted conditions, indicating a photoinhibitory interaction between SP and actinic light intensities and repetitive exposure to SP. These results open the way to further studies concerning the involvement of tissue‐specific photosynthesis in the highly compartmentalized production and accumulation of organic compounds during grape berry development. 相似文献
3.
Measurement of Photosynthesis Using PAM Technology in a Purple Sulfur Bacterium Thermochromatium tepidum (Chromatiaceae)
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We demonstrate that Blue‐diode‐based pulse amplitude modulation (PAM) technology can be used to measure the photosynthetic electron transport rate (ETR) of purple sulfur bacteria (Thermochromatium tepidum, Chromatiaceae). Previous studies showed that PAM technology could be used to estimate photosynthesis in purple nonsulfur bacteria and so PAM technology can be used to estimate photosynthesis of both kinds of purple photosynthetic bacteria. The absorptance of Thermochromatium films on glass fiber disks was measured and used to calculate actual ETR. ETR vs Irradiance (P vs E) curves fitted the waiting‐in‐line model (ETR = (ETRmax × E/Eopt) × exp (1?E/Eopt)). Yield (Y) was only ≈ 0.3–0.4. Thermochromatium saturates at 325 ± 13.8 μmol photons m?2 s?1 or ≈15% sunlight and shows photoinhibition at high irradiances. A pond of Thermochromatium would exhibit classic surface inhibition. Photosynthesis is extremely low in the absence of an electron source: ETR increases in the presence of acetate (5 mol m?3) provided as an organic carbon source and also increases in the presence of sulfite (3 mol m?3) but not sulfide and is only marginally increased by the presence of Fe2+. Nonphotochemical quenching does occur in Thermochromatium but at very low levels compared to oxygenic photo‐organisms or Rhodopseudomonads. 相似文献
4.
Raymond J. Ritchie 《Photochemistry and photobiology》2013,89(5):1143-1162
Photosynthetic bacteria are attractive for biotechnology because they produce no oxygen and so H2‐production is not inhibited by oxygen as occurs in oxygenic photoorganisms. Rhodopseudomonas palustris and Afifella marina containing BChl a can use irradiances from violet near‐UV (VNUV) to orange (350–650 nm) light and near‐infrared (NIR) light (762–870 nm). Blue diode‐based pulse amplitude modulation technology was used to measure their photosynthetic electron transport rate (ETR). ETR vs Irradiance curves fitted the waiting‐in‐line model—ETR = (ETRmax × E/Eopt) × exp (1 ? E/Eopt). The equation was integrated over pond depth to calculate ETR of Afifella and Rhodopseudomonas in a pond up to 30 cm deep (A376, 1 cm = 0.1). Afifella saturates at low irradiances and so photoinhibition results in very low photosynthesis in a pond. Rhodopseudomonas saturates at ≈15% sunlight and shows photoinhibition in the surface layers of the pond. Total ETR is ≈335 μmol (e?) m?2 s?1 in NUV + photosynthetically active radiation light (350–700 nm). Daily ETR curves saturate at low irradiances and have a square‐wave shape: ≈11–13 mol (e?) m?2 day?1 (350–700 nm). Up to 20–24% of daily 350–700 nm irradiance can be converted into ETR. NIR is absorbed by water and so competes with the bacterial RC‐2 photosystem for photons. 相似文献
5.
Miao‐Ken Hung Kuen‐Wei Tsai Sunil Sharma Jun‐Yi Wu Show‐An Chen 《Angewandte Chemie (International ed. in English)》2019,58(33):11317-11323
We propose the novel σ–π conjugated polymer poly(biphenyl germanium) grafted with two electron‐donating acridan moieties on the Ge atom for use as the host material in a polymer light‐emitting diode (PLED) with the sky‐blue‐emitting thermally activated delayed fluorescence (TADF) material DMAC‐TRZ as the guest. Its high triplet energy (ET) of 2.86 eV is significantly higher than those of conventional π–π conjugated polymers (ET=2.65 eV as the limit) and this guest emitter (ET=2.77 eV). The TADF emitter emits bluer emission than in other host materials owing to the low orientation polarizability of the germanium‐based polymer host. The Ge atom also provides an external heavy‐atom effect, which increases the rate of reverse intersystem crossing in this TADF guest, so that more triplet excitons are harvested for light emission. The sky‐blue TADF electroluminescence with this host/guest pair gave a record‐high external quantum efficiency of 24.1 % at maximum and 22.8 % at 500 cd m?2. 相似文献
6.
Miao‐Ken Hung Kuen‐Wei Tsai Sunil Sharma Jun‐Yi Wu Show‐An Chen 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(33):11439-11445
We propose the novel σ–π conjugated polymer poly(biphenyl germanium) grafted with two electron‐donating acridan moieties on the Ge atom for use as the host material in a polymer light‐emitting diode (PLED) with the sky‐blue‐emitting thermally activated delayed fluorescence (TADF) material DMAC‐TRZ as the guest. Its high triplet energy (ET) of 2.86 eV is significantly higher than those of conventional π–π conjugated polymers (ET=2.65 eV as the limit) and this guest emitter (ET=2.77 eV). The TADF emitter emits bluer emission than in other host materials owing to the low orientation polarizability of the germanium‐based polymer host. The Ge atom also provides an external heavy‐atom effect, which increases the rate of reverse intersystem crossing in this TADF guest, so that more triplet excitons are harvested for light emission. The sky‐blue TADF electroluminescence with this host/guest pair gave a record‐high external quantum efficiency of 24.1 % at maximum and 22.8 % at 500 cd m?2. 相似文献
7.
Polyblend and nanocomposite films of sodium salt of carboxymethylcellulose (Na‐CMC)/polyacrylamide (PAM) and Na‐CMC/PAM modified with carbon nanotubes (CNT) were synthesized by the solution casting technique. The effect of PAM and CNT loading on the structural, optical, and nanoscale free volume properties of Na‐CMC was studied. X‐ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy exhibited the existence of strong interactions between Na‐CMC and PAM and the non‐destructive effect of CNT on Na‐CMC/PAM structure. The HR‐TEM revealed the multi‐walled structure of CNT with a 7.06‐nm wall thickness and a 6.92‐nm wall inner diameter. Positron annihilation lifetime spectroscopy (PALS) was done, in a vacuum and at 30°C to 200°C, to investigate the nanoscale free volume properties by using a conventional fast‐fast coincidence spectrometer. It was found that the o‐Ps lifetime (τ3 ) and free volume (Vh) increase with increasing CNT percentage in the Na‐CMC/PAM blend. The distribution of the o‐Ps lifetime was broadened with increasing CNT ratios. Furthermore, the glass transition temperature (Tg) increases with increasing loads of CNT. For the first time, a correlation was done between Urbach energy (EU) and Vh. Finally, the results were represented and discussed in the frame of free volume properties. Optical measurements showed that the transmittance T% of Na‐CMC/PAM was 91.12% and decreased to 68.42% and 36.45% after loading with 1.0 and 2.0 wt % CNT. In addition, the blend shows higher insulating properties compared with the individual polymers. The CNT incorporation reduces the band gap significantly and increases the EU in the films. 相似文献
8.
Synthesis and Fluorescence Properties of Pyrimidine‐Based Diboron Complexes with Donor–π–Acceptor Structures
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Dr. Yasuhiro Kubota Kouhei Kasatani Takahiro Niwa Dr. Hiroyasu Sato Prof. Dr. Kazumasa Funabiki Prof. Dr. Masaki Matsui 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(5):1816-1824
Pyrimidine‐based diboron complexes bearing β‐iminoenolate ligands and phenyl groups as bulky substituents on the boron atoms were synthesized as novel fluorescent dyes, and their fluorescence properties were investigated in solution and in the solid state. The diboron complexes with donor–π–acceptor structures showed positive solvatochromism in the fluorescence spectra. The cyano derivative exhibited the most dramatic redshift of the fluorescence maximum Fmax with increasing solvent polarity (from 551 nm in n‐hexane to 710 nm in acetonitrile). The diboron complexes showed solid‐state fluorescence in the range of 578–706 nm with fluorescence quantum yields of 0.06–0.28. Additionally, the trifluoromethyl derivative exhibited solvent‐inclusion solid‐state fluorescence. The trifluoromethyl derivative formed toluene‐inclusion and ethyl acetate‐inclusion crystals. The toluene‐inclusion crystal (Fmax=668 nm, Φf=0.16) showed a blueshifted Fmax and higher Φf value compared to the original trifluoromethyl derivative (Fmax=694 nm, Φf=0.08) in the solid state. On the other hand, the Fmax (709 nm) and Φf (0.04) values of the ethyl acetate‐inclusion crystal were redshifted and lower, respectively. 相似文献
9.
Gregor S. Pilzak Kitty van Gruijthuijsen Reindert H. van Doorn Barend van Lagen Ernst J. R. Sudhölter Prof. Dr. Han Zuilhof Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(36):9085-9096
Novel and highly soluble hybrid conjugated organic oligomers consisting of oligodiacetylene and thiophene units have been synthesized in high purity through iterative and divergent approaches based on a sequence of Sonogashira reactions. The series of thiophene‐containing oligodiacetylenes (ThODAs) and homocoupled ThODAs (HThODAs) show—both in solution and in the solid state—a strong optical absorption, which is progressively red shifted with increasing chain length. The linear correlation of the absorption maximum (λAmax) with the inverse of conjugation length (CL=number of double and triple bonds) shows that the effective conjugation length of this system is extended up to at least CL=20. Furthermore, absorption measurements of dropcast thin films display not only a bathochromic shift of the absorption maxima but also a higher wavelength absorption, which is attributed to increased π–π interactions. The wavelength of the maximum fluorescence emission (λEmax) also increases with CL, and emission is maximal for oligomers with CL=7–12 (fluorescence quantum yield ΦF=~0.2). Both longer and shorter oligomers display marginal emission. The calculated Stokes shifts of these planar materials are relatively large (0.4 eV) for all oligomers, and likely due to excitation to the S2 state, thus suggesting that the presence of enyne moieties dominates the ordering of the lowest excited states. The fluorescence lifetimes (τF) are short (τF,max=?1 ns) and closely follow the tendency obtained for the fluorescence quantum yield. The anisotropy lifetimes show a near‐linear increase with CL, in line with highly rigid oligomers. 相似文献
10.
Alena A. Volgusheva Daria A. Todorenko Ivan V. Konyukhov Elena N. Voronova Sergey I. Pogosyan Tatyana Yu Plyusnina Sergey S. Khruschev Taras K. Antal 《Photochemistry and photobiology》2023,99(4):1106-1114
The effect of the toxicant 2,3′,4,4′,6-pentachlorobiphenyl (PCB-119) on the growth, chlorophyll content, and PSII activity of C. sorokiniana cells was investigated. A strong negative effect of the toxicant was observed at PCB concentration of 0.05 μg mL−1, when culture growth ceased, chlorophyll strongly bleached, and cell death occurred. The use of original highly sensitive fluorimeter to measure three types of high-resolution chlorophyll fluorescence kinetics allowed us to detect an initial dramatic decrease in the activity of primary photosynthetic reactions, followed by their almost complete recovery at the end of the incubation period when most cells were dead. The study of the distribution of individual cells in culture in terms of Fv/Fm parameter, which reflects the quantum yield of PSII photochemistry, revealed the existence of 2–3% of cells retaining high Fv/Fm (>0.7) in the presence of the toxicant. The treated cultures were able to resume growth after prolonged incubation in fresh medium. The high sensitivity fluorescence methods used made it possible to identify stress-resistant cells which maintain high photosynthetic activity in the presence of lethal doses of toxic substances; these cells provide recovery of the population after stress. 相似文献
11.
Rui‐Yan Li Bing‐Qiang Wang Zhi‐Ru Li Di Wu Ying Li 《International journal of quantum chemistry》2008,108(1):151-160
Using the counterpoise‐corrected potential energy surface method, the stationary structures of the π Br‐bond complexes C2H4‐nFn? BrF (n = 0–2) with all real frequencies have been obtained at MP2/aug‐cc‐pVDZ level. The order of the π Br‐bond length is 2.625 Å (C2H4? BrF) < 2.714 Å (C2H3F? BrF) < 2.751 Å (g‐C2H2F2? BrF) < 2.771 Å (trans‐C2H2F2? BrF) < 2.778 Å (cis‐C2H2F2? BrF). The interaction energies (Eint) are, respectively,‐5.9 (C2H4? BrF),‐4.4 (C2H3F? BrF),‐3.7 (g‐C2H2F2? BrF),‐3.1 (cis‐C2H2F2? BrF),‐2.8 kcal/mol (trans‐C2H2F2? BrF), at the CCSD (T)/aug‐cc‐pVDZ level, which include larger electron correlation contributions (Ecorre). The order of Ecorre is‐3.40 (C2H4? BrF),‐3.60 (C2H3F? BrF),‐3.85 (g‐C2H2F2? BrF),‐3.86 (cis‐C2H2F2? BrF),‐3.88 kcal/mol (trans‐C2H2F2? BrF). The earlier results show above that the F substituent effect elongates the π Br‐bond, reduces the Eint, and increases the Ecorre contribution of the interaction energy. Interestingly, the interaction energy of the cis‐C2H2F2? BrF structure with longer interaction distance is larger than that of the corresponding trans‐C2H2F2? BrF structure with shorter interaction distance. This reason comes from a special secondary interaction between lone pairs of Br atom with positive charge and some atoms (H, C) with positive charges of C2H2F2 in the cis‐C2H2F2? BrF structure. Comparing with corresponding C2H4‐nFn? ClF and C2H4‐nFn? HF, the C2H4‐nFn? BrF system has the larger Eint in which main contribution comes from the larger Ecorre, representing the larger dispersion interaction. The larger Ecorre contribution of the Eint of π Br‐bond can be used to understand that the π Br‐bond is shorter and stronger than corresponding π Cl‐bond. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 相似文献
12.
Prof. Dr. Masaki Shimizu Dr. Youhei Takeda Masahiro Higashi Prof. Dr. Tamejiro Hiyama 《化学:亚洲杂志》2011,6(9):2536-2544
Dimethoxybis(3,3,3‐trifluo‐ropropen‐1‐yl)benzenes were prepared through palladium‐catalyzed double cross‐coupling reactions of diiododimethoxybenzenes with CF3C≡CZnCl, followed by reduction of CF3C≡C groups with LiAlH4 or H2 in the presence of the Lindlar catalyst. The edges of the absorption spectra of 1,2‐(MeO)2‐4,5‐(CF3CHC=CH)2benzenes 1 and 1,3‐(MeO)2‐4,6‐(CF3CH=CH)2benzenes 2 in cyclohexane ranged from 348 to 360 nm, whereas the absorption spectra of 1,4‐(MeO)2‐2,5‐[(E)‐CF3CH=CH]2 benzene ((E)‐ 3 ) ended at 406 nm. These findings indicate that the effective conjugation length of (E)‐ 3 was significantly larger than those of 1 and 2 . Consistently, 1 and 2 in cyclohexane exhibited fluorescence with emission maxima in the UV region, whereas (E)‐ 3 in cyclohexane emitted violet light with an emission maximum at 407 nm. All the fluorescence spectra of 1 – 3 in various solvents redshifted as the solvent polarity increased. The photoluminescence of 1 , E‐1 , Z‐1 , 2 , E‐2 , E‐2H , Z‐2 , E‐3 , E‐3H , Z‐3 in the solid states was also observed with emission maxima in the violet region. It is important to note that the quantum yields of (E)‐ 3 in a neat thin film and in a doped polymer film were 0.37 and 0.49, respectively. Density functional theory calculations suggested that the fluorine atoms contribute to a slight extension of both the HOMOs and the LUMOs, as well as narrowing of the HOMO–LUMO gaps when compared with the corresponding fluorine‐free analogues. In the case of (E)‐ 3 , it is suggested that the HOMO–LUMO transition includes charge transfer from the ethereal oxygen atoms to the C(sp2) CF3 moieties. 相似文献
13.
《Acta Crystallographica. Section C, Structural Chemistry》2018,74(10):1171-1179
3,5‐Bis(arylidene)‐4‐piperidone (BAP) derivatives display good antitumour and anti‐inflammatory activities because of their double α,β‐unsaturated ketone structural characteristics. If N‐benzenesulfonyl substituents are introduced into BAPs, the configuration of the BAPs would change significantly and their anti‐inflammatory activities should improve. Four N‐benzenesulfonyl BAPs, namely (3E,5E)‐1‐(4‐methylbenzenesulfonyl)‐3,5‐bis[4‐(trifluoromethyl)benzylidene]piperidin‐4‐one dichloromethane monosolvate, C28H21F6NO3S·CH2Cl2, ( 4 ), (3E,5E)‐1‐(4‐fluorobenzenesulfonyl)‐3,5‐bis[4‐(trifluoromethyl)benzylidene]piperidin‐4‐one, C27H18F7NO3S, ( 5 ), (3E,5E)‐1‐(4‐nitrobenzenesulfonyl)‐3,5‐bis[4‐(trifluoromethyl)benzylidene]piperidin‐4‐one, C27H18F6N2O5S, ( 6 ), and (3E,5E)‐1‐(4‐cyanobenzenesulfonyl)‐3,5‐bis[4‐(trifluoromethyl)benzylidene]piperidin‐4‐one dichloromethane monosolvate, C28H18F6N2O3S·CH2Cl2, ( 7 ), were prepared by Claisen–Schmidt condensation and N‐sulfonylation. They were characterized by NMR, FT–IR and HRMS (high resolution mass spectrometry). Single‐crystal structure analysis reveals that the two 4‐(trifluoromethyl)phenyl rings on both sides of the piperidone ring in ( 4 )–( 7 ) adopt an E stereochemistry of the olefinic double bonds. Molecules of both ( 4 ) and ( 6 ) are connected by hydrogen bonds into one‐dimensional chains. In ( 5 ) and ( 7 ), pairs of adjacent molecules embrace through intermolecular hydrogen bonds to form a bimolecular combination, which are further extended into a two‐dimensional sheet. The anti‐inflammatory activity data reveal that ( 4 )–( 7 ) significantly inhibit LPS‐induced interleukin (IL‐6) and tumour necrosis factor (TNF‐α) secretion. Most importantly, ( 6 ) and ( 7 ), with strong electron‐withdrawing substituents, display more potential inhibitory effects than ( 4 ) and ( 5 ). 相似文献
14.
Ruchi Singh Jishnu Naskar Uday V. Pathre Pramod A. Shirke 《Photochemistry and photobiology》2014,90(3):544-551
The response and the functioning of the photosynthetic machinery of cotton, Gossypium hirsutum during water stress was studied by leaf optical properties, linear (ETRII) and cyclic electron flow (CEF) and chlorophyll a fluorescence. We observed that in G. hirsutum, during water limitation, Chlorophyll b showed the best correlation with reflectance at 731 nm and is a better indicator of drought. Fv/Fm was observed to be very insensitive to mild water stress. However, during severe water stress the leaves exhibit considerable inhibition in Fv/Fm and an increase in anthocyanin levels by about 20‐fold. CEF was very responsive to mild water stress. The mild drought stress caused large decrease in the ability of the leaves to utilize the light energy. Photosystem I and photosystem II is protected from photoinhibition by high CEF and nonphotochemical quenching under mild water stress. While during severe drought stress, linear electron flow showed a sharp decrease in comparison to CEF. CEF play a major role in G. hirsutum leaves during mild as well as under severe water stress condition and is thus a good indicator of water stress. 相似文献
15.
Qian Xia Jinglu Tan Shengyang Cheng Yongnian Jiang Ya Guo 《Photochemistry and photobiology》2019,95(6):1495-1503
Following a step excitation, chlorophyll fluorescence (ChlF) from photosystem II (PSII) of a dark‐adapted photosynthetic organism exhibits the well‐known OJIP pattern. The OJIP induction has been widely used in plant science and agriculture engineering. While the J and I phases are related to transitions of photochemical reaction redox states, characteristic fluorescence intensities at the two phases (Fj and Fi) are often treated at fixed time points in routine measurement and thus do not account for variations in plant and experimental conditions, this (1) neglects the differences in the time of appearance of these phases, which is potentially useful information for characterizing plant status and environmental factors, and (2) leads to errors in measured Fj and Fi values in the many publications. In this work, an alternative method for consistent measurement of Fj and Fi was presented. The proposed method measures the curvatures in the OJIP curve and automatically tracks the characteristic transition points under variable sample and experimental conditions. Experiments were carried out to demonstrate the concept and classification capabilities of the method. This research has established a new framework to analyze ChlF and has enhanced the application capability of ChlF. It is expect useful in analysis ChlF from PSII. 相似文献
16.
Thermally activated delayed fluorescence (TADF)‐based organic light‐emitting diodes (OLEDs) have attracted enormous attention recently due to their capability to replace conventional phosphorescent organic light‐emitting diodes for practical applications. In this work, a newly designed CN‐substituted imidazopyrazine moiety was utilized as an electron‐accepting unit in a TADF emitter. Two TADF emitters, 8‐(3‐cyano‐4‐(9,9‐dimethylacridin‐10(9H)‐yl)phenyl)‐2‐phenylimidazo[1,2‐a]pyrazine‐3‐carbonitrile (Ac‐CNImPyr) and 8‐(3‐cyano‐4‐(10H‐phenoxazin‐10‐yl)phenyl)‐2‐phenylimidazo[1,2‐a]pyrazine‐3‐carbonitrile (PXZ‐CNImPyr), were developed based on the CN‐substituted imidazopyrazine acceptor combined with acridine and phenoxazine donor, respectively. A CN‐substituted phenyl spacer was introduced between the donor and acceptor for a sufficiently small singlet‐triplet energy gap (ΔEST) and molecular orbital management. Small ΔEST of 0.07 eV was achieved for the phenoxazine donor‐based PXZ‐CNImPyr emitter. As a result, an organic light‐emitting diode based on the PXZ‐CNImPyr emitter exhibited a high external quantum efficiency of up to 12.7 %, which surpassed the EQE limit of common fluorescent emitters. Hence, the CN‐modified imidazopyrazine unit can be introduced as a new acceptor for further modifications to develop efficient TADF‐based OLEDs. 相似文献
17.
Dunaliella tertiolecta (Chlorophyta) Avoids Cell Death Under Ultraviolet Radiation By Triggering Alternative Photoprotective Mechanisms
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María Segovia Teresa Mata Armando Palma Candela García‐Gómez Rosario Lorenzo Alicia Rivera Félix L. Figueroa 《Photochemistry and photobiology》2015,91(6):1389-1402
The effect of different ultraviolet radiation (UVR) treatments combining PAR (P), UVA (A) and UVB (B) on the molecular physiology of Dunaliella tertiolecta was studied during 6 days to assess the response to chronic UVR exposure. UVR reduced cell growth but did not cause cell death, as shown by the absence of SYTOX Green labeling and cellular morphology. However, caspase‐like enzymatic activities (CLs), (regarded as cell death proteases), were active even though the cells were not dying. Maximal quantum yield of fluorescence (Fv/Fm) and photosynthetic electron transport rate (ETR) dropped. Decreased nonphotochemical quenching (NPQ) paralleled a drop in xanthophyll cycle de‐epoxidation under UVB. Reactive oxygen species (ROS) and D1 protein accumulation were inversely correlated. PAB exhibited elevated ROS production at earlier times. Once ROS decayed, D1 protein recovered two‐fold compared with P and PA at later stages. Therefore, PsbA gene was still transcribed, suggesting ROS involvement in D1 recovery by its direct effect on mRNA‐translation. We add evidence of an UVB‐induced positive effect on the cells when P is present, providing photoprotection and resilience, by means of D1 repair. This allowed cells to survive. The photoprotective mechanisms described here (which are counterintuitive in principle) conform to an important ecophysiological response regarding light stress acclimation. 相似文献
18.
Masaki Shimizu Prof. Dr. Hironori Tatsumi Kenji Mochida Katsuhiro Shimono Dr. Tamejiro Hiyama Prof. Dr. 《化学:亚洲杂志》2009,4(8):1289-1297
Double Horner–Wadsworth–Emmons reaction of (E)‐2,3‐diaryl‐1,4‐bis(diethylphosphonyl)but‐2‐ene with (p‐substituted) benzaldehydes gave (1E,3E,5E)‐1,3,4,6‐tetraarylhexa‐1,3,5‐trienes in moderate to good yields. Substitution of electron‐withdrawing or ‐donating groups at the para position of the 1,6‐diphenyl groups induced a slight bathochromic shift of UV spectra measured in CHCl3 compared with that of the parent 1,3,4,6‐tetraphenylhexa‐1,3,5‐triene. Although fluorescence was not observed with all the trienes in CHCl3, they markedly emitted visible light in powder forms with quantum yields of 0.15–0.44. Introduction of amino groups at the para position of the 3,4‐diphenyl groups induced a bathochromic shift of emission maxima with good solid‐state quantum yields. Thus, the tetraarylated triene framework is found to serve as a new class of fluorophores that exhibit aggregation‐induced emission. 相似文献
19.
Stress Tolerance of the Endemic Antarctic Brown Alga Desmarestia anceps to UV Radiation and Temperature is Mediated by High Concentrations of Phlorotannins
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María Rosa Flores‐Molina Ralf Rautenberger Pamela Muñoz Pirjo Huovinen Iván Gómez 《Photochemistry and photobiology》2016,92(3):455-466
The endemic Antarctic brown macroalga Desmarestia anceps is strongly shade‐adapted, but shows also a high capacity to cope with different environmental stressors, e.g. UV radiation and temperature. Therefore, this species colonizes wide depth gradients, which are characterized by changing environmental conditions. In this study, we examine whether the different physiological abilities allowing D. anceps to grow across a wide depth range is determined by high levels of phlorotannins. Photosynthesis, measured by PAM‐fluorometry, the contents of soluble phlorotannins, antioxidant capacities of field grown were analyzed in response to different conditions of radiation (PAR and PAR + UV) and temperature (2, 7 and 12°C). The results show that maximal quantum of fluorescence (Fv/Fm) decreased with increasing doses of UV radiation, but remained unaffected by temperature. High levels of soluble phlorotannins were detected and confirmed by microscopic observation revealing the abundance of large physodes. Exposure to UV radiation and elevated temperature showed that phlorotannins were not inducible by UV but increased at 12°C. ROS scavenging capacity was positively correlated with the contents of phlorotannins. In general, highest contents of phlorotannins were correlated with the lowest inhibition of Fv/Fm in all experimental treatments, highlighting the UV‐protective role of these compounds in D. anceps. 相似文献
20.
A competitive indirect fluoroimmunoassay of free estradiol (E2) was established based on the thermal sensitivity of hydrogel–‐poly‐N‐isopropylacrylamide. Free estradiol was covalently bound to bovine serum albumin (BSA) to form complete antigen (E2‐BSA), which was in turn labeled by fluorescein isothiocyanate (FTTC) as the fluorescence probe. The anti‐ E2 monoclonal antibody (McAb) was prepared by an in vivo method, and coupled with N‐isopropylacrylamide (NIPA) to make an immune copolymer, poly‐N‐isopropylacylamidemonoclonal antibody (pNIPA‐McAb), for the determination of free E2. The immunoassay method was based on the competitive binding of free E2 and fluoresceinated antigen (E2‐BSA‐FTTC) with limited amount of pNIPA‐McAb. When the immunological reaction was over, precipitation and centrifugal procedures were carried out to separate pNIPA‐McAb‐E2‐BSA‐FTTC from other constituents in solution. The precipitate pNIPA‐McAb‐E2‐BSA‐FTTC was dissolved in solution and then the fluorescence intensity was measured. The calibration curve covered a range of 78–500 ng/mL for free E2. The recoveries were 91.2–107.2%. 相似文献