photoprotection Dotaz Zobrazit nápovědu
Despite the health benefits of the sun, overexposure to solar radiation without proper precautions can cause irreversible damage to exposed skin. In the search for balance between the risks and benefits of exposure to solar radiation in human health, a technological alternative was found, the incorporation of photoprotective products in lipid nanoparticulate systems for topical application. These nanometric systems have demonstrated several advantages when used as adjuvants in photoprotection compared to chemical and/or physical sunscreens alone. The increase in the sun protection factor (SPF), photostability and UV action spectrum are parameters that have benefited from the application of these systems in order to increase the effectiveness and safety of photoprotective formulations containing organic and/or inorganic sunscreens.
- Klíčová slova
- lipid nanofilms, solar photoprotection, sun exposure, ultraviolet radiation,
- Publikační typ
- časopisecké články MeSH
- přehledy MeSH
One-helix proteins 1 and 2 (OHP1/2) are members of the family of light-harvesting-like proteins (LIL) in plants, and their potential function(s) have been initially analyzed only recently. OHP1 and OHP2 are structurally related to the transmembrane α-helices 1 and 3 of all members of the light-harvesting complex (LHC) superfamily. Arabidopsis thaliana OHPs form heterodimers which bind 6 chlorophylls (Chls) a and two carotenoids in vitro. Their function remains unclear, and therefore, a spectroscopic study with reconstituted OHP1/OHP2-complexes was performed. Steady-state spectroscopy did not indicate singlet excitation energy transfer between pigments. Thus, a light-harvesting function can be excluded. Possible pigment-storage and/or -delivery functions of OHPs require photoprotection of the bound Chls. Hence, Chl and carotenoid triplet formation and decays in reconstituted OHP1/2 dimers were measured using nanosecond transient absorption spectroscopy. Unlike in all other photosynthetic LHCs, unquenched Chl triplets were observed with unusually long lifetimes. Moreover, there were virtually no differences in both Chl and carotenoid triplet state lifetimes under either aerobic or anaerobic conditions. The results indicate that both Chls and carotenoids are shielded by the proteins from interactions with ambient oxygen and, thus, protected against formation of singlet oxygen. Only a minor portion of the Chl triplets was quenched by carotenoids. These results are in stark contrast to all previously observed photoprotective processes in LHC/LIL proteins and, thus, may constitute a novel mechanism of photoprotection in the plant photosynthetic apparatus.
- MeSH
- Arabidopsis chemie MeSH
- chlorofyl chemie MeSH
- fotochemické procesy MeSH
- fotosyntéza MeSH
- karotenoidy chemie MeSH
- kinetika MeSH
- konformace proteinů MeSH
- kyslík chemie MeSH
- multimerizace proteinu MeSH
- přenos energie MeSH
- proteiny huseníčku chemie MeSH
- proteiny vázající chlorofyl chemie MeSH
- světlosběrné proteinové komplexy chemie MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- chlorofyl MeSH
- karotenoidy MeSH
- kyslík MeSH
- OHP1 protein, Arabidopsis MeSH Prohlížeč
- Ohp2 protein, Arabidopsis MeSH Prohlížeč
- proteiny huseníčku MeSH
- proteiny vázající chlorofyl MeSH
- světlosběrné proteinové komplexy MeSH
We assessed the photosynthetic responses of eight wheat varieties in conditions of a simulated heat wave in a transparent plastic tunnel for one week. We found that high temperatures (up to 38 °C at midday and above 20 °C at night) had a negative effect on the photosynthetic functions of the plants and provided differentiation of genotypes through sensitivity to heat. Measurements of gas exchange showed that the simulated heat wave led to a 40% decrease in photosynthetic activity on average in comparison to the control, with an unequal recovery of individual genotypes after a release from stress. Our results indicate that the ability to recover after heat stress was associated with an efficient regulation of linear electron transport and the prevention of over-reduction in the acceptor side of photosystem I.
- Klíčová slova
- heat stress, high temperatures, photoinhibition, photoprotection, photosynthesis, photosystem I, wheat,
- Publikační typ
- časopisecké články MeSH
Photoprotection is fundamental in photosynthesis to avoid oxidative photodamage upon excess light exposure. Excited chlorophylls (Chl) are quenched by carotenoids, but the precise molecular origin remains controversial. The cyanobacterial HliC protein belongs to the Hlip family ancestral to plant light-harvesting complexes, and binds Chl a and β-carotene in 2:1 ratio. We analyzed HliC by watermarked femtosecond stimulated Raman spectroscopy to follow the time evolution of its vibrational modes. We observed a 2 ps rise of the C═C stretch band of the 2Ag- (S1) state of β-carotene upon Chl a excitation, demonstrating energy transfer quenching and fast excess-energy dissipation. We detected two distinct β-carotene conformers by the C═C stretch frequency of the 2Ag- (S1) state, but only the β-carotene whose 2Ag- energy level is significantly lowered and has a lower C═C stretch frequency is involved in quenching. It implies that the low carotenoid S1 energy that results from specific pigment-protein or pigment-pigment interactions is the key property for creating a dissipative energy channel. We conclude that watermarked femtosecond stimulated Raman spectroscopy constitutes a promising experimental method to assess energy transfer and quenching mechanisms in oxygenic photosynthesis.
- Publikační typ
- časopisecké články MeSH
Xanthophylls in light harvesting complexes perform a number of functions ranging from structural support to light-harvesting and photoprotection. In the major light harvesting complex of photosystem II in plants (LHCII), the innermost xanthophyll binding pockets are occupied by lutein molecules. The conservation of these sites within the LHC protein family suggests their importance in LHCII functionality. In the present work, we induced the photoprotective switch in LHCII isolated from the Arabidopsis mutant npq1lut2, where the lutein molecules are exchanged with violaxanthin. Despite the differences in the energetics of the pigments and the impairment of chlorophyll fluorescence quenching in vivo, we show that isolated complexes containing violaxanthin are still able to induce the quenching switch to a similar extent to wild type LHCII monomers. Moreover, the same spectroscopic changes take place, which suggest the involvement of the terminal emitter site (L1) in energy dissipation in both complexes. These results indicate the robust nature of the L1 xanthophyll binding domain in LHCII, where protein structural cues are the major determinant of the function of the bound carotenoid.
- MeSH
- Arabidopsis chemie MeSH
- fotochemické procesy MeSH
- fotosystém II - proteinový komplex chemie metabolismus MeSH
- lutein chemie metabolismus MeSH
- xanthofyly chemie metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- fotosystém II - proteinový komplex MeSH
- lutein MeSH
- xanthofyly MeSH
Plants collect light for photosynthesis using light-harvesting complexes (LHCs)-an array of chlorophyll proteins that are able to reversibly switch from harvesting to energy-dissipation mode to prevent damage of the photosynthetic apparatus. LHC antennae as well as other members of the LHC superfamily evolved from cyanobacterial ancestors called high light-inducible proteins (Hlips). Here, we characterized a purified Hlip family member HliD isolated from the cyanobacterium Synechocystis sp. PCC 6803. We found that the HliD binds chlorophyll-a (Chl-a) and β-carotene and exhibits an energy-dissipative conformation. Using femtosecond spectroscopy, we demonstrated that the energy dissipation is achieved via direct energy transfer from a Chl-a Qy state to the β-carotene S1 state. We did not detect any cation of β-carotene that would accompany Chl-a quenching. These results provide proof of principle that this quenching mechanism operates in the LHC superfamily and also shed light on the photoprotective role of Hlips and the evolution of LHC antennae.
- MeSH
- beta-karoten chemie MeSH
- chlorofyl a MeSH
- chlorofyl chemie MeSH
- elektrony MeSH
- fluorescenční spektrometrie MeSH
- fotochemické procesy * MeSH
- fotosyntéza MeSH
- karotenoidy chemie MeSH
- konformace proteinů MeSH
- přenos energie MeSH
- rostlinné proteiny chemie MeSH
- rostliny metabolismus MeSH
- sinice metabolismus MeSH
- spektrofotometrie MeSH
- světlo MeSH
- světlosběrné proteinové komplexy metabolismus MeSH
- Synechocystis metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- alpha-carotene MeSH Prohlížeč
- beta-karoten MeSH
- chlorofyl a MeSH
- chlorofyl MeSH
- karotenoidy MeSH
- rostlinné proteiny MeSH
- světlosběrné proteinové komplexy MeSH
Plants are increasingly exposed to events of elevated temperature and water deficit, which threaten crop productivity. Understanding the ability to rapidly recover from abiotic stress, restoring carbon assimilation and biomass production, is important to unravel crop climate resilience. This study compared the photosynthetic performance of two Triticum aestivum L. cultivars, Sokoll and Paragon, adapted to the climate of Mexico and UK, respectively, exposed to 1-week water deficit and high temperatures, in isolation or combination. Measurements included photosynthetic assimilation rate, stomatal conductance, in vitro activities of Rubisco (EC 4.1.1.39) and invertase (INV, EC 3.2.1.26), antioxidant capacity and chlorophyll a fluorescence. In both genotypes, under elevated temperatures and water deficit (WD38°C), the photosynthetic limitations were mainly due to stomatal restrictions and to a decrease in the electron transport rate. Chlorophyll a fluorescence parameters clearly indicate differences between the two genotypes in the photoprotection when subjected to WD38°C and showed faster recovery of Paragon after stress relief. The activity of the cytosolic invertase (CytINV) under these stress conditions was strongly related to the fast photosynthesis recovery of Paragon. Taken together, the results suggest that optimal sucrose export/utilization and increased photoprotection of the electron transport machinery are important components to limit yield fluctuations due to water shortage and elevated temperatures.
The Arabidopsis vte1 mutant is devoid of tocopherol and plastochromanol (PC-8). When exposed to excess light energy, vte1 produced more singlet oxygen (1 O2 ) and suffered from extensive oxidative damage compared with the wild type. Here, we show that overexpressing the solanesyl diphosphate synthase 1 (SPS1) gene in vte1 induced a marked accumulation of total plastoquinone (PQ-9) and rendered the vte1 SPS1oex plants tolerant to photooxidative stress, indicating that PQ-9 can replace tocopherol and PC-8 in photoprotection. High total PQ-9 levels were associated with a noticeable decrease in 1 O2 production and higher levels of Hydroxyplastoquinone (PQ-C), a 1 O2 -specific PQ-9 oxidation product. The extra PQ-9 molecules in the vte1 SPS1oex plants were stored in the plastoglobules and the chloroplast envelopes, rather than in the thylakoid membranes, whereas PQ-C was found almost exclusively in the thylakoid membranes. Upon exposure of wild-type plants to high light, the thylakoid PQ-9 pool decreased, whereas the extrathylakoid pool remained unchanged. In vte1 and vte1 SPS1oex plants, the PQ-9 losses in high light were strongly amplified, affecting also the extrathylakoid pool, and PQ-C was found in high amounts in the thylakoids. We conclude that the thylakoid PQ-9 pool acts as a 1 O2 scavenger and is replenished from the extrathylakoid stock.
- Klíčová slova
- antioxidant, reactive oxygen species, tocopherol,
- MeSH
- alkyltransferasy a aryltransferasy metabolismus MeSH
- chlorofyl metabolismus MeSH
- chloroplasty metabolismus MeSH
- elektronová paramagnetická rezonance MeSH
- oxidační stres účinky záření MeSH
- peroxidace lipidů MeSH
- plastochinon metabolismus MeSH
- proteiny huseníčku metabolismus MeSH
- scavengery volných radikálů metabolismus MeSH
- singletový kyslík metabolismus MeSH
- světlo MeSH
- tylakoidy metabolismus MeSH
- vysokoúčinná kapalinová chromatografie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- alkyltransferasy a aryltransferasy MeSH
- chlorofyl MeSH
- plastochinon MeSH
- proteiny huseníčku MeSH
- scavengery volných radikálů MeSH
- singletový kyslík MeSH
- SPS1 protein, Arabidopsis MeSH Prohlížeč
Carotenoids are known to offer protection against the potentially damaging combination of light and oxygen encountered by purple phototrophic bacteria, but the efficiency of such protection depends on the type of carotenoid. Rhodobacter sphaeroides synthesizes spheroidene as the main carotenoid under anaerobic conditions whereas, in the presence of oxygen, the enzyme spheroidene monooxygenase catalyses the incorporation of a keto group forming spheroidenone. We performed ultrafast transient absorption spectroscopy on membranes containing reaction center-light-harvesting 1-PufX (RC-LH1-PufX) complexes and showed that when oxygen is present the incorporation of the keto group into spheroidene, forming spheroidenone, reconfigures the energy transfer pathway in the LH1, but not the LH2, antenna. The spheroidene/spheroidenone transition acts as a molecular switch that is suggested to twist spheroidenone into an s-trans configuration increasing its conjugation length and lowering the energy of the lowest triplet state so it can act as an effective quencher of singlet oxygen. The other consequence of converting carotenoids in RC-LH1-PufX complexes is that S(2)/S(1)/triplet pathways for spheroidene is replaced with a new pathway for spheroidenone involving an activated intramolecular charge-transfer (ICT) state. This strategy for RC-LH1-PufX-spheroidenone complexes maintains the light-harvesting cross-section of the antenna by opening an active, ultrafast S(1)/ICT channel for energy transfer to LH1 Bchls while optimizing the triplet energy for singlet oxygen quenching. We propose that spheroidene/spheroidenone switching represents a simple and effective photoprotective mechanism of likely importance for phototrophic bacteria that encounter light and oxygen.
- MeSH
- bakteriální proteiny chemie metabolismus MeSH
- bakteriochlorofyly chemie metabolismus MeSH
- buněčná membrána metabolismus MeSH
- karotenoidy chemie metabolismus MeSH
- kyslík metabolismus MeSH
- molekulární struktura MeSH
- přenos energie účinky záření MeSH
- Proteobacteria chemie metabolismus MeSH
- Rhodobacter sphaeroides chemie metabolismus MeSH
- spektrofotometrie MeSH
- světlo MeSH
- světlosběrné proteinové komplexy chemie metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Research Support, U.S. Gov't, Non-P.H.S. MeSH
- Názvy látek
- bakteriální proteiny MeSH
- bakteriochlorofyly MeSH
- karotenoidy MeSH
- kyslík MeSH
- PufX protein, Rhodobacter MeSH Prohlížeč
- spheroidene MeSH Prohlížeč
- spheroidenone MeSH Prohlížeč
- světlosběrné proteinové komplexy MeSH
Solar radiation can cause damage to the skin, leading to various adverse effects such as sunburn, reactive oxygen species production, inflammation, DNA damage, and photoaging. To study the potential of photoprotective agents, full-thickness skin models are increasingly being used as in vitro tools. One promising approach to photoprotection involves targeting the redox-sensitive transcription factor Nrf2, which is responsible for regulating various cellular defense mechanisms, including the antioxidant response, inflammatory signaling, and DNA repair. Obacunone, a natural triterpenoid, has been identified as a potent Nrf2 agonist. The present study aims to evaluate the relevance of full-thickness (FT) skin models in photoprotection studies and to explore the potential photoprotective effects of obacunone on those models and in human keratinocytes. Phenion® full-thickness skin models and keratinocytes were incubated with increasing concentrations of obacunone and irradiated with solar-simulated radiation (SSR). Various photodamage markers were evaluated, including histological integrity, oxidative stress, apoptosis, inflammation, photoaging-related dermal markers, and photocarcinogenesis markers. Increasing doses of SSR were found to modulate various biomarkers related to sun damage in the FT skin models. However, obacunone attenuated cytotoxicity, inflammation, oxidative stress, sunburn reaction, photoaging, and photocarcinogenesis in both keratinocytes and full thickness skin models exposed to SSR. These results suggest that obacunone may have potential as a photoprotective agent for preventing the harmful effects of solar radiation on the skin.
- Klíčová slova
- full-thickness skin model, obacunone, photodamage, photoprotection,
- MeSH
- faktor 2 související s NF-E2 genetika MeSH
- keratinocyty MeSH
- kůže patologie MeSH
- lidé MeSH
- radioprotektivní látky * farmakologie MeSH
- sluneční spáleniny * MeSH
- ultrafialové záření škodlivé účinky MeSH
- zánět prevence a kontrola patologie MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- faktor 2 související s NF-E2 MeSH
- obacunone MeSH Prohlížeč
- radioprotektivní látky * MeSH
