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排序方式: 共有227条查询结果,搜索用时 31 毫秒
1.
Rudi Berera Ivo H.M. van Stokkum Sandrine d'Haene John T.M. Kennis Rienk van Grondelle Jan P. Dekker 《Biophysical journal》2009,96(6):2261-2267
When grown under a variety of stress conditions, cyanobacteria express the isiA gene, which encodes the IsiA pigment-protein complex. Overexpression of the isiA gene under iron-depletion stress conditions leads to the formation of large IsiA aggregates, which display remarkably short fluorescence lifetimes and thus a strong capacity to dissipate energy. In this work we investigate the underlying molecular mechanism responsible for chlorophyll fluorescence quenching. Femtosecond transient absorption spectroscopy allowed us to follow the process of energy dissipation in real time. The light energy harvested by chlorophyll pigments migrated within the system and eventually reaches a quenching site where the energy is transferred to a carotenoid-excited state, which dissipates it by decaying to the ground state. We compare these findings with those obtained for the main light-harvesting complex in green plants (light-harvesting complex II) and artificial light-harvesting antennas, and conclude that all of these systems show the same mechanism of energy dissipation, i.e., one or more carotenoids act as energy dissipators by accepting energy via low-lying singlet-excited S1 states and dissipating it as heat. 相似文献
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Mihai Bragaru C. P. van Wilgen Jan H. B. Geertzen Suzette G. J. B. Ruijs Pieter U. Dijkstra Rienk Dekker 《PloS one》2013,8(3)
Introduction
Although individuals with lower limb amputation may benefit from participation in sports, less than 40% do so.Aim
To identify the barriers and facilitators that influence participation in sports for individuals with lower limb amputation.Design
Qualitative study.Participants
Twenty six individuals with lower limb amputation, all originating from the Dutch provinces of Groningen and Drenthe, of which 13 athletes.Methods
Semi-structured interviews were used to gather information. Following thematic analysis, emerging themes were organized in three categories Technical, Social and Personal.Results
Sport was perceived as enjoyable activity that would help participants to become and stay healthy, improve the number of social contacts, reduce phantom pain and decrease daily tension. Inadequate facilities, problematic transportation, trivialization from others, poor health and lack of motivation or the lack of a sports partner were barriers commonly mentioned by non-athletes. Remarkably, while all athletes were successful prosthetic users, the majority chose to participate in sports for which prosthesis was neither required nor needed.Conclusions
Each individual with lower limb amputation needs to be counselled according to the barriers and facilitators he/she personally experiences. Athletes appeared to be more proactive in searching for a solution and also appeared less discouraged by failing. 相似文献4.
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Maxime T. A. Alexandre Kathi Gundermann Andrew A. Pascal Rienk van Grondelle Claudia Büchel Bruno Robert 《Photosynthesis research》2014,119(3):273-281
In this study, we demonstrate the selective in vivo detection of diadinoxanthin (DD) and diatoxanthin (DT) in intact Cyclotella cells using resonance Raman spectroscopy. In these cells, we were able to assess both the content of DD and DT carotenoids relative to chlorophyll and their conformation. In addition, the sensitivity and selectivity of the technique allow us to discriminate between different pools of DD on a structural basis, and to follow their fate as a function of the illumination conditions. We report that the additional DD observed when cells are grown in high-light conditions adopts a more twisted conformation than the lower levels of DD present when the cells are grown in low-light (LL) conditions. Thus, we conclude that this pool of DD is more tightly bound to a protein-binding site, which must differ from the one occupied by the DD present in LL conditions. 相似文献
7.
Wojciech Giera Sebastian Szewczyk Michael D. McConnell Joris Snellenburg Kevin E. Redding Rienk van Grondelle Krzysztof Gibasiewicz 《BBA》2014
Identical time-resolved fluorescence measurements with ~ 3.5-ps resolution were performed for three types of PSI preparations from the green alga, Chlamydomonas reinhardtii: isolated PSI cores, isolated PSI–LHCI complexes and PSI–LHCI complexes in whole living cells. Fluorescence decay in these types of PSI preparations has been previously investigated but never under the same experimental conditions. As a result we present consistent picture of excitation dynamics in algal PSI. Temporal evolution of fluorescence spectra can be generally described by three decay components with similar lifetimes in all samples (6–8 ps, 25–30 ps, 166–314 ps). In the PSI cores, the fluorescence decay is dominated by the two fastest components (~ 90%), which can be assigned to excitation energy trapping in the reaction center by reversible primary charge separation. Excitation dynamics in the PSI–LHCI preparations is more complex because of the energy transfer between the LHCI antenna system and the core. The average trapping time of excitations created in the well coupled LHCI antenna system is about 12–15 ps longer than excitations formed in the PSI core antenna. Excitation dynamics in PSI–LHCI complexes in whole living cells is very similar to that observed in isolated complexes. Our data support the view that chlorophylls responsible for the long-wavelength emission are located mostly in LHCI. We also compared in detail our results with the literature data obtained for plant PSI. 相似文献
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Huzifa M.A.M. Elnour Lars Dietzel Charusheela Ramanan Claudia Büchel Rienk van Grondelle Tjaart P.J. Krüger 《BBA》2018,1859(10):1151-1160
Transient absorption spectroscopy has been applied to investigate the energy dissipation mechanisms in the nonameric fucoxanthin-chlorophyll-a,c-binding protein FCPb of the centric diatom Cyclotella meneghiniana. FCPb complexes in their unquenched state were compared with those in two types of quenching environments, namely aggregation-induced quenching by detergent removal, and clustering via incorporation into liposomes. Applying global and target analysis, in combination with a fluorescence lifetime study and annihilation calculations, we were able to resolve two quenching channels in FCPb that involve chlorophyll-a pigments for FCPb exposed to both quenching environments. The fast quenching channel operates on a timescale of tens of picoseconds and exhibits similar spectral signatures as the unquenched state. The slower quenching channel operates on a timescale of tens to hundreds of picoseconds, depending on the degree of quenching, and is characterized by enhanced population of low-energy states between 680 and 710?nm. The results indicate that FCPb is, in principle, able to function as a dissipater of excess energy and can do this in vitro even more efficiently than the homologous FCPa complex, the sole complex involved in fast photoprotection in these organisms. This indicates that when a complex displays photoprotection-related spectral signatures in vitro it does not imply that the complex participates in photoprotection in vivo. We suggest that FCPa is favored over FCPb as the sole energy-regulating complex in diatoms because its composition can more easily establish the balance between light-harvesting and quenching required for efficient photoprotection. 相似文献
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