Structural Heterogeneity in DNA: Temperature Dependence of 2‐Aminopurine Fluorescence in Dinucleotides

Somsen, O. J. G.; Keukens, Linda B.; Keijzer, Merel; Hoek, A. van; Amerongen, Herbert van

doi:10.1002/cphc.200400648

Cited by 43 publications

(53 citation statements)

References 39 publications

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“…The various conformations may be reached because of excited-state dynamics rather than ground-state conformational sampling. This has been discussed before in the literature in dinucleotides of 2AP, 37,38 where the authors attributed some components of the multiexponential decay to excited-state dynamics rather than groundstate conformations.…”

Section: ' Conclusionmentioning

confidence: 91%

Pathways for Fluorescence Quenching in 2-Aminopurine π-Stacked with Pyrimidine Nucleobases

Liang

Matsika

2011

J. Am. Chem. Soc.

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Fluorescent analogues of nucleobases are very useful as probes to study DNA dynamics, because natural DNA does not fluoresce significantly. In many of these analogues, such as 2-aminopurine (2AP), the fluorescence is quenched when incorporated into DNA through processes that are not well understood. This work uses theoretical studies to examine fluorescence quenching pathways in 2AP-containing dimers. The singlet excited states of π-stacked dimer systems containing 2AP and a pyrimidine base, thymine or cytosine, have been studied using ab initio computational methods. Computed relaxation pathways along the excited-state surfaces reveal novel mechanisms that can lead to fluorescence quenching in the π-stacked dimers. The placement of 2AP on the 5' or 3' terminus of the dimers has different effects on the excitation energies and the relaxation pathways on the S(1) excited state. Conical intersections between the ground and first excited states exist when 2AP is placed at the 3' side, whereas the placement of 2AP at the 5' side leads to the switching of a bright state to a dark state. Both of these processes can lead to fluorescence quenching and may contribute to the fluorescence quenching observed in 2AP when incorporated in DNA.

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Section: ' Conclusionmentioning

confidence: 91%

Pathways for Fluorescence Quenching in 2-Aminopurine π-Stacked with Pyrimidine Nucleobases

Liang

Matsika

2011

J. Am. Chem. Soc.

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“…Time-resolved fluorescence. TCSPC measurements were performed with a home-built setup (54). Samples were excited with 400-and 465-nm pulses of 0.2 ps at repetition rate 3.8 MHz.…”

Section: Methodsmentioning

confidence: 99%

State transitions in Chlamydomonas reinhardtii strongly modulate the functional size of photosystem II but not of photosystem I

Ünlü¹,

Drop

Croce

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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137

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Plants and green algae optimize photosynthesis in changing light conditions by balancing the amount of light absorbed by photosystems I and II. These photosystems work in series to extract electrons from water and reduce NADP + to NADPH. Light-harvesting complexes (LHCs) are held responsible for maintaining the balance by moving from one photosystem to the other in a process called state transitions. In the green alga Chlamydomonas reinhardtii, a photosynthetic model organism, state transitions are thought to involve 80% of the LHCs. Here, we demonstrate with picosecond-fluorescence spectroscopy on C. reinhardtii cells that, although LHCs indeed detach from photosystem II in state 2 conditions, only a fraction attaches to photosystem I. The detached antenna complexes become protected against photodamage via shortening of the excited-state lifetime. It is discussed how the transition from state 1 to state 2 can protect C. reinhardtii in high-light conditions and how this differs from the situation in plants.time-resolved fluorescence spectroscopy | photoprotection O xygenic photosynthesis is the most important process for fueling life on earth. Light capture and subsequent charge separation processes occur in the so-called photosystems I and II (PSI and PSII). In plants and green algae, both PSs consist of a pigment-protein core complex surrounded by outer light-harvesting complexes (LHCs). Electronic excitations induced by the absorption of sunlight lead to charge separation in the reaction centers (RCs) of PSI and PSII, located in the cores of the PSs. These PSs work in series to extract electrons from water and reduce NADP + to NADPH. For optimal linear electron transport from water to NADP + , a balance is needed for the amount of light absorbed by the pigments in the two PSs.Besides carotenoids, the PSII core contains 35 chlorophylls a (Chls a), whereas this number is close to 100 for PSI (1). The outer LHCs consist of various components: The major lightharvesting complex LHCII (a trimer) harbors 12 carotenoids (Cars) and 42 chlorophylls (Chls), 24 of which are Chls a (2), the pigments that are largely responsible for excitation energy transfer (EET) to the PSII RC. In higher plants, there are also three monomeric minor LHCs per core, called CP24, CP26, and CP29, which show high sequence homology with LHCII (see, e.g., ref.3). In nonstressed conditions, between 85% and 90% of the excitations in PSII lead to charge separation in the RC (4). PSI in plants binds four LHCs (Lhca1-4) (5). The amount of LHCII in the plant membranes is variable and usually ranges from approximately two to approximately four trimers per PSII core, most of which are functionally connected to PSII, although part is also associated with PSI (6). In Chlamydomonas reinhardtii, PSI antenna size differs and there are nine Lhcas per PSI (7). Nine LhcbM genes, plus CP29 and CP26, codify for the antenna complexes of PSII (8), and it was recently shown that, in addition to CP26 and CP29, the PSII supercomplex contains three LHCII trimers per m...

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“…Time-correlated single photon counting was performed with a home-built setup, as described previously (34). In brief, the samples were diluted to an A 475 of 0.1 cm Ϫ1 and stirred in a 3.5-ml cuvette with a path length of 1 cm at 10°C.…”

Section: Methodsmentioning

confidence: 99%

Molecular Basis of Light Harvesting and Photoprotection in CP24

Passarini

Wientjes

Hienerwadel

et al. 2009

Journal of Biological Chemistry

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CP24 is a minor antenna complex of Photosystem II, which is specific for land plants. It has been proposed that this complex is involved in the process of excess energy dissipation, which protects plants from photodamage in high light conditions. Here, we have investigated the functional architecture of the complex, integrating mutation analysis with time-resolved spectroscopy. A comprehensive picture is obtained about the nature, the spectroscopic properties, and the role in the quenching in solution of the pigments in the individual binding sites. The lowest energy absorption band in the chlorophyll a region corresponds to chlorophylls 611/612, and it is not the site of quenching in CP24. Chlorophylls 613 and 614, which are present in the major lightharvesting complex of Photosystem appear to be absent in CP24. In contrast to all other light-harvesting complexes, CP24 is stable when the L1 carotenoid binding site is empty and upon mutations in the third helix, whereas mutations in the first helix strongly affect the folding/stability of the pigment-protein complex. The absence of lutein in L1 site does not have any effect on the quenching, whereas substitution of violaxanthin in the L2 site with lutein or zeaxanthin results in a complex with enhanced quenched fluorescence. Triplet-minus-singlet measurements indicate that zeaxanthin and lutein in site L2 are located closer to chlorophylls than violaxanthin, thus suggesting that they can act as direct quenchers via a strong interaction with a neighboring chlorophyll. The results provide the molecular basis for the zeaxanthin-dependent quenching in isolated CP24.

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Structural Heterogeneity in DNA: Temperature Dependence of 2‐Aminopurine Fluorescence in Dinucleotides

Cited by 43 publications

References 39 publications

Pathways for Fluorescence Quenching in 2-Aminopurine π-Stacked with Pyrimidine Nucleobases

Pathways for Fluorescence Quenching in 2-Aminopurine π-Stacked with Pyrimidine Nucleobases

State transitions in Chlamydomonas reinhardtii strongly modulate the functional size of photosystem II but not of photosystem I

Molecular Basis of Light Harvesting and Photoprotection in CP24

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