Search results for "energy transfer"

How activator ion concentration affects spectroscopic properties on Ba4Y3F17: Er3+, Yb3+, a new perspective up-conversion material

2018

Abstract Ba4Y3F17 with Er3+ and Yb3+, a promising material for up-conversion luminescence, was synthesized. Excellent isomorphic capacity was detected. Low-temperature measurements show that erbium ions are incorporated in multiple lattice positions, which is inconsistent with the current model of Ba4Y3F17 crystal lattice structure. Activator ion concentration has a different impact on 4S3/2 and 4F9/2, states (for the green and red luminescence, respectively) depopulation. Energy transfer from Er3+ 4S3/2 state to Yb3+ is observed even at low temperature (15 K) while Er-Er cross-relaxation is observed from 120 K and above. Yb3+ concentration has a great impact to red-to-green up-conversion l…

The first example of cofacial bis(dipyrrins)

2016

International audience; Two series of cofacial bis(dipyrrins) were prepared and their photophysical properties as well as their bimolecular fluorescence quenching with C-60 were investigated. DFT and TDDFT computations were also performed as a modeling tool to address the nature of the fluorescence state and the possible inter-chromophore interactions. Clearly, there is no evidence for such interactions and the bimolecular quenching of fluorescence, in comparison with mono-dipyrrins, indicates that C-60-bis(dipyrrin) contacts occur from the outside of the "mouth" of the cofacial structure.

Cover Picture: Dynamic Chemical Devices: Photoinduced Electron Transfer and Its Ion-Triggered Switching in Nanomechanical Butterfly-Type Bis(porphyri…

2006

Synthesis of an Acceptor–Donor–Acceptor Multichromophore Consisting of Terrylene and Perylene Diimides for Multistep Energy Transfer Studies

2016

Motivated by the results obtained from the investigation of singlet–singlet annihilation in a linear multichromophore comprising terrylene diimides (TDI) and perylene diimide (PDI) in 2010, we report the detailed process toward the successful synthesis of a TDI–PDI–TDI dyad. Ineffective synthetic pathways, which were necessary for the understanding of the step-by-step construction of the complex multichromophore, are described, leading toward a universal synthetic plan for multicomponent systems containing rylene diimides separated by rigid oligophenylene spacers.

Functional rearrangement of the light-harvesting antenna upon state transitions in a green alga

2014

AbstractState transitions in the green alga Chlamydomonas reinhardtii serve to balance excitation energy transfer to photosystem I (PSI) and to photosystem II (PSII) and possibly play a role as a photoprotective mechanism. Thus, light-harvesting complex II (LHCII) can switch between the photosystems consequently transferring more excitation energy to PSII (state 1) or to PSI (state 2) or can end up in LHCII-only domains. In this study, low-temperature (77 K) steady-state and time-resolved fluorescence measured on intact cells of Chlamydomonas reinhardtii shows that independently of the state excitation energy transfer from LHCII to PSI or to PSII occurs on two main timescales of <15 ps and …

A port-Hamiltonian Fluid-Structure Interaction Model for the Vocal folds ⁎ ⁎This work was supported by CONICYT-PFCHA/2017-21170472, and AC3E CONICYT-…

2018

Abstract Fluid-structure interaction models are of special interest for studying the energy transfer between the moving fluid and the mechanical structure in contact. The vocal folds are an example of a fluid-structure system, where the mechanical structure is usually modeled as a mass-spring-damper system. In particular, the estimation of the collision forces of the vocal folds is of high interest in the diagnosis of phonotraumatic voice pathologies. In this context, the port-Hamiltonian modeling framework focuses on the energy flux in the model and the interacting forces. In this paper, we develop a port-Hamiltonian fluid-structure interaction model based on the interconnection methodolog…

Identification and Characterization of a Single High-Affinity Fatty Acid Binding Site in Human Serum Albumin.

2017

A single high-affinity fatty acid binding site in the important human transport protein serum albumin (HSA) is identified and characterized using an NBD (7-nitrobenz-2-oxa-1,3-diazol-4-yl)-C12 fatty acid. This ligand exhibits a 1:1 binding stoichiometry in its HSA complex with high site-specificity. The complex dissociation constant is determined by titration experiments as well as radioactive equilibrium dialysis. Competition experiments with the known HSA-binding drugs warfarin and ibuprofen confirm the new binding site to be different from Sudlow-sites I and II. These binding studies are extended to other albumin binders and fatty acid derivatives. Furthermore an X-ray crystal structure …

Aza-macrocyclic triphenylamine ligands for G-quadruplex recognition

2018

A new series of triphenylamine-based ligands with one (TPA1PY), two (TPA2PY) or three pendant aza-macrocycle(s) (TPA3PY) has been synthesised and studied by means of pH-metric titrations, UV/Vis spectroscopy and fluorescence experiments. The affinity of these ligands for G-quadruplex (G4) DNA and the selectivity they show for G4s over duplex DNA were investigated by Forster resonance energy transfer (FRET) melting assays, fluorimetric titrations and circular dichroism spectroscopy. Interestingly, the interactions of the bi- and especially the tri-branched ligands with G4s lead to a very intense redshifted fluorescence emission band that may be associated with intermolecular aggregation betw…

FRET biosensor allows spatio-temporal observation of shear stress-induced polar RhoGDIα activation

2018

Rho GDP-dissociation inhibitor α (RhoGDIα) is a known negative regulator of the Rho family that shuts off GDP/GTP cycling and cytoplasm/membrane translocation to regulate cell migration. However, to our knowledge, no reports are available that focus on how the RhoGDIα-Rho GTPases complex is activated by laminar flow through exploring the activation of RhoGDIα itself. Here, we constructed a new biosensor using fluorescence resonance energy transfer (FRET) technology to measure the spatio-temporal activation of RhoGDIα in its binding with Rho GTPases in living HeLa cells. Using this biosensor, we find that the dissociation of the RhoGDIα-Rho GTPases complex is increased by shear stress, and i…

Free energy profiles for two ubiquitous damaging agents: methylation and hydroxylation of guanine in B-DNA

2017

International audience; DNA methylation and hydroxylation are two ubiquitous reactions in DNA damage induction, yet insights are scarce concerning the free energy of activation within B-DNA. We resort to multiscale simulations to investigate the attack of a hydroxyl radical and of the primary diazonium onto a guanine embedded in a solvated dodecamer. Reaction free energy profiles characterize two strongly exergonic processes, yet allow unprecedented quantification of the barrier towards this damage reaction, not higher than 6 kcal mol−1 and sometimes inexistent, and of the exergonicities. In the case of the [G(C8)-OH]˙ intermediate, we challenge the functional dependence of such simulations…