Search results for "Energy Transfer"
showing 10 items of 240 documents
Single- and Double-Strand Breaks of Dry DNA Exposed to Protons at Bragg-Peak Energies
2017
International audience; Ultrathin layers (<20 nm) of pBR322 plasmid DNA were deposited onto 2.5 μm thick polyester films and exposed to proton Bragg-peak energies (90–3000 keV) at various fluences. A quantitative analysis of radio-induced DNA damage is reported here in terms of single- and double-strand breaks (SSB and DSB, respectively). The corresponding yields as well as G-values and the cross sections exhibit fairly good agreement with the rare available data, stemming from close experimental conditions, namely, based on α particle irradiation. SSB/DSB rates appear to be linear when plotted against linear energy transfer (LET) in the whole energy range studied. All the data present a ma…
Adenine and 2-aminopurine: Paradigms of modern theoretical photochemistry
2006
Distinct photophysical behavior of nucleobase adenine and its constitutional isomer, 2-aminopurine, has been studied by using quantum chemical methods, in particular an accurate ab initio multiconfigurational second-order perturbation theory. After light irradiation, the efficient, ultrafast energy dissipation observed for nonfluorescent 9H-adenine is explained here by the nonradiative internal conversion process taking place along a barrierless reaction path from the initially populated 1 (ππ* L a ) excited state toward a low-lying conical intersection (CI) connected with the ground state. In contrast, the strong fluorescence recorded for 2-aminopurine at 4.0 eV with large decay lifetime …
Energy transfer in diiodoBodipy-grafted upconversion nanohybrids.
2015
Steady-state and time-resolved emission studies on nanohybrids consisting of NaYF4:Yb,Er and a diiodo-substituted Bodipy (UCNP-IBDP) show that the Yb(3+) metastable state, formed after absorption of a near-infrared (NIR) photon, can decay via two competitive energy transfer processes: sensitization of IBDP after absorption of a second NIR photon and population of Er(3+) excited states.
Through space singlet-singlet and triplet-triplet energy transfers in cofacial bisporphyrins held by the carbazoyl spacer
2007
The through space singlet-singlet and triplet-triplet energy transfers in cofacial bis(etio-porphyrins) rigidly held by the carbazoyl spacer were investigated. The studies on singlet-singlet transfer, which operates via a Förster mechanism, were performed using the zinc porphyrin and free base chromophores as energy donor and acceptor, respectively, while the investigation on triplet-triplet processes was performed using the palladium porphyrin, and the zinc porphyrin and free base chromophores as donor and acceptors, respectively. The rate for singlet-singlet transfer ( k ET ( singlet )) is unexpectedly slower than that reported for other similar, rigidly held bisporphyrins such as H 2( D…
Influence of Surface-Related Phenomena on Mechanism, Selectivity, and Conversion of TiO2 -Induced Photocatalytic Reactions
2018
Heterogeneous photocatalysis is the result of an inextricable connection of several factors differently contributing to the overall process. Photon absorption is the “sine qua non” condition for the reaction to occur. In fact, photons can be considered as immaterial reactants, and all of the phenomena related to the interaction of light–matter play a prominent role. However, other factors contribute in a concerted way to address the reaction, so that the relative contribution of each of them is often difficult to evaluate. In this framework, the present paper highlights some aspects of the interaction of TiO 2 surface-adsorbate species that could be underestimated and their influence on the…
Up-conversion and Photoluminescence in Er3+ Single Crystal MgAl-spinel
2015
Abstract Traditional and up-conversion luminescence of MgAl 2 O 4 single crystal doped with erbium ions obtained by the Verneuil method has been investigated. The time resolved spectral measurements of the green and red up-conversion luminescence bands show that a build-up part is present in the up-conversion luminescence kinetics. This means that energy transfer process is involved in the creation of the luminescence. Considering rather small concentration of Er 3+ in the material (0.12 mass %), the expected up-conversion mechanism should be excited state absorption since the average distance between erbium ions is high. The above-mentioned considerations suggest that clustering of the act…
Reconfigurable DNA Origami Nanocapsule for pH-Controlled Encapsulation and Display of Cargo
2019
DNA nanotechnology provides a toolbox for creating custom and precise nanostructures with nanometer-level accuracy. These nano-objects are often static by nature and serve as versatile templates for assembling various molecular components in a user-defined way. In addition to the static structures, the intrinsic programmability of DNA nanostructures allows the design of dynamic devices that can perform predefined tasks when triggered with external stimuli, such as drug delivery vehicles whose cargo display or release can be triggered with a specified physical or chemical cue in the biological environment. Here, we present a DNA origami nanocapsule that can be loaded with cargo and reversibl…
Geothermal energy release at the Solfatara of Pozzuoli (Phlegraean Fields): Phreatic and phreatomagmatic explosion risk implications
1984
The H2O, CO2 and H2S outputs at the Solfatara of Pozzuoli have been measured and a map of the exhaling areas has also been made. The energy released at the surface by the fluids has been estimated to be 1019 ergs/day. The presence of aquifers at Phlegraean Fields increases the phreatic and phreatomagmatic explosion risk. Our results suggest that even if an uprising magma may interact with water at depth, an explosion could occur only at the shallow levels of a few hundred meters. Since the transfer of energy toward the surface is favoured by the presence of fractures, a detailed analysis of the deep fracture network would help to evaluate the risk levels of the various areas of Phlegraean F…
Nitrated Fatty Acids Modulate the Physical Properties of Model Membranes and the Structure of Transmembrane Proteins
2017
Nitrated fatty acids (NO2 -FAs) act as anti-inflammatory signal mediators, albeit the molecular mechanisms behind NO2 -FAs' influence on diverse metabolic and signaling pathways in inflamed tissues are essentially elusive. Here, we combine fluorescence measurements with surface-specific sum frequency generation vibrational spectroscopy and coarse-grained computer simulations to demonstrate that NO2 -FAs alter lipid organization by accumulation at the membrane-water interface. As the function of membrane proteins strongly depends on both, protein structure as well as membrane properties, we consecutively follow the structural dynamics of an integral membrane protein in presence of NO2 -FAs. …
Conformational Dynamics of the Dengue Virus Protease Revealed by Fluorescence Correlation and Single-Molecule FRET Studies.
2021
The dengue virus protease (DENV-PR) represents an attractive target for counteracting DENV infections. It is generally assumed that DENV-PR can exist in an open and a closed conformation and that active site directed ligands stabilize the closed state. While crystal structures of both the open and the closed conformation were successfully resolved, information about the prevalence of these conformations in solution remains elusive. Herein, we address the question of whether there is an equilibrium between different conformations in solution which can be influenced by addition of a competitive inhibitor. To this end, DENV-PR was statistically labeled by two dye molecules constituting a FRET …