Metal nanoparticle alters adenine induced charge transfer kinetics of vitamin K3 in magnetic field

In this article, we highlight the alterations in the photoinduced electron transfer (ET) and hydrogen atom transfer (HAT) pathways between an anti-tumor drug vitamin-K3 (MQ) and a nucleobase adenine (ADN) in the presence of gold (Au) and iron (Fe) nanoparticles (NPs). Inside the confined micellar media, with laser flash photolysis corroborated with an external magnetic field (MF), we have detected the transient geminate radicals of MQ and ADN, photo-generated through ET and HAT. We observe that the presence of AuNP on the MQ-ADN complex (^(Au)MQ-ADN) assists HAT by limiting the ET channel, on the other hand, FeNP on the MQ-ADN complex (^(Fe)MQ-ADN) mostly favors a facile PET. We hypothesize that through selective interactions of the ADN molecules with AuNP and MQ molecules with FeNP, a preferential HAT and PET process is eased. The enhanced HAT and PET have been confirmed by the escape yields of radical intermediates by time-resolved transient absorption spectroscopy in the presence of MF

Design and Synthesis of Fluorescent Carbon Dot Polymer and Deciphering Its Electronic Structure

Herein we report the one-pot synthesis of a fluorescent polymer-like material (pCD) by exploiting ruthenium-doped carbon dots (CDs) as building blocks. The unusual spectral profiles of pCDswith double-humped periodic excitation dependent photoluminescence (EDPL), and the regular changes in their corresponding average lifetime indicate the formation of high energy donor states and low energy aggregated states due to the overlap of molecular orbitals throughout the chemically switchable π-network of CDs on polymerization. To probe the electronic distribution of pCDs, we have investigated the occurrence of photoinduced electron transfer with a model electron acceptor, menadione using transient absorption technique, corroborated with low magnetic field, followed by identification of the transient radical ions generated through electron transfer. The experimentally obtained B_(1/2) value, a measure of the hyperfine interactions present in the system, indicates the presence of highly conjugated π-electron cloud in pCDs. The mechanism of formation of pCDs and the entire experimental findings have further been investigated through molecular modeling and computational modeling. The DFT calculations demonstrated probable electronic transitions from the surface moieties of pCDs to the tethered ligands

Development of Next-Generation Fluorescent Turn-On Sensor to Simultaneously Detect and Detoxify Mercury in Living Samples

Strategies for simultaneous detection and detoxification of Hg^(2+) using a single sensor from biological and environmental samples are limited and have not been realized in living organisms so far. We report a highly selective, small molecule “turn-on” fluorescent sensor, PYDMSA, based on the cationic dye Pyronin Y (PY) and chelating agent meso-2,3-dimercaptosuccinic acid (DMSA) for the simultaneous detection and detoxification of inorganic mercury (Hg^(2+)). After Hg^(2+) detection, concomitant detoxification was carried out with sufficient efficacy in living samples, which makes the sensor unique. PYDMSA exhibits high selectivity for Hg^(2+) over other competing metal ions with an experimental detection limit of ∼300 pM in aqueous buffer solution. When PYDMSA reacts with Hg2+, the CS–C^9 bond in the sensor gets cleaved. This results in the “turn-on” response of the fluorescence probe with a concomitant release of one equivalent of water-soluble Hg^(2+)–DMSA complex which leads to a synchronous detoxifying effect. The sensor by itself is nontoxic to cells in culture and has been used to monitor the real-time uptake of Hg^(2+) in live cells and zebrafish larvae. Thus, PYDMSA is a unique sensor which can be used to detect and detoxify mercury at the same time in living samples

Redox Modifications of Carbon Dots Shape Their Optoelectronics

Carbon dots (CDs) are 1–10 nm scaled complex nanostructures with a wide range of applications and show unconventional photophysical behavior upon excitation. In this article, we have unveiled some of the underlying mechanisms and excited state dynamics of CDs by perturbing their interface with oxidizing and reducing agents. With no substantial alteration in size of surface-treated oxidized (^OCDs), reduced (^RCDs), and untreated CDs (^UCDs), we observe marked changes in their charge transport properties and diverse spectral signatures in singlet and triplet excited states. Fine tuning of the spectral behavior of nanomaterials is often treated as an outcome of quantum confinement of the excitons. Herein with different spectroscopic techniques along with conducting atomic force microscopy and triplet–triplet absorption, we elucidate that, not just confinement, the structural modification at the surface also dictates optoelectronic behavior by altering some properties such as energy band gap, quantum tunneling across the metal–CD–metal junction, and yield of triplet excitons

Design and Synthesis of Fluorescent Carbon Dot Polymer and Deciphering Its Electronic Structure

Herein we report the one-pot synthesis of a fluorescent polymer-like material (pCD) by exploiting ruthenium-doped carbon dots (CDs) as building blocks. The unusual spectral profiles of pCDswith double-humped periodic excitation dependent photoluminescence (EDPL), and the regular changes in their corresponding average lifetime indicate the formation of high energy donor states and low energy aggregated states due to the overlap of molecular orbitals throughout the chemically switchable π-network of CDs on polymerization. To probe the electronic distribution of pCDs, we have investigated the occurrence of photoinduced electron transfer with a model electron acceptor, menadione using transient absorption technique, corroborated with low magnetic field, followed by identification of the transient radical ions generated through electron transfer. The experimentally obtained B_(1/2) value, a measure of the hyperfine interactions present in the system, indicates the presence of highly conjugated π-electron cloud in pCDs. The mechanism of formation of pCDs and the entire experimental findings have further been investigated through molecular modeling and computational modeling. The DFT calculations demonstrated probable electronic transitions from the surface moieties of pCDs to the tethered ligands

Nanocolumnar Crystalline Vanadium Oxide-Molybdenum Oxide Antireflective Smart Thin Films with Superior Nanomechanical Properties

Vanadium oxide-molybdenum oxide (VO-MO) thin (21-475 nm) films were grown on quartz and silicon substrates by pulsed RF magnetron sputtering technique by altering the RF power from 100 to 600 W. Crystalline VO-MO thin films showed the mixed phases of vanadium oxides e.g., V2O5, V2O3 and VO2 along with MoO3. Reversible or smart transition was found to occur just above the room temperature i.e., at similar to 45-50 degrees C. The VO-MO films deposited on quartz showed a gradual decrease in transmittance with increase in film thickness. But, the VO-MO films on silicon exhibited reflectance that was significantly lower than that of the substrate. Further, the effect of low temperature (i.e., 100 degrees C) vacuum (10(-5) mbar) annealing on optical properties e.g., solar absorptance, transmittance and reflectance as well as the optical constants e.g., optical band gap, refractive index and extinction coefficient were studied. Sheet resistance, oxidation state and nanomechanical properties e.g., nanohardness and elastic modulus of the VO-MO thin films were also investigated in as-deposited condition as well as after the vacuum annealing treatment. Finally, the combination of the nanoindentation technique and the finite element modeling (FEM) was employed to investigate yield stress and von Mises stress distribution of the VO-MO thin films

Determining the pharmacokinetics of nicotinic drugs in the endoplasmic reticulum using biosensors

Nicotine dependence is thought to arise in part because nicotine permeates into the endoplasmic reticulum (ER), where it binds to nicotinic receptors (nAChRs) and begins an “inside-out” pathway that leads to up-regulation of nAChRs on the plasma membrane. However, the dynamics of nicotine entry into the ER are unquantified. Here, we develop a family of genetically encoded fluorescent biosensors for nicotine, termed iNicSnFRs. The iNicSnFRs are fusions between two proteins: a circularly permutated GFP and a periplasmic choline-/betaine-binding protein engineered to bind nicotine. The biosensors iNicSnFR3a and iNicSnFR3b respond to nicotine by increasing fluorescence at [nicotine] 75%. Reducing nicotine intake by 10-fold decreases activation to ∼20%. iNicSnFR3a and iNicSnFR3b also sense the smoking cessation drug varenicline, revealing that varenicline also permeates into the ER within seconds. Our iNicSnFRs enable optical subcellular pharmacokinetics for nicotine and varenicline during an early event in the inside-out pathway

Débat avec les responsables scientifiques de l’axe 3

Valérie Carayol : Vous avez dit que « dans la mêlée du direct, nous participons plutôt que nous symbolisons » et que « l’induction se vit au présent ». Hier, avec Wolfgang Settekorn qui nous a parlé de métaphorisations mutuelles avec des exemples visuels et avec Philippe Breton qui nous a parlé d’amalgame, on avait déjà esquissé un rapprochement entre l’induction et les dynamiques spatiales, pas obligatoirement une dynamique temporelle. Est-ce que vous pourriez préciser cette idée du direct, ..