Assessment of noncollinear spin-flip Tamm-Dancoff approximation time-dependent density-functional theory for the photochemical ring-opening of oxirane.

Under the usual assumption of noninteracting v-representability, density-functional theory (DFT) together with time-dependent DFT (TDDFT) provide a formally exact single-reference method suitable for the theoretical description of the electronic excited-states of large molecules, and hence for the description of excited-state potential energy surfaces important for photochemistry. The quality of this single-reference description is limited in practice by the need to use approximate exchange-correlation functionals. In particular it is far from clear how well approximations used in contemporary practical TDDFT calculations can describe funnel regions such as avoided crossings and conical intersections.

Priors for the Bayesian star paradox.

We show that the Bayesian star paradox, first proved mathematically by Steel and Matsen for a specific class of prior distributions, occurs in a wider context including less regular, possibly discontinuous, prior distributions.

Iodination of verapamil for a stronger induction of death, through GSH efflux, of cancer cells overexpressing MRP1.

The multidrug resistance protein 1 (MRP1), involved in multidrug resistance (MDR) of cancer cells, was found to be modulated by verapamil, through stimulation of GSH transport, leading to apoptosis of MRP1-overexpressing cells. In this study, various iodinated derivatives of verapamil were synthesized, including iodination on the B ring, known to be involved in verapamil cardiotoxicity, and assayed for the stimulation of GSH efflux by MRP1. The iodination, for nearly all compounds, led to a higher stimulation of GSH efflux.

A scheme for solving the plane-plane challenge in force measurements at the nanoscale.

Non-contact interaction between two parallel flat surfaces is a central paradigm in sciences. This situation is the starting point for a wealth of different models: the capacitor description in electrostatics, hydrodynamic flow, thermal exchange, the Casimir force, direct contact study, third body confinement such as liquids or films of soft condensed matter. The control of parallelism is so demanding that no versatile single force machine in this geometry has been proposed so far.

A simple dynamic model of respiratory pump.

To study the interaction of forces that produce chest wall motion, we propose a model based on the lever system of Hillman and Finucane (J Appl Physiol 63(3):951-961, 1987) and introduce some dynamic properties of the respiratory system. The passive elements (rib cage and abdomen) are considered as elastic compartments linked to the open air via a resistive tube, an image of airways. The respiratory muscles (active) force is applied to both compartments.

Reversible apical coordination of imidazole between the Ni(III) and Ni(II) oxidation states of a dithiolate complex: a process related to the Ni superoxide dismutase.

A bisamine aliphatic dithiolate [Ni(II)N(2)S(2)] complex that does yield a metal-based oxidation has been synthesized. A square pyramidal [Ni(III)N(3)S(2)](+) complex is generated by electrochemical oxidation in the presence of imidazole, mimicking the redox structural changes of NiSOD. In addition, EPR measurements coupled to DFT calculations demonstrate that the metal character in the redox active orbital increases drastically upon imidazole binding, implicating that these geometrical modifications are crucial for the stabilization of the Ni(III) state.

Almost ideal 1D water diffusion in imogolite nanotubes evidenced by NMR relaxometry.

The longitudinal proton relaxation rates R(1) of water diffusing inside synthetic aluminium silicate imogolite nanotubes are measured by fast field-cycling NMR for frequencies between 0.02 and 35 MHz at 25, 37 and 50 degrees C. We give analytical expressions of the dominant intermolecular dipolar spin-spin contribution to R(1) and to the transverse relaxation rate R(2).

Giant slip lengths of a simple fluid at vibrating solid interfaces.

It has been shown recently [A. Siria, A. Drezet, F.

Post-translational membrane sorting of the Toxoplasma gondii GRA6 protein into the parasite-containing vacuole is driven by its N-terminal domain.

How eukaryotic pathogens export and sort membrane-bound proteins destined for host-cell compartments is still poorly understood. The dense granules of the intracellular protozoan Toxoplasma gondii constitute an unusual secretory pathway that allows soluble export of the GRA proteins which become membrane-associated within the parasite replicative vacuole. This process relies on both the segregation of the proteins routed to the dense granules from those destined to the parasite plasma membrane and on the sorting of the secreted GRA proteins to their proper final membranous system.

Comparison of kinetic and dynamical models of DNA-protein interaction and facilitated diffusion.

It has long been asserted that proteins such as transcription factors may locate their target in DNA sequences at rates that surpass by several orders of magnitude the three-dimensional diffusion limit thanks to facilitated diffusion, that is, the combination of one-dimensional (sliding along the DNA) and three-dimensional diffusion. This claim has been supported throughout the years by several mass action kinetic models, while the dynamical model we proposed recently (J. Chem.

Phylogenetic distances for neighbour dependent substitution processes.

We consider models of nucleotidic substitution processes where the rate of substitution at a given site depends on the state of the neighbours of the site. We first estimate the time elapsed between an ancestral sequence at stationarity and a present sequence. Second, assuming that two sequences are issued from a common ancestral sequence at stationarity, we estimate the time since divergence.

Multispecies breath analysis faster than a single respiratory cycle by optical-feedback cavity-enhanced absorption spectroscopy.

We demonstrate a first application, of optical-feedback cavity-enhanced absorption spectroscopy (OF-CEAS) to breath analysis in a medical environment. Noninvasive monitoring of trace species in exhaled air was performed simultaneous to spirometric measurements on patients at Bichat Hospital (Paris). The high selectivity of the OF-CEAS spectrometer and a time response of 0.

Development of a mechanism for nitrate photochemistry in snow.

A reaction mechanism to reproduce photochemical processes in the snow is reported. We developed a box model to represent snow chemistry. Constrained by laboratory experiments carried out with artificial snow, we deduced first a reaction mechanism for N-containing species including 13 reactions.

Label-free femtomolar detection of target DNA by impedimetric DNA sensor based on poly(pyrrole-nitrilotriacetic acid) film.

An ultrahigh performance impedimetric DNA sensor is presented showing detection limits in the femtomolar range. This electrochemical setup was constructed initially by electrogeneration of poly(11-pyrrol-1-yl-undecanoic acid N(alpha'),N(alpha)-bis(carboxymethyl)-L-lysine amide) (poly(pyrrole-NTA)) film. The latter was then modified by the coordination of Cu(2+) ions onto the chelating NTA centers followed by the immobilization of the ssHIV-DNA previously modified by a polyhistidine tag by affinity binding.

Soluble heterometallic coordination polymers based on a bis-terpyridine-functionalized dioxocyclam ligand.

Soluble homo- and heterometallic coordination polymers containing transition metal cations (Cu(2+), Fe(2+), Co(2+), and Ni(2+) ions) were prepared in a two-step procedure using a polytopic bis(terpyridine)dioxocyclam ligand 1H(2) (dioxocyclam = 1,4,8,11-tetraazacyclotetradecane-5,7-dione). These supramolecular systems incorporate two different metal complexes, the metal cations being located both between two terpyridine units and in the macrocyclic framework. The characterization of these soluble architectures was investigated by cyclic voltammetry, mass spectrometry, viscosimetry, and UV-vis absorption and electron paramagnetic resonance (EPR) spectroscopies.

Why do red blood cells have asymmetric shapes even in a symmetric flow?

Understanding why red blood cells (RBCs) move with an asymmetric shape (slipperlike shape) in small blood vessels is a long-standing puzzle in blood circulatory research. By considering a vesicle (a model system for RBCs), we discovered that the slipper shape results from a loss in stability of the symmetric shape. It is shown that the adoption of a slipper shape causes a significant decrease in the velocity difference between the cell and the imposed flow, thus providing higher flow efficiency for RBCs.

Phase instability and coarsening in two dimensions.

Instabilities and pattern formation is the rule in nonequilibrium systems. Selection of a persistent length scale or coarsening (increase in the length scale with time) are the two major alternatives. When and under which conditions one dynamics prevails over the other is a long-standing problem, particularly beyond one dimension.

Regulation of iron homeostasis in Arabidopsis thaliana by the clock regulator time for coffee.

In plants, iron homeostasis is tightly regulated to supply sufficient amounts of this metal for an optimal growth while preventing excess accumulation to avoid oxidative stress. To identify new regulators of iron homeostasis, a luciferase-based genetic screen using the Arabidopsis AtFer1 ferritin promoter as a target was developed. This screen identified TIME FOR COFFEE (TIC) as a regulator of AtFer1 gene expression.

Trinuclear terpyridine frustrated spin system with a Mn(IV)3O4 core: synthesis, physical characterization, and quantum chemical modeling of its magnetic properties.

The trinuclear oxo bridged manganese cluster, [Mn(IV)(3)O(4)(terpy)(terpyO(2))(2)(H(2)O)](S(2)O(8))(2) (5) (terpy = 2,2':2'',6'-terpyridine and terpyO(2) = 2,2':2'',6'-terpyridine 1,1''-dioxide), was isolated in an acidic aqueous medium from the reaction of MnSO(4), terpy, and oxone as chemical oxidant. The terpyO(2) ligands were generated in situ during the synthesis by partial oxidation of terpy. The complex crystallizes in the monoclinic space group P21/n with a = 14.

Tracing the Entropy along a Reactive Pathway: The Energy As a Generalized Reaction Coordinate.

By using metadynamics at a temperature T0 we reconstruct the free energy FT0(E,s) as a function of the potential energy E and of a geometrical variable s. We show here that from FT0(E,s) one can estimate the free energy also at a different temperature. This allows tracing the entropy and characterizing the properties of molecular systems at all temperatures by a single simulation.

Dynamic aspects of TCRalpha gene recombination: qualitative and quantitative assessments of the TCRalpha chain repertoire in man and mouse.

Most T-lymphocytes express a highly specific antigen receptor (TCR) on their cell surface, consisting of a clonotypic alphabeta-heterodimer. Both alpha- and beta chains are products of somatic rearrangements of V, (D) and J gene segments encoded on the respective loci. The qualitative, quantitative and dynamic aspects of the TCRalpha chain repertoire of humans and mice have been difficult to estimate, mainly due to locus complexity.

Viscous cavity damping of a microlever in a simple fluid.

We consider the problem of oscillation damping in air of a thermally actuated microlever as it gradually approaches an infinite wall in parallel geometry. As the gap is decreased from 20 microm down to 400 nm, we observe the increasing damping of the lever Brownian motion in the fluid laminar regime. This manifests itself as a linear decrease in the lever quality factor accompanied by a dramatic softening of its resonance, and eventually leads to the freezing of the CL oscillation.

Multifrequency high-field EPR investigation of a mononuclear manganese(IV) complex.

Electronic properties of [Mn(IV)(tacn)(OMe)(3)](+), especially the axial zero field splitting term D, which characterizes the magnetic anisotropy, have been investigated by multifrequency high-field EPR.

A MEMS-based high frequency x-ray chopper.

Time-resolved x-ray experiments require intensity modulation at high frequencies (advanced rotating choppers have nowadays reached the kHz range). We here demonstrate that a silicon microlever oscillating at 13 kHz with nanometric amplitude can be used as a high frequency x-ray chopper. We claim that using micro-and nanoelectromechanical systems (MEMS and NEMS), it will be possible to achieve higher frequencies in excess of hundreds of megahertz.

Vesicles in Poiseuille flow.

Blood microcirculation critically depends on the migration of red cells towards the flow centerline. We identify theoretically the ratio of the inner over the outer fluid viscosities lambda as a key parameter. At low lambda, the vesicle deforms into a tank-treading ellipsoid shape far away from the flow centerline.