Observation of the solid-state photo-CIDNP effect in entire cells of cyanobacteria Synechocystis

Cyanobacteria are widely used as model organism of oxygenic photosynthesis due to being the simplest photosynthetic organisms containing both photosystem I and II (PSI and PSII). Photochemically induced dynamic nuclear polarization (photo-CIDNP) 13C magic-angle spinning (MAS) NMR is a powerful tool in understanding the photosynthesis machinery down to atomic level. Combined with selective isotope enrichment this technique has now opened the door to study primary charge separation in whole living cells. Here, we present the first photo-CIDNP observed in whole cells of the cyanobacterium Synechocystis

The solid-state photo-CIDNP effect

The solid-state photo-CIDNP effect is the occurrence of a non-Boltzmann nuclear spin polarization in rigid samples upon illumination. For solid-state NMR, which can detect this enhanced nuclear polarization as a strong modification of signal intensity, the effect allows for new classes of experiments. Currently, the photo- and spin-chemical machinery of various RCs is studied by photo-CIDNP MAS NMR in detail. Until now, the effect has only been observed at high magnetic fields with 13C and 15N MAS NMR and in natural photosynthetic RC preparations in which blocking of the acceptor leads to cyclic electron transfer. In terms of irreversible thermodynamics, the high-order spin structure of the initial radical pair can be considered as a transient order phenomenon emerging under non-equilibrium conditions and as a first manifestation of order in the photosynthetic process. The solid-state photo-CIDNP effect appears to be an intrinsic property of natural RCs. The conditions of its occurrence seem to be conserved in evolution. The effect may be based on the same fundamental principles as the highly optimized electron transfer. Hence, the effect may allow for guiding artificial photosynthesis

Non-perturbative methods for a chiral effective field theory of finite density nuclear systems

Recently we have developed a novel chiral power counting scheme for an effective field theory of nuclear matter with nucleons and pions as degrees of freedom [1]. It allows for a systematic expansion taking into account both local as well as pion-mediated multi-nucleon interactions. We apply this power counting in the present study to the evaluation of the pion self-energy and the energy density in nuclear and neutron matter at next-to-leading order. To implement this power counting in actual calculations we develop here a non-perturbative method based on Unitary Chiral Perturbation Theory for performing the required resummations. We show explicitly that the contributions to the pion self-energy with in-medium nucleon-nucleon interactions to this order cancel. The main trends for the energy density of symmetric nuclear and neutron matter are already reproduced at next-to-leading order. In addition, an accurate description of the neutron matter equation of state, as compared with sophisticated many-body calculations, is obtained by varying only slightly a subtraction constant around its expected value. The case of symmetric nuclear matter requires the introduction of an additional fine-tuned subtraction constant, parameterizing the effects from higher order contributions. With that, the empirical saturation point and the nuclear matter incompressiblity are well reproduced while the energy per nucleon as a function of density closely agrees with sophisticated calculations in the literature.Comment: 66 pages, 27 figures, 1 Table. Version to be published. New results are include

A dynamic model of reaction pathway effects on parahydrogen-induced nuclear spin polarization

A dynamic model for the calculation of parahydrogen (p-H-2) induced nuclear polarization (PHIP) of hydrogenation products is described which is based on the density matrix formalism. This formalism was proposed previously by Binsch for the calculation of NMR spectra broadened by chemical exchange between different sites. Using numerical simulations typical for actual experiments, it is shown that the PHIP patterns may depend not only on the type of experiment performed - e.g. ALTADENA (adiabatic longitudinal transport after dissociation engenders net alignment) in the absence and PASADENA (parahydrogen and synthesis allow dramatically enhanced nuclear alignment) in the presence of a magnetic field - but also on the pathways of the hydrogenation reaction, in which generally transition metal catalysts are involved. Of particular importance are the properties of possible reaction intermediates where the reactants are complexed alone or together to the catalyst. Indirect information from the PHIP pattern of the hydrogenation products on the intermediate can be obtained, in particular its chemical shifts, exchange and magnetic couplings, and the incoherent dihydrogen self-exchange. In addition, the regioselectivity of the hydrogenation step is a factor influencing the PHIP patterns. The model and the results obtained here provide, therefore, a theoretical link between various phenomena concerning the hydrogen mobility in transition metal catalysts, and PHIP is shown to be a valuable tool for obtaining information on the reaction intermediates

Detection of ppm Quantitites of Gaseous SO2 by Nanosize Organoplatinum Dendritic Sites Immobilised on a Quartz Microbalance

Sensor devices for the detection of low quantities of SO2 gas have been constructed which comprise organoplatinum receptor sites for the selective recognition of SO2 and a quartz crystal microbalance for the detection of small mass changes at the receptor sites

Homogeneous Hydrogenation in Supercritical Fluids Mediated by Colloidal Catalysts

As an intermediate form between homogeneous and heterogeneous catalysis, catalysts based on transition metal colloids have drawn a lot of attention in recent years. Mating advantages from different concepts of catalysis, they turn out to be highly active, selective, and, in addition, easily separated from other reaction components. Even though colloidal catalysts are widely used in conventional solvents, hardly anything is known about their reactivity in supercritical fluids such as supercritical carbon dioxide (scCO2). Furthermore, scCO2 is an especially attractive, non-toxic, and environmentally benign solvent for chemical reactions. When hydrogenations were conducted using polymer-supported colloidal Pd nanoparticles as catalysts in scCO2, we found turnover frequencies (TOFs) as high as 4 000 000 h-1 even at a reasonably low hydrogen pressures of 15 bar and temperatures of 50 °C. To our surprise, their reactivity turned out to be much higher than those of most other catalysts reported in the literature. The kinetics of their catalytic reactions in supercritical fluids has been investigated using in situ NMR in combination with a toroid cavity autoclave (TCA)