Search results for "FOS"
showing 10 items of 15075 documents
Anomalous Structure and Scaling of Ring Polymer Brushes
2011
A comparative simulation study of polymer brushes formed by grafting at a planar surface either flexible linear polymers (chain length $N_L$) or (non-catenated) ring polymers (chain length $N_R=2 N_L$) is presented. Two distinct off-lattice models are studied, one by Monte Carlo methods, the other by Molecular Dynamics, using a fast implementation on graphics processing units (GPUs). It is shown that the monomer density profiles $\rho(z)$ in the $z$-direction perpendicular to the surface for rings and linear chains are practically identical, $\rho_R(2 N_L, z)=\rho_L(N_L, z)$. The same applies to the pressure, exerted on a piston at hight z, as well. While the gyration radii components of ri…
Structure of bottle-brush polymers in solution: A Monte Carlo test of models for the scattering function
2008
Extensive Monte Carlo results are presented for a lattice model of a bottle-brush polymer under good solvent or Theta solvent conditions. Varying the side chain length, backbone length, and the grafting density for a rigid straight backbone, both radial density profiles of monomers and side chain ends are obtained, as well as structure factors describing the scattering from a single side chain and from the total bottle-brush polymer. To describe the structure in the interior of a very long bottle-brush, a periodic boundary condition in the direction along the backbone is used, and to describe effects due to the finiteness of the backbone length, a second set of simulations with free ends of…
A fast Monte Carlo algorithm for studying bottle-brush polymers
2011
Obtaining reliable estimates of the statistical properties of complex macromolecules by computer simulation is a task that requires high computational effort as well as the development of highly efficient simulation algorithms. We present here an algorithm combining local moves, the pivot algorithm, and an adjustable simulation lattice box for simulating dilute systems of bottle-brush polymers with a flexible backbone and flexible side chains under good solvent conditions. Applying this algorithm to the bond fluctuation model, very precise estimates of the mean square end-to-end distances and gyration radii of the backbone and side chains are obtained, and the conformational properties of s…
Conformational studies of bottle-brush polymers absorbed on a flat solid surface.
2010
The adsorption of a bottle-brush polymer end-grafted with one chain end of its backbone to a flat substrate surface is studied by Monte Carlo simulation of a coarse-grained model, that previously has been characterized in the bulk, assuming a dilute solution under good solvent conditions. Applying the bond fluctuation model on the simple cubic lattice, we vary the backbone chain length $N_b$ from $N_b=67$ to $N_b = 259$ effective monomeric units, the side chain length $N$ from N=6 to N=48, and the grafting density $\sigma=1$, i.e., parameters that correspond well to the experimentally accessible range. When the adsorption energy strength $\epsilon$ is varied, we find that the adsorption tra…
Effect of Glufosinate (Phosphinothricin) and Inhibitors of Photorespiration on Photosynthesis and Ribulose-1,5-Bisphosphate Carboxylase Activity
1992
Summary Glufosinate (phosphinothricin) irreversibly inhibits glutamine synthetase and leads to a great decrease in the amino acids glutamine, glutamate, aspartate, serine, glycine and alanine. Due to the lack of glutamate and serine, the transamination of glyoxylate into glycine in the course of photorespiration cannot take place. The inhibition of this part of the photorespiratory process plays the essential role with respect to the photosynthesis inhibition caused by PPT under atmospheric conditions. After addition of different photorespiration or Calvin cycle intermediates to phosphinothricin no decrease in photosynthesis inhibition can be measured. This suggests that photosynthesis inhi…
The cyclic [N(PiPr2E)2]+ (E = Se, Te) cations: a new class of inorganic ring system.
2006
The two-electron oxidation of [(tmeda)NaN(PiPr2E)2] with iodine produces the cyclic [N(PiPr2E)2]+ (E = Se, Te) cations, which exhibit long E–E bonds in the iodide salts. peerReviewed
Theory and Simulation of Multiphase Polymer Systems
2010
The theory of multiphase polymer systems has a venerable tradition. The 'classical' theory of polymer demixing, the Flory-Huggins theory, was developed already in the forties of the last century. It is still the starting point for most current approaches -- be they improved theories for polymer (im)miscibility that take into account the microscopic structure of blends more accurately, or sophisticated field theories that allow to study inhomogeneous multicomponent systems of polymers with arbitrary architectures in arbitrary geometries. In contrast, simulations of multiphase polymer systems are relatively young. They are still limited by the fact that one must simulate a large number of lar…
Inhibitory Action of Glufosinate on Photosynthesis
1993
Glufosinate (phosphinothricin) irreversibly blocks the glutamine synthetase which subsequently gives rise to an accumulation of ammonium and to a strong decrease in some amino acids, especially glutamine and glutamate. Under atmospheric conditions (400 ppm CO2, 21% O2) glufosinate causes a rapid inhibition of photosynthesis, too. H ow ever, under non-photo respiratory conditions (1000 ppm CO2, 2% O2) only a slight inhibition of photosynthesis occurs with glufosinate. Since under both conditions an accumulation of ammonium occurs, it is concluded that inhibition of photosynthesis is not induced by the higher concentrations of ammonium. The results rather suggest that the absence of amino don…
Metabolic cross-talk between pathways of terpenoid backbone biosynthesis in spike lavender
2015
Abstract The metabolic cross-talk between the mevalonate (MVA) and the methylerythritol phosphate (MEP) pathways in developing spike lavender ( Lavandula latifolia Med) was analyzed using specific inhibitors and on the basis of 13 C-labeling experiments. The presence of mevinolin (MEV), an inhibitor of the MVA pathway, at concentrations higher than 0.5 μM significantly reduced plant development, but not the synthesis of chlorophylls and carotenoids. On the other hand, fosmidomycin (FSM), an inhibitor of the MEP pathway, at concentrations higher than 20 μM blocked the synthesis of chlorophyll, carotenoids and essential oils, and significantly reduced stem development. Notably, 1.2 mM MVA cou…
[21] Assay of blood glutathione oxidation during physical exercise
1995
Publisher Summary This chapter describes a method to accurately measure glutathione (GSH) and glutathione disulfide (GSSG) in the blood of humans and animals that perform physical exercise. With this method, it is possible to assess the oxidative stress associated with physical exercise by measuring changes in the blood GSH/GSSG ratio. Glutathione measurement is performed by a modification of the glutathione S -transferase method of Brigelius et al. This is based on the conjugation of chlorodinitrobenzene with GSH catalyzed by glutathione S -transferase. The adduct formed, S-(2,4-dinitrophenyl)glutathione, exhibits a maximum of absorbance at 340 nm. The precipitation of proteins is carried …