Crystallization of Arthrobacter sp. strain 1C N-(1-D-carboxyethyl)-L-norvaline dehydrogenase and its complex with NAD+

The novel NAD+-linked opine dehydrogenase from a soil isolate Arthrobacter sp. strain 1C belongs to an enzyme superfamily whose members exhibit quite diverse substrate specificites. Crystals of this opine dehydrogenase, obtained in the presence or absence of co-factor and substrates, have been shown to diffract to beyond 1.8 ? resolution. X-ray precession photographs have established that the crystals belong to space group P21212, with cell parameters a = 104.9, b = 80.0, c = 45.5 ? and a single subunit in the asymmetric unit. The elucidation of the three-dimensional structure of this enzyme will provide a structural framework for this novel class of dehydrogenases to enable a comparison to be made with other enzyme families and also as the basis for mutagenesis experiments directed towards the production of natural and synthetic opine-type compounds containing two chiral centres.     

Pore-Scale Level Set Simulations of Capillary-Controlled Displacement with Adaptive Mesh Refinement

Transport in Porous Media - Multiphase flow simulations on imaged porous rock structures require numerical methods that are accurate and robust when applied on complex geometries. A key element in...     

An experimental analysis of fluctuating temperature measurements using hot-wires at different overheats

Adjacent parallel hot-wire anemometers at different temperatures have sometimes been used to measure fluctuating temperatures in turbulent flows. This work presents an extensive experimental comparison of temperatures measured with a parallel-wire probe to temperatures simultaneously measured with a standard cold-wire probe. The results show the parallel-wire probe to work well in low intensity flows with temperature signals which are not too small. However, the parallel-wire probe temperature measurements are not accurate for high turbulence intensities or for small temperature signals, and in general the cold-wire system is probably to be preferred.     

Nanoparticulate materials and regulatory policy in Europe: An analysis of stakeholder perspectives

The novel properties of nanoparticulate materials (NPM) and the rapid development of NPM based products have raised many unanswered questions and concerns by different stakeholders over its consequences for the environment and human health. These concerns have led to an increasing discussion in both the US and Europe about possible regulatory policies for NPM. In this article a comparative study of stakeholders’ perceptions on regulatory policy issues with NPM in Europe is presented. It was found that industry wants to regulate this area if the scientific evidence demonstrates that NPM are harmful, but also that the regulatory bodies do not find it necessary at this point of time to regulate until scientific evidence demonstrates that NPM are harmful. This research therefore shows that there will most likely not be any regulatory interventions until there is an established and convincing scientific knowledge base demonstrating that NPM can be hazardous. It is furthermore discussed in this article the different roles and responsibilities of the stakeholders in financing the research required to establish the necessary level of fundamental scientific evidence. It was also found that the activity of the regulatory bodies on this issue differ between the European countries.     

On weak convergence to Brownian motion

Summary We consider a minimal form of the usual conditions for the dependent central limit theorem and invariance principle for near martingales. We show that these conditions imply convergence to Brownian motion in a way that is slightly stronger than weak convergence in D[0,). On the other hand, if a sequence of processes with paths in D[0,) converges to Brownian motion in this way, then we can always find a sequence of partitions of the time axis that is such that these conditions hold for the corresponding array of increments.     

Quantum Mechanics from Focusing and Symmetry

A foundation of quantum mechanics based on the concepts of focusing and symmetry is proposed. Focusing is connected to c-variables—inaccessible conceptually derived variables; several examples of such variables are given. The focus is then on a maximal accessible parameter, a function of the common c-variable. Symmetry is introduced via a group acting on the c-variable. From this, the Hilbert space is constructed and state vectors and operators are given a definite interpretation. The Born formula is proved from weak assumptions, and from this the usual rules of quantum mechanics are derived. Several paradoxes and other issues of quantum theory are discussed.     

Quantum Mechanics from Symmetry and Statistical Modeling

Quantum theory is derived from a set ofplausible assumptions related to the following generalsetting: For a given system there is a set ofexperiments that can be performed, and for each suchexperiment an ordinary statistical model is defined. Theparameters of the single experiments are functions of ahyperparameter which defines the state of the system.There is a symmetry group acting on the hyperparameters, and for the induced action on the parameters ofthe single experiment a simple consistency property isassumed, called permissibility of the parametricfunction. The other assumptions needed are rather weak. The derivation relies partly on quantumlogic, partly on a group representation of thehyperparameter group, where the invariant spaces areshown to be in 1-1 correspondence with the equivalenceclasses of permissible parametric functions. Planck'sconstant only plays a role connected to generators ofunitary group representations.     

A FILTER BINDING ASSAY FOR CHARACTERIZATION OF ANTIBODIES TOWARDS DAMAGED DNA

A nitrocellulose filter binding assay was used to characterize rabbit antibodies specific for UV-irradiated DNA. The dissociation constant for the UV-DNA-antibody complex was found to be 4.2 × 10⁻¹² M. No significant binding to unirradiated DNA was observed. Unlabelled single-stranded and double-stranded DNA competed with equal efficiency for the radioactively labelled antigen (UV-irradiated φX174 DNA). The antibodies also bound to OsO₄-treated DNA, suggesting that these polyclonal antibodies also recognize minor photoproducts. Caffeine efficiently decreased binding of the antibodies to UV-irradiated DNA.     

Reduced band gap dithieno[3,2-b:2',3'-d]pyrroles: new n-type organic materials via unexpected reactivity

Direct addition of tetracyanoethylene to N-(p-hexylphenyl)dithieno[3,2-b:2',3'-d]pyrrole yields not only the aromatic mono- and bis-tricyanovinyl-substituted products but also a quinoidal product with dicyanomethylene groups. The analogous reaction with dithieno[3,2-b:2',3'-d]thiophene yields exclusively the aromatic mono-tricyanovinyl product. The aromatic and quinoidal products possess red-shifted absorptions, increased electron affinities, and favorable pi-stacking motifs in comparison to the unsubstituted oligomers.