ITC-based kinetics assay for NIS synthetases.

NIS Synthetases are a widely distributed, novel superfamily of enzymes critical to stealth siderophore production-small molecules increasingly associated with virulence. Study of these enzymes for inhibition or utilization in biosynthesis of new antibiotics has been hindered by multiple kinetics assays utilizing different limiting reporters or relying on product dissociation as a precursor to signal. We present a label free, continuous readout assay optimized for NIS Synthetase systems utilizing an isothermal titration calorimetry instrument.

Chemoenzymatic Synthesis of Select Intermediates and Natural Products of the Desferrioxamine E Siderophore Pathway.

The NIS synthetase family of enzymes responsible for the biosynthesis of siderophores is increasingly associated with bacterial virulence. Proteins in this class represent outstanding potential drug targets, assuming that basic biochemical and structural characterizations can be completed. Towards this goal, we have mated an improved synthesis of the non-commercial amino acid -hydroxy--succinylcadaverine (HSC, ) with an isothermal titration calorimetry (ITC) assay that profiles the iterative stages of HSC trimerization and macrocyclization by NIS synthetase DesD from .

Transport threshold in a quantum model for the KscA ion channel.

The mechanism behind the high throughput rate in Kchannels is still an open problem. However, recent simulations have shown that the passage of potassium through the Kchannel core, the so-called selectivity filter (SF), is water-free against models where the strength of Coulomb repulsion freezes ions conduction. Thus, it has been suggested that coherent quantum hopping might be relevant in mediating ion conduction.

Sex-Specific Differences of Steroid Receptors Following Exposure to Environmentally Relevant Concentrations of Phenothiazine in Fundulus heteroclitus.

Phenothiazine (PTZ) is a heterocyclic thiazine compound used for industrial and medical purposes. Through environmental surveillance studies, PTZ was found being discharged into a local river in Connecticut. Phenothiazine has been shown to act similarly to endocrine disrupting chemicals.

Coulomb interaction rules timescales in potassium ion channel tunneling.

Assuming the selectivity filter of KcsA potassium ion channel may exhibit quantum coherence, we extend a previous model by Vaziri and Plenio (2010 New J. Phys. 12 085001) to take into account Coulomb repulsion between potassium ions.

Low-Lying Isomers of Free-Space Halogen Clusters with Tetrahedral and Octahedral Symmetry in Relation to Stable Molecules Such as SF6.

Motivated by previous work involving one of us (N.H.M.

Second-order Møller-Plesset calculations of total ground-state energies of tetrahedral and octahedral molecules at equilibrium, confronted with some model-dependent scaling properties.

Using second-order Møller-Plesset (MP2) optimized geometries, calculations of total energies of some 20 tetrahedral and octahedral molecules have been carried out. We have then confronted these first-principles results, which of course include a fraction of the electronic correlation energy, with some model-dependent scaling properties. In particular, one scaling relation emerging from the semiclassical Thomas-Fermi electron density method relates the known nuclear-nuclear potential energy, V(nn), at equilibrium to the electron-nuclear term, V(en), and the total kinetic energy.

Exact integral constraint requiring only the ground-state electron density as input on the exchange-correlation force - partial differential(V)(xc)(r)/partial differential(r) for spherical atoms.

Following some studies of integral(n)(r)inverted DeltaV(r)dr by earlier workers for the density functional theory (DFT) one-body potential V(r) generating the exact ground-state density, we consider here the special case of spherical atoms. The starting point is the differential virial theorem, which is used, as well as the Hiller-Sucher-Feinberg [Phys. Rev.

Statistical correlations in an ideal gas of particles obeying fractional exclusion statistics.

After a brief discussion of the concepts of fractional exchange and fractional exclusion statistics, we report partly analytical and partly numerical results on thermodynamic properties of assemblies of particles obeying fractional exclusion statistics. The effect of dimensionality is one focal point, the ratio mu/k_(B)T of chemical potential to thermal energy being obtained numerically as a function of a scaled particle density. Pair correlation functions are also presented as a function of the statistical parameter, with Friedel oscillations developing close to the fermion limit, for sufficiently large density.

Optimized geometry of the cluster Gd2O3 and proposed antiferromagnetic alignment of f-electron magnetic moment.

There is currently experimental interest in assemblies of Gd2O3 clusters. This has motivated the present study in which a single such cluster in free space is examined quantitatively by spin-density functional theory, with appropriate relativistic corrections incorporated for Gd. First, the nuclear geometry of the cluster is optimized, and it is found to be such that the two Gd atoms lie in a symmetry axis perpendicular to the isosceles triangle formed by the O atoms.

Structural corrections to Stokes-Einstein relation for liquid metals near freezing.

Using recent progress relating the self-diffusion coefficient to excess entropy, structural corrections to the Stokes-Einstein relation are proposed for liquid metals near the melting temperature.

Differential virial theorem in relation to a sum rule for the exchange-correlation force in density-functional theory.

Holas and March [Phys. Rev. A.

Compressibility and specific heats of heavier condensed rare gases near the liquid-vapor critical point.

This study concerns the way to describe some physical properties of simple liquids by using the Bogoliubov-Born-Green-Kirkwood-Yvon hierarchy. It constructively analyzes the recent contribution of Sarkisov [G. N.

Equilibrium geometries of low-lying isomers of some Li clusters, within Hartree-Fock theory plus bond order or MP2 correlation corrections.

In a recent study by Kornath et al. [J. Chem.

Topology, connectivity, and electronic structure of C and B cages and the corresponding nanotubes.

After a brief discussion of the structural trends which appear with an increasing number of atoms in B cages, a one-to one correspondence between the connectivity of B cages and C cage structures will be proposed. The electronic level spectra of both systems from Hartree-Fock calculations is given and discussed. The relation of curvature introduced into an originally planar graphitic fragment to pentagonal "defects" such as are present in buckminsterfullerene is also briefly treated.

Relation between transport and thermodynamic properties in liquid sp-electron metals near freezing.

Classical statistical mechanics based on assumed pair potentials leads, for liquid metals, to an approximate relation between shear viscosity eta, surface tension sigma, and thermal velocity vT defined as (kBT/M)(1/2), with M the ionic mass. Theory predicts for the dimensionless grouping sigma/etav(T) evaluated at the melting temperature Tm a single value 15 / 16; liquid sp-electron metals exhibit, however, a scatter from around 0.7 to 2.

Generalized Stokes-Einstein relation for liquid metals near freezing.

Deviations from a Stokes-Einstein relation between the self-diffusion coefficient D and shear viscosity eta for liquid metals near freezing are shown to correlate with a net transit parameter xi introduced recently by Wallace [Phys. Rev. E 58, 538 (1998)] in a two-parameter model of D.

Many-body partition function and thermal hartree-fock approximations.

The hierarchy equations for the quantum thermal density matrices of an assembly of interacting particles in an external potential are derived in a compact form. This approach can complement and finally replace the phenomenological treatment of the thermodynamic properties of quantum gasses, liquids, and solids. We also derive a temperature Hartree-Fock approximation for fermions based on the symmetry properties of the exact hierarchy and finally we discuss the present approximation in relation to that of Kaplan and Argyres [T.