Chavicol formation in sweet basil (Ocimum basilicum): cleavage of an esterified C9 hydroxyl group with NAD(P)H-dependent reduction

Propenyl- and allyl-phenols, such as methylchavicol, p-anol and eugenol, have gained importance as flavoring agents and also as putative precursors in the biosynthesis of 9,9'-deoxygenated lignans, many of which have potential medicinal applications. In spite of several decades of investigation, however, the complete biosynthetic pathway to a propenyl/allylphenol had not yet been reported. We have subjected a Thai basil variety accumulating relatively large amounts of the simplest volatile allylphenol, methylchavicol, to in vivo administration of radiolabeled precursors and assays of protein preparations in vitro. Through these experiments, the biosynthesis of chavicol was shown to occur via the phenylpropanoid pathway to p-coumaryl alcohol. Various possibilities leading to deoxygenation of the latter were examined, including reduction of the side-chain double bond to form p-dihydrocoumaryl alcohol, followed by dehydration to afford chavicol, as well as formation of p-methoxycinnamyl alcohol, with further side-chain modification to afford methylchavicol. A third possibility studied was activation of the side-chain alcohol of p-coumaryl alcohol, e.g.via esterification, to form a more facile leaving group via reductive elimination. The latter was shown to be the case using p-coumaryl esters as potential substrates for a NAD(P)H-dependent reductase to afford chavicol, which is then O-methylated to afford methylchavicol.     

Adiabatic pumping in interacting systems

A dc current can be pumped through an interacting system by periodically varying two independent parameters such as the magnetic field and a gate potential. We present a general expression for the adiabatic pumping current in interacting systems, written in terms of instantaneous properties of the system at equilibrium, and find the limits of its applicability. This expression generalizes the scattering approach for noninteracting particles. We apply our formula for a quantum critical system that exhibits the two-channel Kondo effect, where single particle excitations are not well defined. We find that if the quantum critical point is contained in the pumping trajectory, the pumped spin between the channels approaches h, and if it is not contained in the trajectory, the spin approaches zero when the temperature T --> 0. We discuss the non-Fermi liquid features of this system at finite T.     

Self-assembly of nanoparticles into rings: a lattice-gas model

A coarse-grained lattice-gas model in three dimensions is developed to study the self-assembly of nanoparticles into micrometer-sized rings from a thin liquid film containing the nanoparticles. The model describes the nanoparticles as well as the solvent on length scales that are typical of the solvent bulk correlation length. Morphologies obtained from simulations of the model resemble recent experiments and provide a microscopic picture for the formation of nanoparticle rings. The role of evaporation rate, film thickness, diffusion rate, and nanoparticle coverage is discussed and compared to other continuum theories. Predictions of novel structures resulting from low nanoparticle mobility are analyzed.     

Nonpolytopal Nonsimplicial Lattice Spheres with Nonnegative Toric g-Vector

We construct many nonpolytopal nonsimplicial Gorenstein^? meet semi-lattices with nonnegative toric g-vector, supporting a conjecture of Stanley. These are formed as Bier spheres over the face posets of multiplexes, polytopes constructed by Bisztriczky as generalizations of simplices.     

On vanishing patterns in <Emphasis Type="Italic">j</Emphasis>-strands of edge ideals

We consider two problems regarding vanishing patterns in the Betti table of edge ideals I over any fixed field. First, we show that the j-strand is connected if \(j=3\) (for \(j=2\) this is easy and known), and give examples where the j-strand is not connected for any \(j>3\). Next, we apply our result on strand connectivity to establish the subadditivity conjecture for edge ideals, \(t_{a+b}(I)\le t_a(I)+t_b(I)\), in case \(b=2,3\) (the case \(b=1\) is known). Here \(t_i(I)\) denote the maximal shifts in the minimal free resolution of S / I over its polynomial algebra.     

H2S Removal from Groundwater by Chemical Free Advanced Oxidation Process Using UV-C/VUV Radiation

Sulfide species may be present in groundwater due to natural processes or due to anthropogenic activity. H₂S contamination poses odor nuisance and may also lead to adverse health effects. Advanced oxidation processes (AOPs) are considered promising treatments for hydrogen-sulfide removal from water, but conventional AOPs usually require continuous chemical dosing, as well as post-treatment, when solid catalysts are applied. Vacuum-UV (VUV) radiation can generate ·OH in situ via water photolysis, initiating chemical-free AOP. The present study investigated the applicability of VUV-based AOP for removal of H₂S both in synthetic solutions and in real groundwater, comparing combined UV-C/VUV and UV-C only radiation in a continuous-flow reactor. In deionized water, H₂S degradation was much faster under the combined radiation, dominated by indirect photolysis, and indicated the formation of sulfite intermediates that convert to sulfate at high radiation doses. Sulfide was efficiently removed from natural groundwater by the two examined lamps, with no clear preference between them. However, in anoxic conditions, common in sulfide-containing groundwater, a small advantage for the combined lamp was observed. These results demonstrate the potential of utilizing VUV-based AOP for treating H₂S contamination in groundwater as a chemical-free treatment, which can be especially attractive to remote small treatment facilities.     

Experimental study of shape transitions and energy scaling in thin non-Euclidean plates

We present the first quantitative measurements of shape and energy variation in non-Euclidean plates. Using environmentally responsive gel, we construct non-Euclidean disks of constant imposed Gaussian curvature, K(tar). We vary the disks' thickness t(0) and measure the dependence of configurations, surface curvature, and energy content on t(0). For K(tar)<0, configurations are of a single wavy mode and undergo a set of bifurcations that leads to their refinement with decreasing thickness. This leads to sharp increase in the amount of surface bending as t(0)→0, and to a slow decay of both bending and stretching energies. Both vary like t(0)(2), compared with t(0)(3) of the bending energy in disks with K(tar)>0.     

Linear response theory for hard and soft glassy materials

Despite qualitative differences in their underlying physics, both hard and soft glassy materials exhibit almost identical linear rheological behaviors. We show that these nearly universal properties emerge naturally in a shear-transformation-zone theory of amorphous plasticity, extended to include a broad distribution of internal thermal-activation barriers. The principal features of this barrier-height distribution are predicted by nonequilibrium, effective-temperature thermodynamics. Our theoretical loss modulus G'(ω) has a peak at the α relaxation rate, and a power law decay of the form ω(-ζ) for higher frequencies, in quantitative agreement with experimental data.