Solubility of climbazole and triclocarban in supercritical carbon dioxide: Measurement and correlation

The supercritical technology has been considered as an appropriate alternative for separation of biomaterials from cosmetic, food, and pharmaceutical products. The solid solubility of biological compounds is the most important thermodynamic parameter in the supercritical extraction and purification. The equilibrium solubility of two biocides, climbazole, and triclocarban was measured in supercritical carbon dioxide with static method in the pressure range from (10 to 40) MPa and at temperatures equal to (313.2, 323.2, and 333.2) K. The experimental data were correlated by Peng–Robinson equation of state and quasi-chemical nonrandom lattice fluid model.     

Synthesis, improved antisense activity and structural rationale for the divergent RNA affinities of 3'-fluoro hexitol nucleic acid (FHNA and Ara-FHNA) modified oligonucleotides

The synthesis, biophysical, structural, and biological properties of both isomers of 3'-fluoro hexitol nucleic acid (FHNA and Ara-FHNA) modified oligonucleotides are reported. Synthesis of the FHNA and Ara-FHNA thymine phosphoramidites was efficiently accomplished starting from known sugar precursors. Optimal RNA affinities were observed with a 3'-fluorine atom and nucleobase in a trans-diaxial orientation. The Ara-FHNA analog with an equatorial fluorine was found to be destabilizing. However, the magnitude of destabilization was sequence-dependent. Thus, the loss of stability is sharply reduced when Ara-FHNA residues were inserted at pyrimidine-purine (Py-Pu) steps compared to placement within a stretch of pyrimidines (Py-Py). Crystal structures of A-type DNA duplexes modified with either monomer provide a rationalization for the opposing stability effects and point to a steric origin of the destabilization caused by the Ara-FHNA analog. The sequence dependent effect can be explained by the formation of an internucleotide C-F···H-C pseudo hydrogen bond between F3' of Ara-FHNA and C8-H of the nucleobase from the 3'-adjacent adenosine that is absent at Py-Py steps. In animal experiments, FHNA-modified antisense oligonucleotides formulated in saline showed a potent downregulation of gene expression in liver tissue without producing hepatotoxicity. Our data establish FHNA as a useful modification for antisense therapeutics and also confirm the stabilizing influence of F(Py)···H-C(Pu) pseudo hydrogen bonds in nucleic acid structures.     

Deracemization of unnatural amino acid: homoalanine using D-amino acid oxidase and ω-transaminase

A deracemization method was developed to generate optically pure L-homoalanine from racemic homoalanine using D-amino acid oxidase and ω-transaminase. A whole cell reaction using a biphasic system converted 500 mM racemic homoalanine to 485 mM L-homoalanine (>99% ee).     

Homology of Littlewood complexes

Let $V$ be a symplectic vector space of dimension $2n$ . Given a partition $\lambda $ with at most $n$ parts, there is an associated irreducible representation $\mathbf{{S}}_{[\lambda ]}(V)$ of $\mathbf{{Sp}}(V)$ . This representation admits a resolution by a natural complex $L^{\lambda }_{\bullet }$ , which we call the Littlewood complex, whose terms are restrictions of representations of $\mathbf{{GL}}(V)$ . When $\lambda $ has more than $n$ parts, the representation $\mathbf{{S}}_{[\lambda ]}(V)$ is not defined, but the Littlewood complex $L^{\lambda }_{\bullet }$ still makes sense. The purpose of this paper is to compute its homology. We find that either $L^{\lambda }_{\bullet }$ is acyclic or it has a unique nonzero homology group, which forms an irreducible representation of $\mathbf{{Sp}}(V)$ . The nonzero homology group, if it exists, can be computed by a rule reminiscent of that occurring in the Borel–Weil–Bott theorem. This result can be interpreted as the computation of the “derived specialization” of irreducible representations of $\mathbf{{Sp}}(\infty )$ and as such categorifies earlier results of Koike–Terada on universal character rings. We prove analogous results for orthogonal and general linear groups. Along the way, we will see two topics from commutative algebra: the minimal free resolutions of determinantal ideals and Koszul homology.     

Oxygen-pressure dependence of the crystallinity of MgO films grown on Si(1 0 0) by PLD

Effects of the oxygen partial pressure on pulsed-laser deposition of MgO buffer layers on silicon substrates were investigated. The overall growth process was monitored in situ by reflection high-energy electron diffraction (RHEED) method. It was found that the crystallinity and surface morphology of the MgO films were strongly affected by oxygen partial pressure in the deposition chamber. The oxygen-pressure dependence could be explained in terms of interactions of oxygen with species in the plume-like plasma. The MgO film obtained at an optimal oxygen-pressure range of 1×10⁻²–1 Pa exhibited an atomic-smooth and defect-free surface (the root-mean-square roughness being as low as 0.82 nm). For the metal–insulator–metal (MIM) structure of Au/MgO (150 nm)/TiN prepared at the optimal growth conditions achieved a very low leak current density of 10⁻⁷ A cm⁻² at an electric field of 8×10⁵ V cm⁻¹ and the permittivity (ε_r) of about 10.6, virtually the same as that of the bulk MgO single crystals.     

Can the replacement of a single atom in the enzyme horseradish peroxidase convert it into a monoxygenase? A density functional study

Density functional calculations on horseradish peroxidase mutants are presented, whereby one or two of the nitrogen atoms of the axial histidine ligand have been replaced by phosphorus atoms. Our calculations show that phosphorus entices a push effect on the oxoiron group, whereas a histidine side chain withdraws electrons. As a result, we predict that a phosphorus-substituted histidine ligand will convert the active form of a peroxidase into a monoxygenase. This subsitution may be useful for the bioengineering of commercially exploitable enzymes.     

Comparison of linear and 2D IR spectra in the presence of fast exchange

The few picosecond time scale H-bond making and breaking in the system acetonitrile-methanol dominates the mechanism of vibrational coherence transfer that is evident in the shapes of both the linear and nonlinear IR spectra of the CN group.     

Structural and morphological study of ZnO thin films electrodeposited on n-type silicon

In this work, we report on the electrodeposition of ZnO thin films on n-Si (1 0 0) and glass substrates. The influence of the deposition time on the morphology of ZnO thin films was investigated. The ZnO thin films were characterized by X-ray diffraction (XRD), energy dispersive X-ray (EDS) and scanning electron microscopy (SEM). The results show a variation of ZnO texture from main (0 0 2) at 10 min to totally (1 0 1) at 15 min deposition time. The photoluminescence (PL) studies show that both UV (∼382 nm) and blue (∼432 nm) luminescences are the main emissions for the electrodeposited ZnO films. In addition, the film grown at 15 min indicates an evident decrease of the yellow-green (∼520 nm) emission band comparing with that of 10 min. Finally, transmittance spectra show a high transmission value up to 85% in the visible wavelength range. Such results would be very interesting for solar cells applications.     

A space-indexed formulation of packing boxes into a larger box

Current integer programming solvers fail to decide whether 12 unit cubes can be packed into a 1×1×11 box within an hour using the natural relaxation of Chen/Padberg. We present an alternative relaxation of the problem of packing boxes into a larger box, which makes it possible to solve much larger instances.     

Non-extinction of a Fleming-Viot particle model

We consider a branching particle model in which particles move inside a Euclidean domain according to the following rules. The particles move as independent Brownian motions until one of them hits the boundary. This particle is killed but another randomly chosen particle branches into two particles, to keep the population size constant. We prove that the particle population does not approach the boundary simultaneously in a finite time in some Lipschitz domains. This is used to prove a limit theorem for the empirical distribution of the particle family.