IR-induced processes for allyl alcohol dimers involving an intermolecular OH...π Bond in low-temperature matrices

Sharp peaks were observed in the IR spectra of allyl alcohol dimers in the νOH and τOH regions in low-temperature Ar and N₂ matrices. In Ar a peak at 3587 cm^?1 was found to increase in intensity upon annealing and decrease upon IR irradiation; it is concluded that this peak is due to an OH...π interaction (of a cyclic structure) present in part of the dimers. This is the first time such an interaction and photoprocess have been found for an alcohol in matrices. Also a faster photo-process was found. Confomer changes in the monomers accompany the photoprocess in allyl alcohol dimers.     

Levi-parallel contact Riemannian manifolds

We study the Riemannian geometry of contact manifolds with respect to a fixed admissible metric, making the Reeb vector field unitary and orthogonal to the contact distribution, under the assumption that the Levi–Tanaka form is parallel with respect to a canonical connection with torsion.     

A one-dimensional model with water-like anomalies and two phase transitions

We investigate a one-dimensional model that shows several properties of water. The model combines the long-range attraction of the van der Waals model with the nearest-neighbor interaction potential by Ben-Naim, which is a step potential that includes a hard core and a potential well. Starting from the analytical expression for the partition function, we determine numerically the Gibbs energy and other thermodynamic quantities. The model shows two phase transitions, which can be interpreted as the liquid-gas transition and a transition between a high-density and a low-density liquid. At zero temperature, the low-density liquid goes into the crystalline phase. Furthermore, we find several anomalies that are considered characteristic for water. We explore a wide range of pressure and temperature values and the dependence of the results on the depth and width of the potential well.     

Production of milligram quantities of affinity tagged-proteins using automated multistep chromatographic purification

A new chromatography system, AKTAxpress (GE Healthcare, Amersham Biosciences, Uppsala, Sweden) has been designed to meet the demand for high-throughput purification of proteins in structural genomics and drug discovery. The system offers a number of automated multistep purification protocols for affinity-tagged proteins. All protocols start with affinity chromatography followed by combinations of desalting, ion exchange chromatography and gel filtration. As an option, tag removal can be included in the purification protocols. Up to 16 proteins can be purified per day and the yield can be as high as 50 mg of each protein at > 90% purity. To highlight the versatility of the system, this paper presents several case studies; purifications of hexahistidine- and glutathione S-transferase-tagged proteins using different protocols, automated on-column tag cleavage and optimization studies for a hexahistidine-tagged kinase.     

Synthesis of multi ring-fused 2-pyridones via an acyl-ketene imine cyclocondensation

[STRUCTURE: SEE TEXT] Polycyclic ring-fused 2-pyridones (5a-e and 9a-e) have been prepared via a microwave-assisted acyl-ketene imine cyclocondensation. Starting from 3,4-dihydroisoquinolines (4a-b) or 3,4-dihydroharman (8), fused 2-pyridones could be prepared in a one-step procedure. By using either Meldrum's acid derivatives (1a-d) or 1,3-dioxine-4-ones (7a-b) as acyl-ketene sources, mono- or disubstitution of the fused 2-pyridone ring could be accomplished. As an application of the method, a formal synthesis of the indole alkaloid sempervilam was performed.     

Foliations of the Sasakian Space R2n+1 by Minimal Slant Submanifolds

Examples of slant submanifolds in the Sasakian space R²ⁿ⁺¹ are obtained as the leaves of a harmonic, Riemannian 3-dimensional foliation. With the exception of the anti-invariant ones, these leaves are all locally homogeneous manifolds with negative scalar curvature, whose Ricci tensor satisfies (S)(X, X) = 0 for all tangent vector fields.     

Fast and selective synthesis of novel cyclic sulfamide HIV-1 protease inhibitors under controlled microwave heating

A novel and highly selective silver-promoted monobenzylation method was developed to promote synthesis of nonsymmetrical sulfamide-based HIV-1 inhibitors. Microwave-accelerated palladium-catalyzed N-amide arylation- and aminocarbonylation reactions were employed for rapid and reliable compound generation. With this class of inhibitory agents, six active inhibitors were identified, the most potent inhibitor possessing a K_i-value of 20 nM.