Thermodynamics of peptide dimer formation

The Replica Exchange Statistical Temperature Molecular Dynamics algorithm is used to study the equilibrium properties of a peptide monomer and dimer and the thermodynamics of peptide dimer formation. The simulation data are analyzed by the Statistical Temperature Weighted Histogram Analysis Method. Each 10-residue peptide is represented by a coarse-grained model with hydrophobic side chains and has an α-helix as its minimum energy configuration. It is shown that the configurational behavior of the dimer can be divided into four regions as the temperature increases: two folded peptides; one folded and one unfolded peptide; two unfolded peptides; and two spatially separated peptides. Two important phenomena are discussed: in the dimer, one peptide unfolds at a lower temperature than the isolated monomer and the other peptide unfolds at a higher temperature than the isolated monomer. In addition, in the temperature region where one peptide is folded and the other unfolded, the unfolded peptide adopts an extended structure that minimizes the overall surface area of the aggregate. It is suggested that combination of destabilization due to aggregation and the resulting extended configuration of the destabilized peptide could have implications for nucleating β-sheet structures and the ultimate formation of fibrils.     

High-performance liquid chromatographic determination of ganciclovir in plasma.

A rapid, selective and sensitive isocratic reversed-phase high-performance liquid chromatographic method for the determination of ganciclovir in plasma samples was developed. This method, which was applied to the analysis of plasma ganciclovir from heart transplant patients under ganciclovir therapy for cytomegalovirus infections, represents a suitable analytical tool for drug monitoring and pharmacokinetic investigations.     

What mesoscopic structures really “remember”: insufficiency of the open boundary approximation

We analyze the influence of contact electrons on quantum transport in a resonant-tunneling diode (RTD), using a many-body density matrix formalism for open systems. We explicitly relate the net current in the RTD to the memory-containing effective interaction between the RTD active region and the contacts. This effect can only be captured if the RTD active region is treated fully as a dynamically open system.     

From fluoral to heterocycles: a survey of polyfluorinated iminiums chemistry

Hemiaminals of fluorinated aldehydes are very useful reagents. They are able, under Lewis acid activation, to generate iminium species which can react with various nucleophiles and provide diverse fluorinated compounds. By this methodology, β-fluoroalkylated enones, which are very interesting building blocks, have been easily obtained. Fluorinated homoallylamines have been also synthesized and used as starting material to prepare α-fluoroalkylated nitrogen heterocycles. Many other synthetic applications of these fluorinated iminium ions provide new bioactive compounds.     

Silica Films Containing Ordered Pores Prepared by Dip Coating of Silica Nanoparticles and Polystyrene Beads Colloidal Mixture

Silica films containing three dimensionally (3D) ordered pores were prepared by a simple dip coating method. A colloidal sol containing silica particles in the nanometer size range and a polystyrene latex (PSL) colloidal sol containing particles of tens of nanometers to one micrometer in size were used as precursors. The pore periodicity, which in turn produces the dielectric periodicity, can be easily altered by changing the size of the PSL beads. Films having a high surface smoothness were obtained by using small silica particles, large PSL particles, and a low withdrawal speed in the dip-coating. When the films were irradiated with a white light source, the reflective spectrum was changed by varying the incident angle, indicating its possible use as a monochromator. The change in the reflective spectrum was explained using effective medium approximation combined with a simple Bragg reflection equation.