Molecular Modeling to Estimate the Diffusion Coefficients of Drugs and Other Small Molecules.

Diffusion is a spontaneous process and one of the physicochemical phenomena responsible for molecular transport, the rate of which is governed mainly by the diffusion coefficient; however, few coefficients are available because the measurement of diffusion rates is not straightforward. The translational diffusion coefficient is related by the Stokes-Einstein equation to the approximate radius of the diffusing molecule. Therefore, the stable conformations of small molecules were first calculated by molecular modeling. A simple radius rs and an effective radius re were then proposed and estimated using the stable conformers with the van der Waals radii of atoms. The diffusion coefficients were finally calculated with the Stokes-Einstein equation. The results showed that, for the molecules with strong hydration ability, the diffusion coefficients are best given by re and for other compounds, rs provided the best coefficients, with a reasonably small deviation of ~0.3 × 10-6 cm2/s from the experimental data. This demonstrates the effectiveness of the theoretical estimation approach, suggesting that diffusion coefficients have potential use as an additional molecular property in drug screening.

Changes to fine structure, size and mechanical modulus of phytoglycogen nanoparticles subjected to high-shear extrusion.

This study aims to enhance the understanding of the structure of maize phytoglycogen nanoparticles, and the effect of shear scission on their architecture, radius, stiffness, and deformability. Compared to amylopectin, phytoglycogen had a lower A:B chain ratio, a lower number of chains per B chain, and a much higher number of Afingerprint chains. Phytoglycogen (Mw = 28.0 × 106 g/mol) was subjected to high-shear extrusion with varying Specific Mechanical Energies (SMEs) using different screw speeds, showing a maximum stable molecular weight Mw of ∼9.31 × 106 g/mol and a particle radius R reduction of 36 %, with a corresponding 20 % increase in the average mass density. Atomic force microscopy force spectroscopy revealed that nanoparticles extruded at the lowest SME (122 Wh/kg) exhibited a 20 % increase in Young's modulus. Higher SME values (up to 488 Wh/kg) resulted in an overall decrease in stiffness without further significant reductions in radius.

Physical parameters of blood as a non - newtonian fluid.

Do increasing doses of electromagnetic fields (EMFs) increase the hazards effect on blood? Studies on the blood of rats provide guidance for the assessment of occupational and public health significance of exposure to EMFs. Here, apparent additive viscosity of animal blood after exposing to EMFs (3,5 and 10 gauss) is examined. The results indicate that hematocrite (HCT) increased as EMF increases while the viscocity decreased with the increase of EMF. Red blood cell permeability, deformability and the electrical properties of hemoglobin (conductivity and relaxation time) were also examined. The results show that EMF produces pronounced changes in the molecular structure of hemoglobin and induced force acting on the charged particle of charge q which may activate Rouleau formation of red blood cells (RBCs).