Four-component pharmacophore model for endomorphins toward μ opioid receptor subtypes.

In the present work, a series of simulation tools were used to determine structure-activity relationships for the endomorphins (EMs) and derive μ-pharmacophore models for these peptides. Potential lowest energy conformations were determined in vacuo by systematically varying the torsional angles of the Tyr(1)-Pro(2) (ω(1)) and Pro(2)-Trp(3)/Phe(3) (ω(2)) as tuning parameters in AM1 calculations. These initial models were then exposed to aqueous conditions via molecular dynamics simulations.

On the use of hollow tube geometries for resonant ultrasound spectroscopy.

Resonant ultrasound spectroscopy (RUS) can nondestructively obtain the elastic constants of compact specimens, however many materials have hollow cross-sections and frequency analysis of such geometries is required before inclusion in the RUS methodology. Resonant mode shapes of tubes with length equal to diameter and varying ratios of tube inner to outer diameter (Λ) as well as Poisson's ratio (ν) were identified by eigenvalue analysis using a commercial finite element code. Longitudinal and shear RUS experiments were conducted on tubes with Λ varying between 0 and 0.

Resonant ultrasound spectroscopy of cylinders over the full range of Poisson's ratio.

Mode structure maps for freely vibrating cylinders over a range of Poisson's ratio, ν, are desirable for the design and interpretation of experiments using resonant ultrasound spectroscopy (RUS). The full range of isotropic ν (-1 to +0.5) is analyzed here using a finite element method to accommodate materials with a negative Poisson's ratio.