A unique geometry of the active site of angiotensin-converting enzyme consistent with structure-activity studies

Summary Previous structure-activity studies of captopril and related active angiotensin-converting enzyme (ACE) inhibitors have led to the conclusion that the basic structural requirements for inhibition of ACE involve (a) a terminal carboxyl group; (b) an amido carbonyl group; and (c) different types of effective zinc (Zn) ligand functional groups. Such structural requirements common to a set of compounds acting at the same receptor have been used to define a pharmacophoric pattern of atoms or groups of atoms mutually oriented in space that is necessary for ACE inhibition from a stereochemical point of view. A unique pharmacophore model (within the resolution of approximately 0.15 Å) was observed using a method for systematic search of the conformational hyperspace available to the 28 structurally different molecules under study. The method does not assume a common molecular framework, and, therefore, allows comparison of different compounds that is independent of their absolute orientation.Consequently, by placing the carboxyl binding group, the binding site for amido carbonyl, and the Zn atom site in positions determined by ideal binding geometry with the inhibitors' functional groups, it was possible to clearly specify a geometry for the active site of ACE.     

Magnetic field effects on the optical properties of an azo-dye doped liquid crystal

Homeotropically aligned nematic liquid crystals doped with azo-dye were subjected both to a linear polarized light of a He–Ne laser and to a magnetic field perpendicular to the incident light beam. We found that the emerging light was elliptically polarized when using magnetic field strengths higher than the threshold value for the magnetic Freedericksz transition. The light transmission, the rotatory power (induced by azo-dye) and the ellipticity varied quasiperiodically when increasing magnetic field strength. The number and positions of maxima and minima depend on the cell thicknesses. Changes in the phase difference between the emergent ordinary and extraordinary rays were computed from the experimental data and the magnetic field dependence of the birefringence was determined.     

Mesomorphic Properties of Some Sitosteryl Esters

The mesomorphic properties of some esters formed by aromatic acids with β-sitosterol are reported. It is shown that para-substituted benzoates are compounds exhibiting enantiotropic cholesteric and some smectic mesophases. Connections between the clearing points of sitosteryl esters and their homologous cholesteryl derivatives are discussed.     

Das Monte Carlo-studium der copolymerisation der ester der benzylidencyanessigsäure mit styrol

The Monte Carlo study of copolymerization of styrene with four esters of benzylidenecyanoacetic acid has pointed out that (a) for methyl and hexyl esters one cannot decide among the ultimate and penultimate effect (using copolymer composition and Fischer statistic), and (b) cyclohexyl and benzyl esters copolymerize following the kinetics of penultimate effect. Finally, the most probable sequence distribution in the studied copolymers is presented.     

Growth Kinetics of Cholesteric Spherulites Under Electric Fields

The growth kinetics of cholesteric spherulites of cholesteryl laurate-cholesteryl caprilate mixture (50: 50% by weight) is investigated. It is show that the nucleation is bidimensional and the growth is determined by the orientational relaxation of the molecules near the interface. The same growth mechanism holds when the nucleation was followed under d.c. electric fields; in this case the growth rates were lower.

The electric field effects on growth kinetics can be explained by considering both changes in critical supersaturation and changes in some coefficients associated with dissipative effects during relaxation.     

Thermal expansivity and degradation properties of PLA/HA and PLA/βTCP in vitro conditioned composites

Journal of Thermal Analysis and Calorimetry - The objective of this study was to investigate the thermal expansivities and degradation properties for several in vitro conditioned biodegradable...     

Topological effect on mo energies: On the MO energies of topologically related benzoquinones

Non-empirical HF SCF MO calculations have been performed for the topologically related o-and p-benzoquinones. The SCF π-MO eigenvalues obtain     

Orbital electronegativity and analytical representation of atom valence state energy

An analytical representation of atom valence state energy (E(n_j), j = 1,…?4; E(n_j) is a nonlinear function of orbital occupancy numbers n_j) is proposed and explicitly derived for H? Ar; the values of electronegativity calculated based on E(n_j) agree within truncation error with those of Hinze and Jaffe. However, in our representation, orbital electronegativity χ and hardness parameters η of a given orbital always include nonlinear contributions from other orbitals, hence accounting for their influence on χ and η. An atomic charge calculation procedure based on E(n_j) is also described and shown to perform well.     

Coefficient of thermal expansion evolution for cryogenic preconditioned hybrid carbon fiber/glass fiber-reinforced polymeric composite materials

Polymeric matrix composites are susceptible to degradation and material properties changes if subjected to low-temperature environmental conditions. This paper attempts to present a study on effective coefficient of thermal expansion for various hybrid carbon fibers/glass fibers polymeric composite structures previously subjected to low-temperature environmental conditioning. The hybrid composite architectures were made from various layers of glass mat and/or glass woven embedded along with layers of unidirectional carbon fibers into a polymeric matrix. The samples were preconditioned to a low-temperature environment at a constant temperature of ?35 °C for 1-week long, 24 h/day. The instantaneous CTE and thermal strain fields were recorded with a DIL 402 PC/1 dilatometer from Netzsch GmbH (Germany) by setting a monotonically linear rise of temperature from 20 to 250 °C, at a rate of 1 °C min^?1. The experimentally retrieved data were compared with the values obtained by running a micromechanical-based approach simulation on a representative volume element.