Molecular physiology of rhodopsin: Computer simulation

Computer simulation is used for comparative investigation of the molecular dynamics of rhodopsin containing the chromophore group (11-cis-retinal) and free opsin. Molecular dynamics is traced within a time interval of 3000 ps; 3 × 10⁶ discrete conformational states of rhodopsin and opsin are obtained and analyzed. It is demonstrated that the presence of the chromophore group in the chromophore center of opsin influences considerably the nearest protein environment of 11-cis-retinal both in the region of the β-ionone ring and in the region of the protonated Schiff base bond. Based on simulation results, a possible intramolecular mechanism of keeping rhodopsin as a G-protein-coupled receptor in the inactive state, i.e., the chromophore function as an efficient ligand antagonist, is discussed.     

An ultrasonic method for measuring stresses in engineering materials

A ‘multiparameter’ method for indirect evaluation of intrinsic anisotropy values for prestressed engineering materials is discussed. The proposed method is based on simultaneous measurement of both the velocity of elastic waves and the parameters, characterizing the frequency dispersion and/or attenuation. Preliminary experimental demonstrations of the feasibility of such methods for common engineering materials are presented.     

Deuterium Rotating Frame NMR Relaxation Measurements in the Solid State under Static Conditions for Quantification of Dynamics

The feasibility of static deuterium rotating frame NMR relaxation measurements for characterization of slow timescale motions in powder systems is demonstrated. Using a model compound dimethyl sulfone-d₆, we show that these measurements yield conformational exchange rates and activation energy values in accordance with results obtained with other techniques. Furthermore, we demonstrate that the full Liouvillian approach as opposed to the Redfield approximation is necessary to analyze the experimental data.     

Optical classification of random image fields using spectral synthetic discriminant functions

It is shown that the problem of classification of images that have the perfectly random nature may be solved with the help of synthetic discriminant functions being synthesized by least-squares technique to separate linearly the power spectra of the corresponding random image fields. The realization of the proposed method by means of an optical technique is discussed, and its efficiency is illustrated by two examples of real-life texture classification.     

Combined use of calorimetric and adsorption kinetic methods for the study of the mechanisms of catalytic processes

Consideration is given to the main results obtained in studies based on calorimetric methods at high temperatures (above room temperature) of the following aspects of the mechanisms of catalytic and sorption processes on powder catalysts: 1) relation between chemisorption and dissolution of gases in the subsurface layers of solids; 2) influence of surface-adsorbed substance on the adsorption of another substance from the gas phase; 3) nature of intermediate species formed during catalytic processes on the catalyst surface. Results are presented of the application of calorimetric methods to measuring the enthalpy change of polymerization in a dry system: gaseous monomer — solid catalyst — solid polymer, and to investigating the mechanisms of such processes. Anomalous solubility of gases in the subsurface layers of solids has been shown to be significant for the mechanism of nucleation during phase transitions in solids.

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Zusamenfassung Die wichtigsten Ergebnisse der auf kalorimetrischen Methoden bei hohen Temperaturen (über Raumtemperatur) beruhenden Untersuchungen der Mechanismen von katalytischen und Sorptionsprozessen an pulverförmigen Katalysatoren werden behandelt: 1) Zusammenhang zwischen Chemisorption und Lösung von Gasen in den Schichten von Festkörpern unterhalb der Oberfläche; 2) Einfluß der an der Oberfläche adsorbierten Substanz auf die Adsorption einer anderen Substanz aus der Gasphase; 3) Beschaffenheit der während des katalytischen Vorgangs an der Katalysator-Oberfläche entstandenen Intermediärteilchen.Ergebnisse der Anwendung der kalorimetrischen Methode zur Messung der Enthalpie-Änderungen der Polymerisation im trockenen System: gasförmiges Monomer — fester Katalysator — festes Polymer und zur Untersuchung der Mechanismen solcher Vorgänge werden mitgeteilt. Es wurde gezeigt, daß die anomale Löslichkeit von Gasen in den Schichten unterhalb der Oberfläche von Festkörpern für den Mechanismus der Keimbildung während des Phasenüberganges in Festkörpern von Bedeutung ist.

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Résumé On examine les principaux résultats obtenus lors des études effectuées à l'aide de méthodes calorimétriques à hautes températures (au-dessus de la température ambiante), sous les aspects suivants du mécanisme des réactions catalytiques et de Sorption sur des catalyseurs en poudre: 1) relation entre la chimisorption et la dissolution des gaz dans les sous-couches superficielles des solides, 2) influence d'une substance adsorbée en surface sur l'adsorption d'une autre substance de la phase gazeuse, 3) nature des particules intermédiaires formées lors de la réaction catalytique à la surface du catalyseur. Les résultats de l'application de la méthode calorimétrique à la mesure des variations d'enthalpie au cours de la polymérisation en système «sec» sont présentés: monomère gazeux — catalyseur solide — polymère solide, ainsi que ceux relatifs à l'étude du mécanisme de ces réactions. On montre que la solubilité anormale des gaz dans les sous-couches superficielles des solides joue un rôle important sur le mécanisme de la nucléation lors des transitions de phases dans les solides.

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Gas‐phase and liquid‐state properties of esters,nitriles, and nitro compounds with the OPLS‐AA force field

Nonbonded and torsional parameters for carboxylate esters, nitriles, and nitro compounds have been developed for the OPLS‐AA force field. In addition, torsional parameters for alkanes have been updated. These parameters were fit to reproduce ab initio gas‐phase structures and conformational energetics, experimental condensed‐phase structural and thermodynamic properties, and experimental free energies of hydration. The computed densities, heats of vaporization, and heat capacities for fifteen liquids are in excellent agreement with experimental values. The new parameters permit accurate molecular modeling of compounds containing a wider variety of functional groups, which are common in organic molecules and drugs. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1340–1352, 2001     

Generation of a secondary electromagnetic source with desired statistical properties

Two known alternative techniques for generating a secondary electromagnetic Schell-model source with the prescribed statistical properties are analyzed and compared from the point of view of their capability to provide the given degree of polarization and the desired transverse coherence length.     

Development of a Grp94 inhibitor

Heat shock protein 90 (Hsp90) represents a promising therapeutic target for the treatment of cancer and other diseases. Unfortunately, results from clinical trials have been disappointing as off-target effects and toxicities have been observed. These detriments may be a consequence of pan-Hsp90 inhibition, as all clinically evaluated Hsp90 inhibitors simultaneously disrupt all four human Hsp90 isoforms. Using a structure-based approach, we designed an inhibitor of Grp94, the ER-resident Hsp90. The effect manifested by compound 2 on several Grp94 and Hsp90α/β (cytosolic isoforms) clients were investigated. Compound 2 prevented intracellular trafficking of the Toll receptor, inhibited the secretion of IGF-II, affected the conformation of Grp94, and suppressed Drosophila larval growth, all Grp94-dependent processes. In contrast, compound 2 had no effect on cell viability or cytosolic Hsp90α/β client proteins at similar concentrations. The design, synthesis, and evaluation of 2 are described herein.     

Almost sure explosion of solutions to stochastic differential equations

This paper is concerned with the problem of explosive solutions for a class of stochastic differential equations. Our main results are presented as two theorems. Theorem 1 is concerned with the existence of explosive solutions with positive probability under certain sufficient conditions. With some additional mild conditions, it is shown in Theorem 2 that the explosion will occur almost surely. The methods of auxiliary functions and cycles are used in the proofs. Several remarks about their applications are given.