The effect of silver nanoparticles on the photocycle of bacteriorhodopsin of purple membranes of <Emphasis Type="Italic">Halobacterium salinarum</Emphasis>

The effect of silver nanoparticles (AgNPs) that are adsorbed on the surface of the purple membranes of Halobacterium salinarium bacteria on the optical properties and functional peculiarities of the lightsensitive protein bacteriorhodopsin (BR) has been demonstrated for the first time. Two mechanisms of the effect of AgNPs on the protein photocycle have been demonstrated using Raman scattering, giant Raman scattering, flash photolysis, and atomic force microscopy. It has been shown that the nanoparticles in the immediate spatial vicinity of BR fix its photocycle at the stage where it was at the moment of interaction with the nanoparticles. At greater distances, which reach three radii of an AgNPs, they have a weaker effect on BR, under which it retains the ability to be involved in the photocycle, however, has its parameters significantly changed. Thus, in the case of wild-type BR the photocycle accelerates and for the BR-D96N mutant it becomes slower. The data that are obtained could be of significance for creation of such optoelectronic hybrid systems with BR, where the parameters of its photocycle can be controlled using NPs. The results of the study may also be used in the field of nanobioengineering research, which is directed to creation of unique materials with controlled properties for recording and storage of information, energy transformation, and identification and characterization of trace amounts of analytes.     

Circular dichroism of the alkaloids ofPetilium raddeanum

The circular dichroism (CD) method has been used for studying the stereochemistry of steroid alkaloids containing an azomethine ring — petiline and petisine. In the CD spectrum of petiline a Cotton effect (CE) is observed in the 235 nm region which is due to a n * transition in the azomethine chromophore. The negative sign of this CE shows the 25S configuration in petiline. An analysis of CD spectra has shown that the 25S configuration is retained when petiline is oxidized to petisine.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 345–347, May–June, 1986.     

Chemisorption of biomolecules on a metal surface and its role in anomalously intensive Raman scattering

Amino acids and their derivatives are used as an example to study the mechanism of enhancement of the Raman spectra of molecules adsorbed on silver hydrosols. It is shown that adsorption occurs as a result of unshared electron pairs of nitrogen and oxygen atoms in amino and carboxyl groups, as well as a result of the formation of-electron bonds between aromatic rings and adsorption centers on the surface of the metal. It is shown that only the groups of atoms in direct contact with the metal undergo enhancement, i.e., the enhancement mechanism is local in character. A model of the bonding of amino acids with the metal surface is presented.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 33–37, March, 1985.     

Pellet freezing of in vitro produced bovine embryos using dry ice

In vitro produced bovine embryos were frozen by pellet freezing or vitrification method. In the pellet freezing method, the embryos were cooled on the dry ice and then frozen as pellets. At warming, the pellets were immersed directly into 0.5 M sucrose. The survival rates of blastocysts frozen by the pellet freezing method were higher (P<0.01) in 40% ethylene glycol (EG) than those in the lower concentrations (20 and 30% EG). Higher survival rates of blastocysts frozen by the pellet freezing method were obtained but the development rates did not differ, as compared with those by the vitrification method. There were no significant differences between the pellet freezing and vitrification method in the frequencies of post-thaw survival of hatched blastocysts. These results demonstrate that the pellet freezing method using dry ice can be used successfully for the cryopreservation of blastocysts.     

Analysis of laser-structure anisotropic semiconductors by the Bloch-function method

The method of Bloch functions is used to obtain the radiation makeup of a semiconductor laser structure consisting of periodically alternating waveguide and antiguide regions, and the differntial gains for the different modes are determined. Pumping of antiguide regions with different structure parameters makes it possible to obtain the maximum gains of a Bloch mode made up of outflowing waveguide modes at the center of the brillouin lobe. The directivity pattern contains in this case sideband satellites in addition to the central lobe. When the structure is optimized, the intensity of the central lobe amounts to 70% of the total emission intensity.Optoelectronics Laboratory, Lebedev Physics Institute, Academy of Sciences of the USSR. Translated from Preprint. No. 105 of the Lebedev Physics Institute, Academy of Sciences of the USSR, 1989.     

On the boundary value problem for the Sturm–Liouville equation with the discontinuous coefficient

We consider a boundary value problem for the Sturm–Liouville equation with piecewise‐constant leading coefficient. We prove that some integral representations for the solutions of the considered equation can be obtained by using classical transformation operators for the Sturm–Liouville operator at the end points of a finite interval. We also investigate the spectral characteristics of the boundary value problem, prove the completeness and expansion theorem. Copyright © 2012 John Wiley & Sons, Ltd.     

Derivatives of the alkaloid convolvine and their pharmacological activity

A series of new convolvine derivatives based on the alkaloid from Convolvulus subhirsutus and C. pseudocanthabrica were synthesized using alkylhalides and aliphatic and aromatic acid chlorides. Results of biological tests showed that convolvine and its derivatives exhibited pronounced antihypoxic, immunomodulating, and anti-inflammatory activity.     

Characterization of the scattering data for the Sturm–Liouville operator

This work studies the scattering problem on the real axis for the Sturm–Liouville equation with discontinuous leading coefficient and the real‐valued steplike potential q(x) that has different constant asymptotes as x → ± ∞ . We investigate the properties of the scattering data, obtain the main integral equations of the inverse scattering problem, and also give necessary and sufficient conditions characterizing the scattering data. Copyright © 2013 John Wiley & Sons, Ltd.