Far-infrared radiation effect on the structure and properties of proteins

This paper describes the effect of far-infrared radiation on the activity and secondary structure of albumin, alcohol dehydrogenase, peroxidase and trypsin. For the first time the data obtained allowed a conclusion that enzymatic activity changes under the influence of radiation having the wavelength of 90 m. No disruptures of polypeptide chains or oligomerization of proteins were obtained. It has been shown that albumin secondary structure calculated from circular dichroism spectra changes lineary according to dose of laser emission.Abbreviations FIR far-infarred radiation - CD circular dichroism - ADG alcohol dehydrohenase - PXD peroxidase - ANS 1-anilinenaphalene-8-sulfonic acid     

Electronic structure of the 3,3′-bis-[η5-π-1,2-dicarba-3-nickel(III)-closododecaborate](1-) anion, {NiIII[η5-π-(3)-1,2-B,C2H11]2}, in salts with different cations,in salts with different cations

The results of the spectral and magnetochemical studies of some salts of the “sandwich-like” paramagnetic anion {Ni^III[η⁵-π-(3)-1,2-B⁹C₂H₁₁]₂}^– (I) with the Cs⁺, (CH₃)₄N⁺, and (C₆H₅)₄P⁺ cations and the cation complex of Fe(II) and 1,10-phenanthroline, [Fe^IIPhen₃]²⁺, are reported. The solid-phase IR, Raman, and X-ray photoelectron spectroscopy methods and optical spectroscopy of solutions were used. The effective magnetic moments (μ_eff) of Ni(III) in anion (I) were measured by the Faraday technique and corrected for the diamagnetism of the aromatic cluster ligands 1,2-B₉C₂H ₁₁ ²⁻ (II). It is established that μ_eff is weakly dependent on the nature of the cation. The problems concerned with the nature of the metal-ligand bonds in metal-carborane systems like (I) are discussed. The hypothesis of the charge transfer from ligands (II) to the transition metal atoms is validated, the donor ability rows of the π-ligands are introduced, and the cluster structure of the systems under study is attested. Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 37, No. 6, pp. 1060–1071, November–December, 1996. Translated by I. Izvekova     

Functionalization of the macropolyhedral borate anion cluster [B22H22]: isolation and characterization of the OH and OEt derivatives

Preparation and characterization of the first derivatives of the fused macropolyhedral anion [B₂₂H₂₂]²⁻ are reported. The species [B₂₂H₂₁OH]²⁻ (1) and [B₂₂H₂₁OEt]²⁻ (2) are obtained from workup of the products of the reaction between HgBr₂ and [NBzlEt₃]₂[B₂₂H₂₂]; a cluster involving the conjoining of a closo-B₁₂ icosahedron with a nido-B₁₀ cluster. Washing the products with ethanol followed by thin-layer chromatography allows the isolation of 1 and 2, reproducibly, in yields of 27 and 20%, respectively. The species were characterized by NMR spectroscopy, elemental analysis and X-ray diffraction studies. The crystal structure determinations of the two species identify novel features. Apparently the influence of the O atoms in the ions [B₂₂H₂₁OH]²⁻ and [B₂₂H₂₁OEt]²⁻ results in the lengthening of what was a gunwale B---B connection adjacent to the junction of the two cages such that the distances are 2.180 and 2.230 Å, respectively. These latter are longer than the corresponding distance in the parent species [B₂₂H₂₂]²⁻, which is 2.09 Å; quite long for a normal B---B distance. Thus it is assumed that these B atoms, in 1 and 2, one of which bears the substituent, are not bonded to each other.     

Adsorption at liquid interfaces: The generalized Frumkin isotherm and interfacial structure

The thermodynamics of adsorption of amphiphilic surface-active compounds at the interface between two immiscible liquids is considered. At the interface, these molecules are supposed to replace a few of the adsorbed molecules of both solvents. Classical isotherms of adsorption (Frumkin, Frumkin-Damaskin, Langmuir, Henry) were based on the model of non-penetrable interface, where an adsorbate can substitute only molecules of one solvent. At the interface between two immiscible electrolytes, nonpolar oil/water interfaces, and liquid membranes amphiphilic molecules can substitute molecules of both solvent and classic isotherms cannot be used. The generalization of Frumkin isotherm for permeable and non-permeable interfaces, known as the Markin-Volkov isotherm, gives the possibility to analyze adsorption in a general case. The adsorption isotherms of pentafluorobenzoic acid at the octane/water interface at different pHs were measured by the drop-weight method. The thermodynamic parameters of pentafluorobenzoic acid (PFBA) adsorption at octane/water interface were determined. From the measurements of PFBA adsorption, the structure of the octane/water interface was determined. Substitution of one adsorbed octane molecule requires approximately three adsorbed PFBA molecules. This result shows that the orientation of solvent molecules at the interface is different from the bulk. Adsorbed octane molecules have a lateral orientation with respect to the interface. Gibbs free energy of adsorption equilibrium and thermodynamic parameters of PFBA adsorption show that the adsorption of PFBA at the octane/water interface is accompanied by a reduction in the attraction between adsorbed PFBA molecules as the pH decreases to the acidic region. Published in Russian in Elektrokhimiya, 2006, Vol. 42, No. 10, pp. 1194–1200. The text was submitted by the authors in English.     

Resonance absorption of terahertz radiation in nanoperforated graphene

Recent measurements of the conductivity of nanoperforated graphene are interpreted in terms of edges states existing near the edge of each nanohole. The perimetric quantization of edge states should result in the formation of a quasi-equidistant ladder of quasistationary energy levels. Dirac fermions filling this ladder rotate about each nanohole in the direction determined by the valley index. It is shown that the irradiation of this system by circularly polarized terahertz radiation leads to a resonance in absorption in one of the valleys. The magnitude of absorption at the resonance frequency can be controlled by means of gate voltage.     

Two-Laser Thermal Lens Spectrometry with Signal Back-Synchronization

A two-laser dual-beam thermal lens spectrometer based on continuous-wave lasers, which implements the mode with signal back-synchronization, is developed with the aim to develop instrumentation for thermal lens spectrometry. This mode offers a potentially higher sensitivity of measurements in comparison with the lock-in mode of thermal lens measurements and variation of conditions depending on the measurement medium (solvent, or dispersed system, or solids). The wider possibilities of the back-synchronization mode in thermal lens spectrometry both for solving problems of chemical analysis and in some related fields are shown.     

Catalyst-Free Arylation of Tertiary Phosphines with Diaryliodonium Salts Enabled by Visible Light

The visible-light-induced arylation of tertiary phosphines with aryl(mesityl)iodonium triflates to produce the quaternary phosphonium salts occurs under mild, metal, and catalyst-free conditions. Photo-excited EDA complexes between diaryliodonium salts and phosphines supposedly enable this transformation, which is difficult to achieve through the traditional ground-state reactions. Demonstrating high functional group tolerance, broad scope, and complete selectivity of the aryl group transfer, the method is particularly compatible with sterically congested phosphines, which are challenging under metal-based catalytic methods.