Role of hydrogen disulfide in the vulcanization process

Summary It was shown that the breakdown of hydrogen disulfide in a-olefins results in the exclusive formation of addition products (mono-, di-, and tetra-sulfides) without formation of hydrogen sulfide and free sulfur.Similar results were obtained when sulfur reacted with monoethanolamine (vulcanization accelerator) in -olefin solution.The reaction products were isolated and characterized.     

ACTH(6–9)PGP Peptide Protects SH-SY5Y Cells from H2O2, tert-Butyl Hydroperoxide,and Cyanide Cytotoxicity via Stimulation of Proliferation and Induction of Prosurvival-Related Genes

Stabilized melanocortin analog peptide ACTH(6–9)PGP (HFRWPGP) possesses a wide range of neuroprotective activities. However, its mechanism of action remains poorly understood. In this paper, we present a study of the proproliferative and cytoprotective activity of the adrenocorticotropic hormone fragment 6–9 (HFRW) linked with the peptide prolyine–glycyl–proline on the SH-SY5Y cells in the model of oxidative stress-related toxicity. The peptide dose-dependently protected cells from H₂O₂, tert-butyl hydroperoxide, and KCN and demonstrated proproliferative activity. The mechanism of its action was the modulation of proliferation-related NF-κB genes and stimulation of prosurvival NRF2-gene-related pathway, as well as a decrease in apoptosis.     

Novel Rearrangement of 3‐Acylaminofuro[2,3‐b]pyridines into 3‐(oxazol‐4‐yl)pyridin‐2‐ones

3‐Acylaminofuro[2,3‐b]pyridine derivatives have been synthesized, and their behavior under acidic and basic conditions was studied. A new base‐catalyzed rearrangement of 3‐acylaminofuro[2,3‐b]pyridine derivatives into 3‐(oxazol‐4‐yl)pyridine‐2‐ones has been founded.     

Evidence from Raman spectroscopy that InhA, the mycobacterial enoyl reductase, modulates the conformation of the NADH cofactor to promote catalysis

InhA, the enoyl reductase from Mycobacterium tuberculosis, catalyzes the NADH-dependent reduction of trans-2-enoyl-ACPs. In the present work, Raman spectroscopy has been used to identify catalytically relevant changes in the conformation of the nicotinamide ring that occur when NADH binds to InhA. For 4(S)-NADD, there is an 11 cm-1 decrease in the wavenumber of the C4-D stretching band (nuC-D) and a 50% decrease in the width of this band upon binding to InhA. While a similar reduction in line width is observed for the corresponding band arising from 4(R)-NADD, nuC-D for this isomer increases 34 cm-1 upon binding to InhA. These changes in nuC-D indicate that the nicotinamide ring adopts a bound conformation in which the 4(S)C-D bond is in a pseudoaxial orientation. Mutagenesis of F149, a conserved active site residue close to the cofactor, demonstrates that this enzyme-induced modulation in cofactor structure is directly linked to catalysis. In contrast to the wild-type enzyme, Raman spectra of NADD bound to F149A InhA resemble those of NADD in solution. Consequently, F149A is no longer able to optimally position the cofactor for hydride transfer, which correlates with the 30-fold decrease in kcat and 2-fold increase in D(V/KNADH) caused by this mutation. These studies thus substantiate the proposal that hydride transfer is promoted by pseudoaxial positioning of the NADH pro-4S bond, and indicate that catalysis of substrate reduction by InhA results, in part, from correct orientation of the cofactor in the ground state.     

4,5-Bis(arylethynyl)-1,2,3-triazoles—A New Class of Fluorescent Labels: Synthesis and Applications

Cu-catalyzed 1,3-dipolar cycloaddition of ethyl 2-azidoacetate to iodobuta-1,3-diynes and subsequent Sonogashira cross-coupling were used to synthesize a large series of new triazole-based push–pull chromophores: 4,5-bis(arylethynyl)-1H-1,2,3-triazoles. The study of their optical properties revealed that all molecules have fluorescence properties, the Stokes shift values of which exceed 150 nm. The fluorescent properties of triazoles are easily adjustable depending on the nature of the substituents attached to aryl rings of the arylethynyl moieties at the C4 and C5 atoms of the triazole core. The possibility of 4,5-bis(arylethynyl)-1,2,3-triazoles’ application for labeling was demonstrated using proteins and the HEK293 cell line. The results of an MTT test on two distinct cell lines, HEK293 and HeLa, revealed the low cytotoxicity of 4,5-bis(arylethynyl)triazoles, which makes them promising fluorescent tags for labeling and tracking biomolecules.     

Anti-Proliferative and Cytoprotective Activity of Aryl Carbamate and Aryl Urea Derivatives with Alkyl Groups and Chlorine as Substituents

Natural cytokinines are a promising group of cytoprotective and anti-tumor agents. In this research, we synthesized a set of aryl carbamate, pyridyl urea, and aryl urea cytokinine analogs with alkyl and chlorine substitutions and tested their antiproliferative activity in MDA-MB-231, A-375, and U-87 MG cell lines, and cytoprotective properties in H₂O₂ and CoCl₂ models. Aryl carbamates with the oxamate moiety were selectively anti-proliferative for the cancer cell lines tested, while the aryl ureas were inactive. In the cytoprotection studies, the same aryl carbamates were able to counteract the CoCl₂ cytotoxicity by 3–8%. The possible molecular targets of the aryl carbamates during the anti-proliferative action were the adenosine A2 receptor and CDK2. The obtained results are promising for the development of novel anti-cancer therapeutics.     

Supramolecular interaction of transition metal complexes with albumins and DNA: Spectroscopic methods of estimation of binding parameters

Binding parameters of metal complexes with albumins and DNA since the middle of 1990s are considered and summarized. The most widespread spectroscopic methods of estimation of binding parameters are discussed – direct fluorescent methods, indirect fluorescent methods (by fluorescence quenching parameters), and ways of estimation of binding constants by other optical spectroscopic methods. The methods and approaches to calculations used for the determination of binding constants are discussed. The data on the already found binding constants and kinetic parameters is systematized.     

Convergence Rate of Galerkin Method for a Certain Class of Nonlinear Operator-Differential Equations

In this article, we study a Galerkin method for a nonstationary operator equation with a leading self-adjoint operator A(t) and a subordinate nonlinear operator F. The existence of the strong solutions of the Cauchy problem for differential and approximate equations are proved. New error estimates for the approximate solutions and their derivatives are obtained. The developed method is applied to an initial boundary value problem for a partial differential equation of parabolic type.     

Noble metal nanostructure both as a SERS nanotag and an analyte probe

We report nanotags encapsulated in Au-Ag nanostructure that are active in surface-enhanced Raman scattering. The Au-Ag nanoshells are filled with Ag via citrate reduction, entrapping label molecules in the process. The nanotags can be used for quantitative SERS measurements with the label molecules as internal reference.