Electrochemical Behavior of Sulfur in Aqueous Alkaline Solutions

Russian Journal of Physical Chemistry A - The kinetics and mechanism of the electrode oxidation-reduction of sulfur on an electrically conductive sulfur–graphite electrode in an alkaline...     

Sulfobetaine derivatives of thiacalix[4]arene: synthesis and supramolecular self-assembly of submicron aggregates with AgI cations

1. Download high-res image (116KB)
2. Download full-size image

     

A study of the hydration of ribonuclease A using isothermal calorimetry

This work is part of a systematic study undertaken to find the excess thermodynamic functions of binary protein–water systems. Isothermal calorimetry and water sorption measurements were applied to characterize the hydration dependencies of the excess thermodynamic functions. The advantages of our methodology are (i) we are able to simultaneously determine the excess partial quantities of water and proteins; (ii) these thermodynamic quantities can be determined in the entire range of water content. Here, in particular, the excess partial enthalpies of water and bovine pancreatic ribonuclease A (RNase A) have been determined. The excess partial enthalpies for RNase A are compared with the published data for several unrelated globular proteins (lysozyme, chymotrypsinogen A, serum albumin, lactoglobulin). These biomacromolecules represent a series of proteins in which the hydrophobicity of proteins is gradually changed in a wide range. It was found that the excess partial quantities for the studied proteins are determined by the hydration of the hydrophilic and hydrophobic protein groups. The more hydrophilic a protein, the more significant a hydrophilic hydration contribution is and vice versa. RNase A is the most hydrophilic protein under the study. This protein has the most significant hydrophilic hydration contribution. Lactoglobulin is the most hydrophobic protein under the study. This protein has the most significant hydrophobic hydration contribution.     

Electrical conductivity of solutions of copper(II) nitrate crystalohydrate in dimethyl sulfoxide

Conductometry is used to investigate the electric conductivity of Cu(NO₃)₂ ? 3Н₂О solutions in dimethyl sulfoxide in the 0.01–2.82 M range of concentrations and at temperatures of 288–318 K. The limiting molar conductivity of the electrolyte and the mobility of Cu²⁺ and NO₃^- ions, the effective coefficients of diffusion of copper(II) ions and nitrate ions, and the degree and constant of electrolytic dissociation are calculated for different temperatures from the experimental results. It is established that solutions containing 0.1–0.6 M copper nitrate trihydrate in DMSO having low viscosity and high electrical conductivity can be used in electrochemical deposition.     

Anticancer Cytotoxic Activity of Bispidine Derivatives Associated with the Increasing Catabolism of Polyamines

Polyamine (PA) catabolism is often reduced in cancer cells. The activation of this metabolic pathway produces cytotoxic substances that might cause apoptosis in cancer cells. Chemical compounds able to restore the level of PA catabolism in tumors could become potential antineoplastic agents. The search for activators of PA catabolism among bicyclononan-9-ones is a promising strategy for drug development. The aim of the study was to evaluate the biological activity of new 3,7-diazabicyclo[3.3.1]nonan-9-one derivatives that have antiproliferative properties by accelerating PA catabolism. Eight bispidine derivatives were synthetized and demonstrated the ability to activate PA catabolism in regenerating rat liver homogenates. However, only three of them demonstrated a potent ability to decrease the viability of cancer cells in the MTT assay. Compounds 4c and 4e could induce apoptosis more effectively in cancer HepG2 cells rather than in normal WI-38 fibroblasts. The lead compound 4e could significantly enhance cancer cell death, but not the death of normal cells if PAs were added to the cell culture media. Thus, the bispidine derivative 4e 3-(3-methoxypropyl)-7-[3-(1H-piperazin-1-yl)ethyl]-3,7-diazabicyclo[3.3.1]nonane could become a potential anticancer drug substance whose mechanism relies on the induction of PA catabolism in cancer cells.     

Retardation effects from quark confinement on low-energy nucleon dynamics

We investigate effects from quark confinement on low-energy nucleon dynamics. These effects are shown to give rise to a peculiar dynamical situation: Low-energy nucleon dynamics is not Hamiltonian and is governed by a nonlocal-in-time interaction operator. In the leading order of the two-nucleon EFT we show that after renormalization the nucleon dynamics is governed by the same interaction operator.     

Structure–Activity Relationship of the Thiacalix[4]arenes Family with Sulfobetaine Fragments: Self-Assembly and Cytotoxic Effect against Cancer Cell Lines

Regulating the structure of macrocyclic host molecules and supramolecular assemblies is crucial because the structure–activity relationship often plays a role in governing the properties of these systems. Herein, we propose and develop an approach to the synthesis of the family of sulfobetaine functionalized thiacalix[4]arenes with regulation of the self-assembly and cytotoxic effect against cancer cell lines. The dynamic light scattering method showed that the synthesized macrocycles in cone, partial cone and 1,3-alternate conformations form submicron-sized particles with Ag⁺ in water, but the particle size and polydispersity of the systems studied depend on the macrocycle conformation. Based on the results obtained by ¹H and ¹H-¹H NOESY NMR spectroscopy and transmission electron microscopy for the macrocycles and their aggregates with Ag⁺, a coordination scheme for the Ag⁺ and different conformations of p-tert-butylthiacalix[4]arene functionalized with sulfobetaine fragments was proposed. The type of coordination determines the different shapes of the associates. Cytotoxic properties are shown to be controlled by the shape of associates, with the highest activity demonstrated by thiacalix[4]arenes in partial cone conformation. This complex partial cone/Ag⁺ is two times higher than the reference drug imatinib mesylate. High selectivity against cervical carcinoma cell line indicates the prospect of their using as components of new anticancer system.     

Formation of 1,2,4-oxadiazoles in the course of photooxidation of aromatic azides in acetonitrile

1. Download : Download high-res image (127KB)
2. Download : Download full-size image

     

New Calix[4]arene—Fluoresceine Conjugate by Click Approach—Synthesis and Preparation of Photocatalytically Active Solid Lipid Nanoparticles

New fluorescent systems for photocatalysis, sensors, labeling, etc., are in great demand. Amphiphilic ones are of special interest since they can form functional colloidal systems that can be used in aqueous solutions. A new macrocycle platform for click chemistry and its adduct with o-propargylfluoresceine was synthesized and characterized using modern physical techniques. Nanosized solid lipid nanoparticles (SLNs) from the calixarene—fluoresceine adduct were synthesized through the solvent injection technique and well-characterized in the solution and in solid state using light-scattering and microscopy methods. The maximum fluorescence intensity of the SLNs was found to be in the pH range from 7 to 10. The Förster resonance energy transfer (FRET) efficiency from SLNs to rhodamine 6g was found to be 97.8%. Finally, pure SLNs and the FRET system SLNs—Rh6G were tested in model photocatalytic ipso oxidative hydroxylation of phenylboronic acid under blue LED light. The SLNs—Rh6G system was found to be the best, giving an almost qualitative phenol yield, which was shown by HPLC-UV analysis.     

The Design,Synthesis, and Biological Activities of Pyrrole-Based Carboxamides: The Novel Tubulin Inhibitors Targeting the Colchicine-Binding Site

Microtubule targeting agents (MTAs) that interfere with the dynamic state of the mitotic spindle are well-known and effective chemotherapeutic agents. These agents interrupt the microtubule network via polymerization or depolymerization, halting the cell cycle progression and leading to apoptosis. We report two novel pyrrole-based carboxamides (CAs) (CA-61 and -84) as the compounds exhibiting potent anti-cancer properties against a broad spectrum of epithelial cancer cell lines, including breast, lung, and prostate cancer. The anti-cancer activity of CAs is due to their ability to interfere with the microtubules network and inhibit tubulin polymerization. Molecular docking demonstrated an efficient binding between these ligands and the colchicine-binding site on the tubulin. CA-61 formed two hydrogen bond interactions with THR 179 (B) and THR 353 (B), whereas two hydrogen bonds with LYS 254 (B) and 1 with ASN 101 (A) were identified for CA-84. The binding energy for CA-84 and CA-61 was −9.910 kcal/mol and −9.390 kcal/mol. A tubulin polymerization assay revealed a strong inhibition of tubulin polymerization induced by CA-61 and -84. The immunofluorescence data revealed the disruption of the tubulin assembly in CA-treated cancer cells. As an outcome of the tubulin inhibition, these compounds halted the cell cycle progression in the G2/M phase, leading to the accumulation of the mitotic cells, and further induced apoptosis. Lastly, the in vivo study indicated that CAs significantly inhibited the HCC1806 breast cancer xenograft tumor growth in a nude mouse model. Collectively, we identified the novel CAs as potent MTAs, inhibiting tubulin polymerization via binding to the colchicine-binding site, disrupting the microtubule network, and exhibiting potent pro-apoptotic activities against the epithelial cancer cell lines both in vitro and in vivo.