Steroid template associated peptides: design, synthesis and 2D NMR characterization of a novel protected 18-Phe,19-Gly-containing steroidal compound

We report herein the synthesis of a novel modified steroid with two rigidly positioned amino acids in C- and N-protected forms (Gly-O^tBu and N-Fmoc-l-Phe) at the angular positions (C-18 methylamino group and C-19 carboxylic function) of the steroid nucleus via amide bonds, starting from 18-cyanopregnenolone acetate over 10 steps. In an attempt to gain more insight into the structural and conformational features of this novel 18-Phe,19-Gly-containing steroidal compound, we describe the detailed 2D NMR spectral analysis. Despite the large size and the conformational flexibility of the amino acid units in this molecule, conformational analysis by NOESY connectivities showed the existence of mainly one conformation (∼95%) in CDCl₃ solution with approximately parallel orientation of the phenylalanine and glycine moieties.     

The Effect of pH on OH Radical Generation in Aqueous Solutions by Atmospheric Pressure Glow Discharge

Formation of hydroxyl radicals in aqueous solutions by atmospheric pressure DC glow discharge was investigated. The ferrocyanide was used as an OH scavenger at different pH. Experimental results indicated that pH effect on hydroxyl radical formation rate could be explained by particularities of [Fe(CN)₆]^4? and reactive species interaction in different media.     

Two crown‐ether‐coordinated caesium halogen salts

The crystal structures of two crown‐ether‐coordinated caesium halogen salt hydrates, namely di‐μ‐bromido‐bis[aqua(1,4,7,10,13,16‐hexaoxacyclooctadecane)caesium(I)] dihydrate, [Cs₂Br₂(C₁₂H₂₄O₆)₂(H₂O)₂]·2H₂O, (I), and poly[[diaquadi‐μ‐chlorido‐μ‐(1,4,7,10,13,16‐hexaoxacyclooctadecane)dicaesium(I)] dihydrate], {[Cs₂Cl₂(C₁₂H₂₄O₆)(H₂O)₂]·2H₂O}_n, (II), are reported. In (I), all atoms are located on general positions. In (II), the Cs⁺ cation is located on a mirror plane perpendicular to the a axis, the chloride anion is located on a mirror plane perpendicular to the c axis and the crown‐ether ring is located around a special position with site symmetry 2/m, with two opposite O atoms exactly on the mirror plane perpendicular to the a axis; of one water molecule, only the O atom is located on a mirror plane perpendicular on the a axis, while the other water molecule is completely located on a mirror plane perpendicular to the c axis. Whereas in (I), hydrogen bonds between bromide ligands and water molecules lead to one‐dimensional chains running along the b axis, in (II) two‐dimensional sheets of water molecules and chloride ligands are formed which combine with the polymeric caesium–crown polymer to give a three‐dimensional network. Although both compounds have a similar composition, i.e. a Cs⁺ cation with a halogen, an 18‐crown‐6 ether and a water ligand, the crystal structures are rather different. On the other hand, it is remarkable that (I) is isomorphous with the already published iodide compound.     

Glucose biosensor based on graphite electrodes modified with glucose oxidase and colloidal gold nanoparticles

The electrochemistry of glucose oxidase (GOx) immobilized on a graphite rod electrode modified by gold nanoparticles (Au-NPs) was studied. Two types of amperometric glucose sensors based on GOx immobilized and Au-NPs modified working electrode (Au-NPs/GOx/graphite and GOx/Au-NPs/graphite) were designed and tested in the presence and the absence of N-methylphenazonium methyl sulphate in different buffers. Results were compared to those obtained with similar electrodes not containing Au-NPs (GOx/graphite). This study shows that the application of Au-NPs increases the rate of mediated electron transfer. Major analytical characteristics of the amperometric biosensor based on GOx and 13 nm diameter Au-NPs were determined. The analytical signal was linearly related to glucose concentration in the range from 0.1 to 10 mmol L^?1. The detection limit for glucose was found within 0.1 mmol L^?1 and 0.08 mmol L^?1 and the relative standard deviation in the range of 0.1–100 mol L^?1 was 0.04–0.39%. The τ_1/2 of V _max characterizes the storage stability of sensors: this parameter for the developed GOx/graphite electrode was 49.3 days and for GOx/Au-NPs/graphite electrode was 19.5 days. The sensor might be suitable for determination of glucose in beverages and/or in food.     

Chemical Evaluation,Antioxidant, Antiproliferative,Anti-Inflammatory and Antibacterial Activities of Organic Extract and Semi-Purified Fractions of the Adriatic Sea Fan,Eunicella cavolini

Due to sedentary lifestyle and harsh environmental conditions, gorgonian coral extracts are recognized as a rich source of novel compounds with various biological activities, of interest to the pharmaceutical and cosmetic industries. The presented study aimed to perform chemical screening of organic extracts and semi-purified fractions obtained from the common Adriatic gorgonian, sea fan, Eunicella cavolini (Koch, 1887) and explore its abilities to exert different biological effects in vitro. Qualitative chemical evaluation revealed the presence of several classes of secondary metabolites extended with mass spectrometry analysis and tentative dereplication by using Global Natural Product Social Molecular Networking online platform (GNPS). Furthermore, fractions F4 and F3 showed the highest phenolic (3.28 ± 0.04 mg GAE/g sample) and carotene (23.11 ± 2.48 mg β-CA/g sample) content, respectively. The fraction F3 inhibited 50% of DPPH (2,2-diphenyl-1-picryl-hydrazyl-hydrate) and ABTS (2,2′-azino-bis (3-ethylbenzthiazolin-6-yl) sulfonic acid) radicals at the concentrations of 767.09 ± 11.57 and 157.16 ± 10.83 µg/mL, respectively. The highest anti-inflammatory potential was exhibited by F2 (IC₅₀ = 198.70 ± 28.77 µg/mL) regarding the inhibition of albumin denaturation and F1 (IC₅₀ = 254.49 ± 49.17 µg/mL) in terms of soybean lipoxygenase inhibition. In addition, the most pronounced antiproliferative effects were observed for all samples (IC₅₀ ranging from 0.82 ± 0.14–231.18 ± 46.13 µg/mL) against several carcinoma cell lines, but also towards non-transformed human fibroblasts pointing to a generally cytotoxic effect. In addition, the antibacterial activity was tested by broth microdilution assay against three human pathogenic bacteria: Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus. The latter was the most affected by fractions F2 and F3. Finally, further purification, isolation and characterization of pure compounds from the most active fractions are under investigation.     

X-ray fluorescence analysis of the systems Fe–Ni–Mo/Cr

A procedure has been developed for the X-ray fluorescence determination of the thickness of Fe-No-Mo/Cr two-layer films supported on polycor. Correction coefficients have been calculated that take into account the effects of the mutual influence of the elements in this system. The density of the materials in the films has been experimentally determined. The performance characteristics of the developed procedure are provided.     

Determination of Traces of Toxic Elements in Dimethylaminoborane upon Their Concentration for Atomic Emission Analysis

A technique of atomic emission determination of traces of toxic elements in dimethylaminoborane with detection limits of n·10^–5–10^–8 wt. % has been developed. To reduce the detection limits, a technique of separation of the basic component in the form of boron fluoride, with concentration of microimpurities on a graphite collector, was used.     

A laser-erosion collector for microspectral analysis of solid inorganic materials

To carry out a microspectral analysis of solid inorganic materials with preliminary laser sampling, we suggest a collector consisting of two thin graphite semidisks, which in sampling are installed on the specimen surface with a certain gap for passage of laser radiation. The specific features and analytical application of the collector are considered. Scientific-Research Institute of Chemistry at the Nizhni Novgorod State University, 23, bl. 5, Gagarin Ave., Nizhini Novgorod, 603600, Russia. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 6, pp. 839–842, November–December, 1998.