Complex formation of β-brominated tetraphenylporphyrins and metal exchange of their cadmium complexes with <Emphasis Type="Italic">d</Emphasis>-metal salts in dimethylformamide

Complex formation of zinc and copper(II) acetates with tetraphenylporphyrin, 2-bromo-5,10,15,20-tetraphenylporphyrin, 2,3,12,13-tetrabromo-5,10,15,20-tetraphenylporphyrin, and 2,3,7,8,12,13,17,18-octabromo-5,10,15,20-tetraphenylporphyrin in N,N-dimethylformamide has been studied. The rate constants determined in the study of the complex formation and the metal exchange reactions have been compared.     

Synthesis of Intrinsically Disordered Fluorinated Peptides for Modular Design of High-Signal 19F MRI Agents

¹⁹F MRI is valuable for in vivo imaging due to the only trace amounts of fluorine in biological systems. Because of the low sensitivity of MRI however, designing new fluorochemicals remains a significant challenge for achieving sufficient ¹⁹F signal. Here, we describe a new class of high-signal, water-soluble fluorochemicals as ¹⁹F MRI imaging agents. A polyamide backbone is used for tuning the proteolytic stability to avoid retention within the body, which is a limitation of current state-of-the-art perfluorochemicals. We show that unstructured peptides containing alternating N-ϵ-trifluoroacetyllysine and lysine provide a degenerate ¹⁹F NMR signal. ¹⁹F MRI phantom images provide sufficient contrast at micromolar concentrations, showing promise for eventual clinical applications. Finally, the degenerate high signal characteristics were retained when conjugated to a large protein, indicating potential for in vivo targeting applications, including molecular imaging and cell tracking.     

Observed and Calculated Ionograms of Oblique Ionospheric Sounding on HF Radio Paths During a Magnetic Storm of September 7–8, 2017

Radiophysics and Quantum Electronics - Ionograms of the oblique ionospheric sounding radio paths Cyprus—Lovozero and Lovozero—Gor’kovskaya (near St. Petersburg) are analyzed using...     

Transport and toxicity of 5-fluorouracil,doxorubicin, and cyclophosphamide in in vitro placental barrier model based on BeWo b30 cells

An in vitro placental barrier model based on human choriocarcinoma BeWo b30 cell line was considered as a method of preclinical study of the transport and toxicity of antitumor agents and other organic compounds. Low permeabilities were found for 5-fluorouracil as an example of hydrophilic compound and for doxorubicin as an example of a lipophilic compound with a high degree of binding to proteins and DNA and a high permeability was found for cyclophosphamide as an example of lipophilic compound with a low degree of binding to proteins. Using impedance spectrometry and cell viability assessment via reduction of resazurin to resorufin, a pronounced cytotoxic effect of doxorubicin and good tolerance of 5-fluorouracil and cyclophosphamide by the cells were shown for drug concentrations equal to the maximum concentrations in the patients’ blood during the treatment of breast cancer.

     

Support vector machines for the estimation of aqueous solubility

Support Vector Machines (SVMs) are used to estimate aqueous solubility of organic compounds. A SVM equipped with a Tanimoto similarity kernel estimates solubility with accuracy comparable to results from other reported methods where the same data sets have been studied. Complete cross-validation on a diverse data set resulted in a root-mean-squared error = 0.62 and R(2) = 0.88. The data input to the machine is in the form of molecular fingerprints. No physical parameters are explicitly involved in calculations.     

Polyelectrolyte/magnetite nanoparticle multilayers: preparation and structure characterization

Polyelectrolyte composite planar films containing a different number of iron oxide (Fe3O4) nanoparticle layers have been prepared using the layer-by-layer adsorption technique. The nanocomposite assemblies were characterized by ellipsometry, UV-vis spectroscopy, and AFM. Linear growth of the multilayer thickness with the increase of the layer number, N, up to 12 reflects an extensive character of this parameter in this range. A more complicated behavior of the refractive index is caused by changes in the multilayer structure, especially for the thicker nanocomposites. A quantitative analysis of the nanocomposite structure is provided comparing a classical and a modified effective medium approach taking into account the influence of light absorption by the Fe3O4 nanoparticles on the complex refractive index of the nanocomposite and contributions of all components to film thickness. Dominant influence of co-adsorbed water on their properties was found to be another interesting peculiarity of the nanocomposite film. This effect, as well as possible film property modulation by light, is discussed.     

Quantitative studies on the respiratory burst generated in peritoneal macrophages

The luminol-dependent chemiluminescence of macrophages during the zymosan-stimulated respiratory burst has been studied both in the absence and in the presence of the radical inhibitor 3,5 di-tert-butyl-4-hydroxyphenyl propionic acid. In addition, the consumption of luminol and of the inhibitor has been followed analytically. Based on the rates of the consumption of the inhibitor, an iteration procedure yields a value of 2.2 × 10⁻⁷ M for the steady-state concentration of radicals generated by cells at the maximum of the chemiluminescence in the presence of inhibitor. Approximate calculations have indicated that under the experimental conditions applied, additional formation of superoxide anion radicals by the oxidation of luminol is negligible. By assuming that in an inhibitor-free system the disappearance of radicals takes place via their combination process as well as by their interaction with luminol and/or with luminol-derived species, numerical integration yields a calculated curve of radical concentration versus time in fair agreement with experimental data and a rate-constant value for the combination of radicals of 10⁶ M⁻¹ s⁻¹, supporting literature findings according to which primarily superoxide anion radicals are formed.