On primitive elements of algebraic function fields and models of $$X_0(N)$$ X 0 ( N )

The Ramanujan Journal - This paper is a continuation of our previous works where we study maps from $$X_0(N)$$ , $$N\ge 1$$ , into $${\mathbb {P}}^2$$ constructed via modular forms of the same...     

ICP-OES determination of metals present in textile materials

The aim of this work was to quantify the content of elements present in textile materials since it is known that textiles containing metals may represent a health hazard to consumers. Determination of metal content can be also useful to the textile industry since some metals present in textiles may contribute to problems during textile production. Extraction of metals from different textile materials was performed in an artificial acidic sweat solution according to the Öko Tex standard for materials coming into direct contact with the skin. After extraction from textile products made of cotton, flax, wool, silk, viscose, and polyester materials, all elements were determined by means of inductively coupled plasma-optical emission spectrometry (ICP-OES). Results in the sweat extracts (minimum-maximum in μg/mL) were: Al 0.11-1.58, Cd 0.02-0.05, Cr 0.01-0.32, Cu 0.05-1.95, Mn 0.01-2.17, and Ni 0.05-0.10. Concentrations of other elements were bellow detection limits. The total amount of metals present was determined after microwave assisted acidic digestion of textile materials with 7 M nitric acid. According to the results, the majority of the detected elements were below the concentration limits given by the Öko Tex, and for this reason the textile materials investigated do not represent a health hazard to consumers.     

Synthesis of poly(oxyethylene phosphoramidate)s and glycopolymers via Staudinger reaction: Multivalent binding studies with Concanavalin A

A new method for the preparation of poly(oxyethylene phosphoramidate)s and glycopolymers is developed via modification of poly(oxyethylene H‐phosphonate) which is a biodegradable, biocompatible and low toxic polymer. The phosphonate groups of the precursor are converted into tri‐coordinated phosphorus species yielding poly(oxyethylene trimethylsilyl phosphite). The latter is then reacted with different azides, including sugar azides, via Staudinger reaction to furnish the desired poly(oxyethylene phosphoramidate)s and such containing sugar moieties in the side chains attached to the P‐centers. 2002P NMR spectroscopy is applied as a powerful tool for determination of the conversion and structure of the reaction products. Studies on Concanavalin A binding to the obtained glycopolymers are performed using dynamic light scattering and analytical ultracentrifugation techniques. The viability of Human Embryonic Kidney 293 cell line is slightly affected when exposed to polyphosphoramidate glucoconjugate over a broad range of concentrations. The results obtained are encouraging for further investigations on the clustering and bio‐recognition properties of the synthesized glycopolymers. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 1730–1741     

Reaction kinetics of resveratrol with tert-butoxyl radicals

The rate constant for the reaction of t-butoxyl radicals with resveratrol was studied under pseudo-first order conditions. The rate constant was determined by measuring the phenoxyl radical formation rate at 390 nm as function of resveratrol concentration in acetonitrile. The rate constant was determined to be 6.5×10⁸ M^?1s^?1. This high value indicates the high reactivity consistent with the strong antioxidant activity of resveratrol.     

Stibinidene and Bismuthinidene as Two‐Electron Donors for Transition Metals (Co and Mn)

The reaction of stibinidene and bismuthinidene ArM [where Ar=C₆H₃‐2,6‐(CH=NtBu)₂; M=Sb ( 1 ), Bi ( 2 )] with transition metal (TM) carbonyls Co₂(CO)₈ and Mn₂(CO)₁₀ produced unprecedented ionic complexes [(ArM)₂Co(CO)₃]⁺[Co(CO)₄]^? and [(ArM)₂Mn(CO)₄]⁺[Mn(CO)₅]^? [where M=Sb ( 3 , 5 ), Bi ( 4 , 6 )]. The pnictinidenes 1 and 2 behaved as two‐electron donors in this set of compounds. Besides the M→TM bonds, the topological analysis also revealed a number of secondary interactions contributing to the stabilization of cationic parts of titled complexes.     

Guanine Substitutions Prevent Conformational Switch from Antiparallel to Parallel G-Quadruplex

Guanine quadruplexes, recently reported to form in vivo, represent a broad spectrum of non-canonical conformations of nucleic acids. The actual conformation might differ between water solutions and crowding or dehydrating solutions that better reflect the conditions in the cell. Here we show, using spectroscopic techniques, that most guanine substitutions prevent the conformational switch from antiparallel or hybrid forms to parallel ones when induced by dehydrating agents. The inhibitory effect does not depend on the position of the substitution, but, interestingly, on the type of substitution and, to some extent, on its destabilising potential. A parallel form might be induced in some cases by ligands such as N-methyl mesoporphyrin IX and even this ligand-induced switch is inhibited by guanine substitution. The ability or inability to have a conformation switch, based on actual conditions, might significantly influence potential conformation-dependent quadruplex interactions.     

Geometrostatic Manifolds of Small ADM Mass

We bound the locations of outermost minimal surfaces in geometrostatic manifolds whose ADM mass is small relative to the separation between the black holes and prove the intrinsic flat stability of the positive mass theorem in this setting. © 2018 Wiley Periodicals, Inc.     

Analysis of enantiomers in biological matrices by charged cyclodextrin-mediated capillary zone electrophoresis in column-coupling arrangement with capillary isotachophoresis

The possibility to apply charged chiral selector as buffer additive in capillary zone electrophoresis (CZE) on-line coupled with capillary isotachophoresis (CITP) was studied. Enantioseparations and determinations of trace (ng/ml) antihistaminic drugs [pheniramine (PHM), dimethindene (DIM), dioxopromethazine (DIO)] present in samples of complex ionic matrices (urine) served as model examples. A negatively charged carboxyethyl-β-cyclodextrin (CE-β-CD) was used as a chiral selector in analytical CZE stage following upon a sample pretreatment by CITP (preconcentration of the analytes from 5 to 20-times diluted urine samples, partial sample clean up removing macroconstituents from the sample matrices). A high recognition capability of the oppositely charged CE-β-CD was demonstrated by enantioselective retardation of the drugs in presence of micro-and semi-macroconstituents migrating in CZE stage and detectable by UV detector. In this way, enantiomers of the drugs could be easily separated and determined. Due to lack of interferences between the drugs and sample-matrix constituents in presence of charged CE-β-CD, demands on both spacers in CITP step and multiple column-switching were minimized. CITP-CZE method with charged selector appeared to be a useful analytical approach for the trace enantiomers in complex ionic matrices as it combined enhanced separation selectivity and sample loadabitlity with high separation efficiency and provided favorable performance parameters including sensitivity, linearity, precision, accuracy/recovery and robustness with minimal demands on sample preparation. Analysis of urine sample taken from a patient treated by PHM, showing concentration profile of PHM enantiomers and their metabolites, illustrated potentialities of the method in clinical research.     

Fluorescence properties of selected benzo[c]phenantridine alkaloids and studies of their interaction with CT DNA

The spectral, especially fluorescence properties, of seven selected quaternary benzo[c]phenantridine alkaloids (sanguinarine, chelerythrine, chelirubine, sanguirubine, chelilutine, sanguilutine, and macarpine) were studied in presence and in absence of double-stranded DNA. This study has proved dramatic differences in fluorescence emission of all studied alkaloids in presence of calf thymus DNA in comparison to fluorescence of free alkaloids. The most remarkable are changes in emission spectra of macarpine, chelirubine, and sanguirubine. Association constants (logK) for interaction of all studied alkaloids with CT DNA were calculated.     

Stereoselectivity of 1,3-dipolar cycloadditions of l-valine-derived nitrones with methyl acrylate

Chiral nitrones derived from l-valine react with methyl acrylate to afford the corresponding diastereomeric 3,5-disubstituted isoxazolidines. The dibenzylsubstituted nitrone gave also 3,4-disubstituted isoxazolidine in 4% yield, additionally. The stereoselectivity was dependent on the steric hindrance of the nitrone and reaction conditions. High pressure decreased the reaction time of the cycloadditions. The major products were found to have the C-3/C-6 erythro and C-3/C-5 trans relative configuration. The major cycloadduct undergoes N-O cleavage and deprotection to a chiral diaminodiol derivative.