Effect of proton donors on the intramolecular coordination C=O→Si–F in (acyloxymethyl)trifluorosilanes. Ab initio,DFT and FTIR study,QTAIM analysis

The intramolecular С=O→Si coordination in H‐complexes of (acetoxymethyl)trifluorosilane and (benzoyloxymethyl)trifluorosilane with proton donors HCl, PhOH, MeOH, and CHCl₃ was investigated by density functional theory and second‐order Møller‐Plesset perturbation theory (MP2) methods. Interrelation and mutual influence of the intramolecular coordination bond С=O→Si and intermolecular hydrogen bonds C=O···H and Si–F···H in H‐complexes was established using the AIM and NBO analyses. The С=O→Si coordination is weakened by the C=O···H hydrogen bonding but enhanced by the Si–F_ax···H hydrogen bonding. The structure of H‐complexes of (acetoxymethyl)trifluorosilane with proton donors in solution was determined by comparing the ν(C=O) and ν(Si–F) frequencies calculated using the conductor‐like polarizable continuum model and their experimental Fourier transform infrared values. Copyright © 2014 John Wiley & Sons, Ltd.     

Metal-metabolomics of microalga Chlorella sorokiniana growing in selenium- and iodine-enriched media

The microalga Chlorella sorokiniana has been used to accumulate selenium and iodine from culture media enriched with these elements as a first stage in the production of supplemented foods. The microalgal colony was grown in a conventional culture medium containing iodine (KI) at concentrations in the range of 150?C4000 ??g mL^?1. Similar experiments were performed with selenium (SeO ₄ ^2? ) at concentrations in the range of 20?C500 ??g mL^?1. The concentration of iodine and selenium in the culture medium was analytically monitored daily and the viability of the colony was checked by biomass concentration measurement and by evaluation of the total content of chlorophyll and carotenoids. In addition, photosynthetic activity and the number of cells were also monitored. Iodine accumulation in the algal biomass increased rapidly with time and reached a steady state after 4 h of exposure. With Se exposure the colony viability decreased, although the culture grew well with concentrations of the element of 50 ??g mL^?1 in the culture medium; this experiment produced Se-enrichment in the alga (3 ??g g^?1) within 100 h. Sequential extraction of an algal pellet was performed in order to separate Se compounds according to their affinity with the following solvents: hot water to recover low molecular mass Se species, enzymatic extraction with driselase for species associated with the cell wall, sodium dodecyl sulphate (SDS) for water insoluble selenoproteins and, finally, enzymolysis with lipase and pronase that release and fragment residual selenoproteinsproducing compounds with low molecular mass. Size-exclusion chromatography (SEC) coupled with an ICP-MS detector showed the preponderance of Se-containing molecules with low molecular mass, possibly seleno-amino acids. Only a peak of low intensity located at 10 min was observed in the SDS extract that could be associated with a protein with molecular mass of 67 kDa. Finally, analysis of the aqueous extract of alga by reverse-phase chromatography with inductively-coupled plasma mass-spectrometry (RPC-ICP-MS) detection revealed the presence of selenocysteine (SeCys₂), selenomethylselenocysteine (SeMetSeCys), selenomethionine (SeMet), and Se(VI), particularly the last two species.     

Urinary calculi — atypical source of information on mercury in human biomonitoring

Chemical analysis of various biological matrices is routinely used for assessment of human exposure to various toxic metals. In this work, 489 samples of urinary calculi originating from almost the whole of The Czech Republic, were collected and subjected to mineralogical and elemental analysis. This study was aimed at mercury, the content of which was determined using thermo-oxidation — cold vapor — atomic absorption spectrometry. The effects of mineralogical composition, sex, age and region were recorded in order to verify the applicability of urinary calculi for biomonitoring. Relationships with other minor and trace elements were also investigated. Association of mercury with whewellite mineral was observed as well as a remarkable relationship with selenium, confirming the role of selenium in mercury excretion. No statistically significant effect was observed on the mercury content in stones with regard to the sex or region. Median values in age groups follow a trend with the maximum median value 0.365 mg kg^?1 in the group of 41–50 year old donors, decreasing to 0.060 mg kg^?1 for the oldest group (81–92 years). Our results confirm that urinary calculi can be helpful in providing complementary information on human exposure to mercury and its excretion.

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A two-step synthesis of medicinally-important 1,8-naphthalimide peptidyls by solid phase organic synthesis

A new approach for a short synthesis of novel medicinally-important mono-, bis- and tris-1,8-naphthalimide peptidyl derivatives is described. The method generates efficiently 1,8-naphthalimides with variable spacer lengths and charged, polar or hydrophobic residues at desired positions, which can increase binding affinity, conformational stability, intracellular transport and/or biological activity. The synthetic routes reported in this work are both general and applicable, and significantly expand the scope of potential 1,8-naphthalimide anticancer candidates.     

Ionic Liquid–Liquid Extraction and Supported Liquid Membrane Analysis of Lipophilic Wood Extractives from Dissolving-Grade Pulp

In this study, the extraction of lipophilic wood extractives from dissolving pulp samples using ionic liquid–liquid extraction and a two phase hollow fibre supported liquid membrane was investigated. Ionic liquids are capable of dissolving a range of organic and polymeric compounds and are biodegradable, with a negligible vapour pressure. Pulp samples were dissolved in a suitable amount of molten 1-butyl-3-methylimidazolium chloride to give 5 % cellulose solution. Pure cellulose was regenerated by adding water and filtered off. The ionic liquid-aqueous filtrate was first extracted for lipophilic extractives using liquid–liquid extraction. Then, a two phase hollow fibre supported liquid membrane extraction of lipophilic extractives was performed to extract the derivatized compounds prior to analysis by gas chromatography mass spectrometry. The operational parameters of this sample preparation approach were optimised using sterols and fatty acid methyl esters. The variation of enrichment factors and extraction efficiency with respect to liquid membrane, extraction time, stirring speed and sample pH were observed and used to get the optimal parameters. The approach was used in the analysis of oxygen bleached dissolving pulp samples in which main compounds identified were fatty acids, sterols, fatty alcohols, steroid hydrocarbons and ketones. These compounds were similar to those obtained using molecular solvent extraction method, which indicated the absence of chemical reaction between extractives and ionic liquid used.

     

Utilization of phosphinoamide ligands in homobimetallic fe and mn complexes: the effect of disparate coordination environments on metal-metal interactions and magnetic and redox properties

A series of homobimetallic phosphinoamide-bridged diiron and dimanganese complexes in which the two metals maintain different coordination environments have been synthesized. Systematic variation of the steric and electronic properties of the phosphinoamide phosphorus and nitrogen substituents leads to structurally different complexes. Reaction of [(i)PrNKPPh(2)] (1) with MCl(2) (M = Mn, Fe) affords the phosphinoamide-bridged bimetallic complexes [Mn((i)PrNPPh(2))(3)Mn((i)PrNPPh(2))] (3) and [Fe((i)PrNPPh(2))(3)Fe((i)PrNPPh(2))] (4). Complexes 3 and 4 are iso-structural, with one metal center preferentially binding to the three amide ligands in a trigonal planar arrangement while the second metal center is ligated by three phosphine donors. A fourth phosphinoamide ligand caps the tetrahedral coordination sphere of the phosphine-ligated metal center. M?ssbauer spectroscopy of complex 4 suggests that the metals in these complexes are best described as Fe(II) centers. In contrast, treatment of MnCl(2) or FeI(2) with [MesNKP(i)Pr(2)] (2) leads to the formation of the halide-bridged species [(THF)Mn(μ-Cl)(MesNP(i)Pr(2))(2)Mn(MesNP(i)Pr(2))] (5) and [(THF)Fe(μ-I)(MesNP(i)Pr(2))(2)FeI (7), respectively. Utilization of FeCl(2) in place of FeI(2), however, leads exclusively to the C(3)-symmetric complex [Fe(MesNP(i)Pr(2))(3)FeCl] (6), structurally similar to 4 but with a halide bound to the phosphine-ligated Fe center. The M?ssbauer spectrum of 6 is also consistent with high spin Fe(II) centers. Thus, in the case of the [(i)PrNPPh(2)](-) and [MesNP(i)Pr(2)](-) ligands, zwitterionic complexes with the two metals in disparate coordination environments are preferentially formed. In the case of the more electron-rich ligand [(i)PrNP(i)Pr(2)](-), complexes with a 2:1 mixed donor ligand arrangement, in which one of the ligand arms has reversed orientation relative to the previous examples, are formed exclusively when [(i)PrNLiP(i)Pr(2)] (generated in situ) is treated with MCl(2) (M = Mn, Fe): (THF)(3)LiCl[Mn(N(i)PrP(i)Pr(2))(2)(P(i)Pr(2)N(i)Pr)MnCl] (8) and [Fe(N(i)PrP(i)Pr(2))(2)(P(i)Pr(2)N(i)Pr)FeCl] (9). Bimetallic complexes 3-9 have been structurally characterized using X-ray crystallography, revealing Fe-Fe interatomic distances indicative of metal-metal bonding in complexes 6 and 9 (and perhaps 4, to a lesser extent). All of the complexes appear to adopt high spin electron configurations, and magnetic measurements indicate significant antiferromagnetic interactions in Mn(2) complexes 5 and 8 and no discernible magnetic superexchange in Fe(2) complex 4. The redox behavior of complexes 3-9 has also been investigated using cyclic voltammetry, and theoretical investigations (DFT) were performed to gain insight into the metal-metal interactions in these unique asymmetric complexes.     

Anti-Proliferative and Pro-Apoptotic Effects of Digested Aglianico Grape Pomace Extract in Human Colorectal Cancer Cells

Grape pomace (GP)—the major by-product of winemaking processes—still contains bioactive molecules with known beneficial properties for human health, such as an antiradical scavenging activity or an antiproliferative activity of tumors. In vitro studies have demonstrated that GP polyphenols specifically influence colon cancer cell proliferation. In addition to previously published work, we tested the phenolic compounds of Aglianico GP following an in vitro simulated gastrointestinal digestion on colorectal cancer cell lines at different degrees of differentiation. Our experiments, using HT29 and SW480 cells, confirmed the anti-proliferative effect of GP gastrointestinal digested extract and provided intriguing insights on the way it influences the cancer cell features (i.e., viability, proliferation, and apoptosis). We observed that Aglianico GP extract showed a great ability to affect cell proliferation and apoptosis. Interestingly, both HT29 and SW480 cells produced a significant increase in Bax, and a significant increase in the Bax/Bcl-2 ratio and caspase-3. The gastrointestinal digested GP extract was previously characterized both for antioxidant activity and phenolic composition. As a result, the TPC and the antioxidant activity reached high values in the Aglianico GP digested extract, and the main compounds assessed by UHPLC-DAD were anthocyanins, phenolic acids, and flavonoids. This work shed light on the use of digested GP extract as a dietary ingredient, a very sustainable source of nutritional compounds with potential health benefits for colon cancer cell proliferation.     

Solubilization of Nile Red in Micelles and Protomicelles of Sodium Dodecyl Sulfate

A spectrophotometric study of the solubilization and aggregation of the Nile red dye (NR) in premicellar and micellar aqueous solutions of sodium dodecyl sulfate (SDS) was carried out. The experiments were conducted both with saturated solutions of NR under conditions of thermodynamic equilibrium of the solution with a dye precipitate, and at a constant concentration of NR in a homogeneous solution. In the first case, it was proved theoretically and verified experimentally that with an increase in the SDS concentration, the NR concentration always increases, and at the limit of low concentrations, the dependence is linear. In both cases, the concentration of NR dimers as a function passes through a maximum in the premicellar region. There are no dimers in the micellar region. The extinction coefficients of NR monomers in SDS solutions were determined both below and above the critical micelle concentration (CMC) of SDS. A solubilization curve with branches for the premicellar and micellar regions was constructed, the intersection of which was used to find the CMC value in the system under study. The state of deep supersaturation of the NR solution in the metastable state upon dilution of the micellar system with water was studied. It was found that, in addition to dimers, molecular aggregates of higher orders were also formed.     

On the use of (TMS)3CH as novel tin-free radical reducing agent

(TMS)₃CH is an efficient free radical reducing agent. Debromination, deiodation, dechlorination as well as decarboxylation of Barton and Kim esters can proceed smoothly using this tin-free reducing agent. Rate constants for hydrogen atom abstraction from TMS₃CH by primary radicals were also determined.