Crystal and molecular structure of cesium hydrogen malonate

The title compound is C₃H₃O₄Cs, CsHM, monoclinic,P2₁/c,a=8.393 (3),b=7.960(2),c=9.023(2) Å,=92.11(2)°. The structure was solved by the heavy-atom method and refined by least-squares techniques to anR factor of 0.023 for 760 observed reflections. The CsHM has no internal symmetry and one carboxy group, but not the other, is twisted almost at right angles (96°) to the plane of the three central carbon atoms. The hydrogen malonate anions are linked together by two short and symmetrical O-HO hydrogen bonds [2.468(4) and 2.482(4) Å]. The structure consists of hydrogen malonate chains cross-linked by the Cs⁺ ion. The IR spectrum of CsHM has been analyzed.     

Finite element LES and VMS methods on tetrahedral meshes

Finite element methods for problems given in complex domains are often based on tetrahedral meshes. This paper demonstrates that the so-called rational Large Eddy Simulation model and a projection-based Variational Multiscale method can be extended in a straightforward way to tetrahedral meshes. Numerical studies are performed with an inf-sup stable second order pair of finite elements with discontinuous pressure approximation.     

Cellular Target of a Rhodium Metalloinsertor is the DNA Base Pair Mismatch

Defects in DNA mismatch repair (MMR) are commonly found in various cancers, especially in colorectal cancers. Despite the high prevalence of MMR-deficient cancers, mismatch-targeted therapeutics are limited and diagnostic tools are indirect. Here, we examine the cytotoxic properties of a rhodium metalloinsertor, [Rh(phen)(chrysi)(PPO)]²⁺ ( RhPPO ) in 27 diverse colorectal cancer cell lines. Despite the low frequency of genomic mismatches and the non-covalent nature of the RhPPO -DNA lesion, RhPPO is on average five times more potent than cisplatin. Importantly, the biological target and profile for RhPPO differs from that of cisplatin. A fluorescent metalloinsertor, RhCy3 , was used to demonstrate that the cellular target of RhPPO is the DNA mismatch. RhCy3 represents a direct probe for MMR-deficiency and correlates directly with the cytotoxicity of RhPPO across different cell lines. Overall, our studies clearly indicate that RhPPO and RhCy3 are promising anticancer and diagnostic probes for MMR-deficient cancers, respectively.     

Perylene-Grafted Silicas: Mechanistic Study and Applications in Heterogeneous Photoredox Catalysis

A mechanistic study is herein presented for the use of heterogeneous photocatalysts based on perylene moieties. First, the successful immobilization of perylene diimides (PDI) on silica matrices is demonstrated, including their full characterization by means of electronic microscopy, surface area measurements, powder XRD, thermogravimetric analysis, and FTIR, ²⁹Si and ¹³C solid-state NMR, fluorescence, and diffuse reflectance spectroscopies. Then, the photoredox activity of the material was tested by using two model reactions, alkene oxidation and 4-nitrobenzylbromide reduction, and mechanistic studies were performed. The mechanistic insights into their photoredox activity show they have promising dual photocatalytic activity for both organic oxidations and reductions.     

NMR of casein hydration and activity in solutions with ions

Oxygen-17 NMR studies of caseins isolated from fresh milk of several species were carried out in concentrated electrolyte solutions as a function of both protein and electrolyte concentration. Molecular dynamics simulations of ion and water binding to caseins are compared with the experimental observations by 0–17 NMR of caseins in solutions with ions. Protein activities are also determined by utilizing Wyman's theory of linked functions with a detailed model of ion binding to casein.     

Indirect atomic absorption spectrometry (IAAS) as a tool for the determination of iodide in infant formulas by precipitation of AgI and redissolution with cyanide

A method to determine iodide in infant formula samples by indirect atomic absorption spectrometry (IAAS) was developed. The iodide in solution resulting from an alkaline digestion (Na₂CO₃–NaOH) of the sample is precipitated with silver; the precipitate is redissolved by adding cyanide solution, and this solution is subjected to GF-AAS. Temperatures of 1000 and 2100°C were selected for the ashing and atomization steps, respectively, using a mixture of Pd and Mg(NO₃)₂ as a matrix modifier (at concentrations of 36 and 16 μg ml⁻¹, respectively). The sensitivity, LOD, LOQ and characteristic mass obtained were, respectively, 1.12×10⁻² l μg⁻¹, 3.1 μg g⁻¹ and 10.4 μg g⁻¹ and 7.3 pg, referred to sample. The linear interval of concentrations extends up to 10 μg l⁻¹ of iodide, with no need to use the standard addition method; the mean R.S.D. of data within this range is 3.4%, with 2.9% over the whole procedure. No interfering effects were observed among the foreign ions studied, and 100.0% was the mean analytical recovery achieved within the linear range of concentrations. The application of the method to seven real samples gave a mean content of 12.8 μg g⁻¹ of iodide, as well as less than 3.1 μg g⁻¹ in eight other samples.     

Exciplex Emission from a Boron Dipyrromethene (Bodipy) Dye Equipped with a Dicyanovinyl Appendage

The photophysical properties of a prototypic donor–acceptor dyad, featuring a conventional boron dipyrromethene (Bodipy) dye linked to a dicyanovinyl unit through a meso‐phenylene ring, have been recorded in weakly polar solvents. The absorption spectrum remains unperturbed relative to that of the parent Bodipy dye but the fluorescence is extensively quenched. At room temperature, the emission spectrum comprises roughly equal contributions from the regular π, π* excited‐singlet state and from an exciplex formed by partial charge transfer from Bodipy to the dicyanovinyl residue. This mixture moves progressively in favor of the locally excited π, π* state on cooling and the exciplex is no longer seen in frozen media; the overall emission quantum yield changes dramatically near the freezing point of the solvent. The exciplex, which has a lifetime of approximately 1 ns at room temperature, can also be seen by transient absorption spectroscopy, in which it decays to form the locally excited triplet state. Under applied pressure (P<170 MPa), formation of the exciplex is somewhat hindered by restricted rotation around the semirigid linkage and again the emission profile shifts in favor of the π, π* excited state. At higher pressure (170<P<550 MPa), the molecule undergoes reversible distortion that has a small effect on the yield of π, π* emission but severely quenches exciplex fluorescence. In the limiting case, this high‐pressure effect decreases the molar volume of the solute by approximately 25 cm³ and opens a new channel for nonradiative deactivation of the excited‐state manifold.     

Structural and electronic effects involving pyridine rings in 4-methylpyridine Cu4OX6L4 complexes. I. Vibrational spectra of Cu4OBr n Cl(6−n)(4-Mepy)4 complexes

Gaussian analysis of bands between 500 cm⁻¹ and 600 cm⁻¹ attributed to the _as (Cu₄O) stretching vibration of the tetrahedral Cu₄O core in Cu₄OBr _n Cl_(6−n)(4-Mepy)₄ (n = 0–6) complexes showed two bands, symmetry reduction of the T ₂ mode of vibration towards the A ₁ and E modes and vibrational coupling with an R-sensitive in-plane pyridine ring bending. The Cu-O bond is considered as vibrationally coupled with the Cu-N bond and the pyridine ring through the donor-acceptor vibrational coupling and the corresponding equilibrium charge distribution. The linear correlation between _as(Cu₄O) and the number of bromides in Cu₄OBr _n Cl_(6−n)(4-Mepy)₄ complexes was used for the estimation of partial charges on the 4-Mepy ligands which were positive for the prevailing donors and negative for the prevailing acceptors thus evoking a π-back bonding between the Cu(II) atoms and the 4-Mepy ligands. Correlations involving selected bond lengths and bond angles in the molecular structure of the Cu₄OCl₆(4-Mepy)₄ complex with four symmetrically independent molecules present in the unit cell indicate a symmetry reduction of the T ₂ mode of vibration and the π-back bonding between the Cu(II) atoms and the 4-Mepy ligands.     

Study of the bioavailability of selenium in cows’ milk after a supplementation of cow feed with different forms of selenium

The purpose of the work described in this paper was to develop an easy and quick in-vitro method for comparing the bioavailability of selenium in cows’ milk after different cow feed. The study focuses on bioavailability differences resulting from the use of different selenium species (organic selenium as selenised yeast and sodium selenite) for supplementation of forage. A procedure for determination of selenium in cows’ milk and dialysates, by hydride-generation atomic-fluorescence spectrometry (HG-AFS) after microwave-assisted acid digestion, was optimised. The results show it is possible to obtain cows’ milk enriched with selenium at different concentration without altering the original composition of the milk. The bioavailability was statistically greater for cows’ milk obtained after supplementation of forage with organic selenium at levels of 0.4 and 0.5 μg Se g⁻¹ than for that obtained after supplementation with inorganic and organic selenium at levels of 0.2 and 0.3 μg Se g⁻¹.     

The Influence of Temperature,Storage Conditions,pH, and Ionic Strength on the Antioxidant Activity and Color Parameters of Rowan Berry Extracts

Recent trends in the food industry combined with novel methods in agriculture could transform rowan into a valuable raw material with potential technological applications. Thus, the aim of this research was to investigate the content of bioactive compounds in its fruits and to assess the color and antioxidant stability of the extracts prepared from such fruits during various thermal treatments and at different pH and ionic strength values. Various spectrophotometric methods, HPLC, and capillary electrophoresis were used to quantify the concentrations of bioactive compounds—polyphenols, carotenoids, organic acids, and to assess antioxidant activity and color. The results show that rowan berries contain circa 1.34–1.47 g/100 g of polyphenols among which include catechin, epicatechin, ferulic acid methyl ester, procyanidin B1, etc.; ca 21.65 mg/100 g of carotenoids including zeaxanthin, β-cryptoxanthin, all-trans-β-carotene, and various organic acids such as malic, citric, and succinic, which result in a high antioxidant activity of 5.8 mmol TE/100 g. Results also showed that antioxidant activity exhibited high stability when the extract was subjected to various thermal treatments, pHs, and ionic strengths, while color was mainly impacted negatively when a temperature of 100 °C was employed. This data confirms the technological potential of this traditional, yet often overlooked species.