Reference material “total protein in human urine”

Two batches of a reference material (RM) “total protein in human urine” were prepared for quality assurance in the determination of human urinary proteins. The material was prepared by freeze-drying of a pooled urine sample obtained from healthy volunteers. Protein concentrations in both batches were within physiological values, close to their upper limit. Interlaboratory comparisons conducted in 26 laboratories using the standard operation procedures elaborated for six of the most frequently employed methods (biuret, Bradford, Exton, Lowry, Pesce, and Watanabe) revealed that the results obtained by the individual methods were significantly different due to various reaction mechanisms involved. It was therefore necessary to certify the mean values and their uncertainties individually for each method. These operationally defined certified or information values are valid only when the prescribed standard operation procedures are strictly followed.     

1-Naphthols as components for multifunctional material systems (MFMS): the molecular modeling approach

Structural Chemistry - Increasing research interests have been paid to developing efficient multifunctional material systems (MFMS) by using various composite materials, owing to their useful...     

Easy and efficient deracemization of all trans-1,3-diphenyl-2,4-bis-[α-hydroxybenzyl]-cyclobutane and its bisphenylsulfanyl derivative and the assignment of the absolute configuration

An effective deracemization of all trans-1,3-diphenyl-2,4-bis-[α-hydroxybenzyl]-cyclobutane 1 was achieved by the application of the (R)-(?)-O-acylmandelic acid as a resolving agent, followed by the crystallization of the diastereomeric esters. The kinetic resolution was also observed in the esterification. Racemic 1 was transformed into bisphenylsulfanyl derivative 3. Enantioselective oxidation of 3 with a VO(acac)₂-chiral Schiff Base catalytic system led to a kinetic resolution, and highly enantiomerically enriched bissulfides/bissulfoxides were isolated. Assignment of the absolute configuration was made by spectroscopic methods and chemical correlation. Due to the rigid C₂-symmetric framework, chiral compounds 1 and 3 have strong steric requirements and may be useful in chiral recognition.     

Aziridine-2-carboxylic acid derivatives and its open-ring isomers as a novel PDIA1 inhibitors

Chemistry of Heterocyclic Compounds - Acyl derivatives of aziridine-2-carboxylic acid have been synthesized and tested as PDIA1 inhibitors. Calculations of charge value and distribution in...     

Dielectric properties and thermal stability of γ-irradiated inorganic nanofiller modified PVC

The dielectric characteristics of polyvinyl chloride nanocomposites containing titania, silica and alumina at the concentration of 5% were investigated by dielectric spectroscopy. The sharp modification in the permittivity and dielectric loss of neat and irradiated PVC samples over the low frequency range may be explained by the interaction between external electrical field and the dipoles formed during high energy exposure. The material characterization is completed by the thermal stability assay based on the accumulation of carbonyl units in the sample matrices, which provides the differences in the molecular level contact between host polymer and fillers.     

The effect of different workplace nanoparticles on the immune systems of employees

Currently, nanoparticles are widely present in the environment and are being used in various industrial technologies. Nanoparticles affect immune functions, causing different immune responses. The aim of the current study was to evaluate several cytokines, interleukin (IL)-1b, IL-6, IL-8, tumour necrosis factor-a (TNF-α), interferon-γ, adhesive molecule sICAM-1, macrophage inhibitory protein 1a (MIP1a) and secretory immunoglobulin A, in nasal lavage fluid and in the peripheral blood of healthy subjects exposed to workplace nanoparticles. Thirty-six employees from three different environments were examined: 12 from a metalworking company, 12 from a woodworking company and 12 office workers. The nanoparticles in the different workplaces were detected in the air in the immediate vicinity of the employees. The particle number concentration and surface area values were significantly higher in the workplaces of the metal- and woodworking industries, but concentrations of mass were lower (the measurements were performed by an electrical low-pressure impactor ELPI+). Energy dispersive X-ray spectroscopy (EDS, an attachment to a high-resolution SEM) was used to provide elemental analysis or chemical characterization of the dust particles in a low-vacuum field-free mode operating at a potential of 15 kV spot 3.0. The technique used provided quantitative and spatial analyses of the distribution of elements through mapping (two to three parallel measurements) and point analysis (four to five parallel measurements). Samples from the metal industry contained more ultramicroscopic and nanometric particles, e.g. toxic metals such as Zn, Mn and Cr, and fewer microscopic dust particles. The nasal lavage and peripheral blood were taken at the beginning and the end of the working week, when immune indices were measured. Our data showed a statistically significant increased level of the pro-inflammatory cytokine TNF-α in serum in both exposed groups compared with office workers as well as a higher level of TNF-α in workers from the woodworking company compared with the metalworking employees. We found an elevated level of IL-6 in the exposed groups as well as an elevated level of IL-8 in the nasal lavage in woodworking employees after work.     

The crystal and molecular structure of sodium 4‐(2,4,6‐triisopropylbenzoyl)benzoate in terms of the photochemical behaviour of the anion

Contrary to the known 4‐(2,4,6‐triisopropylbenzoyl)benzoate salts, di‐μ‐aqua‐bis[tetraaquasodium(I)] bis[4‐(2,4,6‐triisopropylbenzoyl)benzoate] dihydrate, [Na₂(H₂O)₁₀](C₂₃H₂₇O₃)₂·2H₂O, (1), does not undergo a photochemical Norrish–Yang reaction in the crystalline state. In order to explain this photochemical inactivity, the intermolecular interactions were analyzed by means of the Hirshfeld surface and intramolecular geometrical parameters describing the possibility of a Norrish–Yang reaction were calculated. The reasons for the behaviour of the title salt are similar crystalline environments for both the o‐isopropyl groups in the anion, resulting in similar geometrical parameters and orientations, and that these interaction distances differ significantly from those found in salts where the photochemical reaction occurs.     

Crystal Structures of N-(4-butyryl-3-hydroxyphenyl)acetamide Monohydrate and 4-(4-Chlorophenyl)-2-methyl-4-oxobutanoic Acid: Possibilities of Yang Photocyclization

Abstract  

N-(4-butyryl-3-hydroxyphenyl)acetamide monohydrate, (I), and 4-(4-chlorophenyl)-2-methyl-4-oxobutanoic acid, (II), are photochemically inert, which is a result of their conformation. The geometrical parameters describing the molecular conformation and possibilities of the Yang photocyclization in crystals have been calculated and discussed. Compound (I) forms double ribbons along the a axis, stabilized by hydrogen bonds and π⋯π interactions. Compound (II) forms dimers. (I): triclinic, space group \textP[`1] {\text{P}}\bar{1} , a = 6.9291(12) ?, b = 7.5736(16) ?, c = 13.0528(18) ?, α = 79.643(17)°, β = 85.818(15)°, γ = 63.97(2)°, Z = 2. (II): monoclinic, space group P2₁/c, a = 11.904(2) ?, b = 9.6508(12) ?, c = 10.666(2) ?, β = 110.64(2)°, Z = 4.     

Rapid RP-LC Method with Fluorescence Detection for Analysis of Fexofenadine in Human Plasma

A rapid and sensitive reversed-phase high-performance liquid chromatographic method for analysis of fexofenadine in human plasma has been developed and optimized. The analytes were extracted from biological samples by solid-phase extraction on hydrophilic–lipophilic balance cartridges. LC separation was performed on a C₁₈ analytical column (125 mm × 4 mm i.d., 5-μm particles) with 42:58 (v/v) acetonitrile–water adjusted to pH 2.7 with 85% orthophosphoric acid as mobile phase. Fluorescence detection was performed with excitation at 230 nm and emission at 290 nm. The total time for chromatographic separation was 7 min. The method was validated in accordance with EU guidelines by analysis of plasma samples fortified with fexofenadine at concentrations between 0.05 and 800 ng mL^?1. Calibration plots were linear in this range. Mean recovery was typically 94.03% and the detection limit was 0.05 ng mL^?1. The time required for quantitative analysis is shorter than that required by other methods.