Nickel and copper complexes of a chelating methacrylate sorbent in the purification of chitinases and specific immunoglobulin G1 by immobilized metal ion affinity chromatography

The isolation of the isoforms of endo- and exochitinases of Clostridium aminovalericum T1 and of the horseradish peroxidase (HRP)-specific immunoglobulin G1 from natural sources by immobilized metal ion affinity chromatography was studied. The effect of Cu2+ and Ni2+ complexes of iminodiacetic acid incorporated in porous glycidyl methacrylate-co-ethylene dimethacrylate and in agarose (Sepharose Fast Flow) beads on separation of the target polypeptides was analyzed. It was found that the Cu2+ complexes bound both the HRP-specific IgG1 and some isoforms of chitinases more strongly than the Ni2+ complexes. From the former complexes, both target polypeptides were eluted by a stepwise imidazole concentration gradient of 5-100 mM. The lower strength of Ni2+ complex binding with the HRP-specific IgG1 resulted in its easy elution with a pH gradient of 5.5-5 while some isoforms of chitinases required imidazole for their elution. The "fraction elution degree" of a target polypeptide (i.e., the ratio of its amounts in each eluate fraction and in the combined fractions) was used for the evaluation of the sorption selectivity and binding affinity of the separating components to the studied metal complexes.     

Identification of volatile aroma compounds in processed cheese analogues based on different types of fat

The simple and rapid solid-phase micro-extraction method using gas chromatography was used for the identification and quantification of volatile aroma compounds in various types of processed cheese analogues produced from different types of fat (butter, butter oil, coconut oil, palm oil, and sunflower oil). In total, 31 organic compounds belonging to five chemical groups were identified, with the alcohols and fatty acids quantitatively predominant. The contents of the aroma compounds (the so-called aroma profiles) of the analogues and corresponding fats used as raw materials were compared. Significant differences (p < 0.05) were found between samples. The highest total content of aroma compounds was found in coconut oil analogue ((547.30 ± 9.82) mg kg^?1), the lowest in palm oil analogue ((372.01 ± 16.16) mg kg^?1). The concentrations of aroma compounds in fats were substantially lower (p < 0.05) than in analogues. Hence, the largest number of aroma analogues came from Edam cheese used for production as a protein source.     

Selective Formation of Methyl α-Methylsulfanyl Dimethylphosphonothioacetate and Thiopropanoate by Phase Transfer Catalysis

The sulfanylation of methyl dimethylphosphonothioacetate was investigated by a phase transfer catalysis procedure which was shown to be superior to the noncatalytic method. The possibility of electrophilic substitution of the α-sulfanylated phosphonothioacetate to give a quaternary α-carbon atom is shown by the reaction with methyl iodide.

     

Preparation of (Pentafluorosulfanyl)benzenes by Direct Fluorination of Diaryldisulfides: Synthetic Approach and Mechanistic Aspects

Direct fluorination of ortho-, meta- and para-substituted aromatic thiols and disulfides using elemental fluorine afforded substituted (pentafluorosulfanyl)benzenes. This work thus represents the first study of the scope and limitation of direct fluorination for the synthesis of new SF₅-containing building blocks. Fluorinations in batch and flow modes were compared. A comprehensive computational study was carried out employing density functional and wave function methods to elucidate the reaction mechanism of the transformation of ArSF₃ into ArSF₅. Eliminating various nonradical pathways, it has been shown that the reaction proceeds by a radical mechanism, initiated by the attack of the F^. on the ArSF₃ moiety, propagated via an almost barrierless F₂+ArSF₄^.→ArSF₅+F^. step and terminated by the ArSF₄^.+F^.→ArSF₅. Most of the calculated data are in very good agreement with experimental observations concerning the ortho-substituent effect on the reaction rates and yields.     

Double O,C,O-chelated diorganotin(IV) derivatives

Novel diorganotin(IV) compounds (L^1,2)₂SnCl₂, where L^1,2 are O,C,O-chelating ligands (called the pincer ligands), 2,6-bis(alkoxymethyl)phenyl-, , (L¹, R = Me, L², R = t-Bu), have been synthesized and characterized by ¹H, ¹³C and ¹¹⁹Sn NMR spectroscopy, MS-ESI spectrometry and elemental analysis. The structure of both compounds (L¹)₂SnCl₂ (1) and (L²)₂SnCl₂ (2) was determined by X-ray crystallography. Determination of crystal structures reveals different shapes of coordination polyhedra. While deformed octahedron was found for 1, tetrahedral geometry of the tin atom was determined for 2. The NMR spectroscopy indicates a similar structural arrangement of 1 and 2 in solution. The reaction of 1 with silver salts of low nucleophilic anions X⁻ (X = OTf and 1-CB₁₁H₁₂) resulted in (L¹)₂SnCl(OTf) (3), (L¹)₂Sn(OTf)₂ (4), and (L¹)₂SnCl(CB₁₁H₁₂) (5). The compounds 4 and 5 are of ionic nature both in solid state and in solution of CH₃CN.     

On the asymptotic behavior of a class of third order nonlinear neutral differential equations

The objective of this paper is to study asymptotic properties of the third-order neutral differential equation

Comparison of pressurised fluid and ultrasonic extraction methods for analysis of plant antioxidants and their antioxidant capacity

The analytical method based on the high-performance liquid chromatography coupled with UV detection (HPLC/UV) for determination of selected antioxidants (i.e., esculetin, scopoletin, 7-hydroxycoumarine, rutin, xanthotoxin, 5-methoxypsoralen and quercetin) in plant material was developed. Pressurised fluid extraction (PFE) and ultrasonic extraction (USE) methods for the isolation of these compounds from ten real plant samples were used. Both extraction methods were optimised and compared to each other. For the proposed HPLC/UV method the LOQ values (limit of quantification) in the range from 22.7 (xanthotoxin) to 97.2 ng mL⁻¹ (rutin) were obtained. For all extracts the antioxidant capacity based on the reduction of free 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) was also determined. Results ranged from 82.04 to 94.43% of DPPH radical inhibition for PFE method and from 76.01 to 89.94% in the case of USE method.     

Determination of trace impurities in titanium dioxide by direct solid sampling electrothermal atomic absorption spectrometry

A true direct solid sampling electrothermal atomic absorption spectrometry method with Zeeman-effect background correction (Analytik Jena ZEEnit 60 AAS) was developed for the determination of As, Cd, Hg, Pb, Sb and Zn in powdered titanium dioxide of pharmaceutical, food and cosmetics grade. The interaction of the titanium matrix and graphite surface of the sample carrier boat in a transversely heated graphite tube atomizer was investigated. Conversion of titanium dioxide to interfering TiO₂–TiC-liquid phase, running out the sampling boat, was observed at temperatures above 2000 °C. The temperature program was optimized accordingly for these volatile analytes in atomization and cleaning steps in order to prevent this interference and to prolong significantly the analytical lifetime of the boat to more than one thousand runs. For all elements, calibration by aqueous standard addition method, by wet-chemically analyzed samples with different content of analytes and/or by dosing one sample in different amounts, were proved as adequate quantification procedures. Linear dynamic calibration working ranges can be considerably expanded up to two orders of magnitude within one measurement run by applying three-field dynamic mode of the Zeeman background correction system. The results obtained by true direct solid sampling technique are compared with those of other independent, mostly wet-chemical methods. Very low limits of detection (3σ criterion) of true solid sampling technique of 21, 0.27, 24, 3.9, 6.3 and 0.9 ng g^− 1 were achieved for As, Cd, Hg, Pb, Sb and Zn, respectively.