The role of phytochelatins in Sinapis alba L. response to stress caused by two toxic elements As and Tl

Phytochelatins (PCs) play an important role in the detoxification and homeostasis processes in plants, since xenobiotics complexed by sulfhydryl groups are less toxic than the free ions. This paper describes studies related to PCs synthesis in Sinapis alba L. exposed to As and Tl salts, and in particular to the identification of the PC complexes that are formed in white mustard tissues. To reach the goal, two analytical methods were applied – high-performance liquid chromatography with fluorescent detection analysis after derivatisation of thiol compounds and high-performance liquid chromatography with electrospray ionization mass spectrometry (HPLC ESI MS). The study confirmed the synthesis of PCs in all plant organs under the influence of As salt. Moreover two As-PC complexes were identified: As-PC₃ and As-PC₄. While in the case of Tl – although that element strongly influenced the growth of Sinapis alba L. and to a great extent was transported to above-ground organs – no PC complexes or free PCs were found in plants exposed to Tl salt. Although both elements exist in mustard plant tissues at their trivalent oxidation state, showing high affinity to thiol groups, a defence mechanism associated with the synthesis of PC occurred only in case of arsenic.     

Multiband Transport in CoSb3 Prepared by Rapid Solidification

Nano‐grained CoSb₃ was prepared by melt‐spinning and subsequent spark plasma sintering. The phonon thermal conductivity of skutterudites is known to be sensitive to the kind and the amount of guest atoms. Thus, unfilled CoSb₃ can serve as model compound to study the impact of a nanostructure on the thermoelectric properties, especially the phonon thermal conductivity. Therefore, a series of materials was prepared differing only by the cooling speed during the quenching procedure. In contrast to clathrates, the microstructure of meltspun CoSb₃ was found to be sensitive to the cooling speed. Although the phonon thermal conductivity, studied by means of Flash and 3ω measurements, was found to be correlated with the grain size, the bulk density of the sintered materials had an even stronger impact. Interestingly, the reduced bulk density did not result in an increased electrical resistivity. The influence of Sb and CoSb₂ as foreign phase on the electronic properties of CoSb₃ was revealed by a multi‐band Hall effect analysis. While CoSb₂ increases the charge carrier density, the influence of the highly mobile charge carriers introduced by elemental Sb on the thermoelectric properties of the composite offer an interesting perspective for the preparation of efficient thermoelectric composite materials.     

Spheroid cultivation of HT-29 carcinoma cell line in liquid marbles

The ability to simulate the 3D structure of a human body is essential to increase the efficiency of drug development. In vivo conditions are significantly different in comparison to in vitro conditions. A standardly used cell monolayer on tissue culture plastic (2D cell culture) is not sufficient to simulate the transfer phenomena occurring in living organisms, therefore, cell growth in a 3D space is desired. Drug absorption, distribution, metabolism, excretion and toxicity could be tested on 3D cell aggregates called spheroids, decrease the use of animal models and accelerate the drug development. In this work, the formation of spheroids from HT-29 human colorectal adenocarcinoma cells was successfully achieved by means of the so-called liquid marbles, which are liquid droplets encapsulated by a hydrophobic powder. During the cultivation in the medium inside the liquid marbles, cells spontaneously formed spherical agglomerates (spheroids) without the need of any supporting scaffold. The study focused on the influence of different parameters—namely liquid marble volume, seeding cell density and time of cultivation—on the final yield and quality of spheroids. This work has shown that using liquid marbles as microbioreactors is a suitable method for the cultivation of HT-29 cells in the form of spheroids.     

Enantioselective analysis of ketamine and its metabolites in equine plasma and urine by CE with multiple isomer sulfated beta-CD

CE with multiple isomer sulfated beta-CD as the chiral selector was assessed for the simultaneous analysis of the enantiomers of ketamine and metabolites in extracts of equine plasma and urine. Different lots of the commercial chiral selector provided significant changes in enantiomeric ketamine separability, a fact that can be related to the manufacturing variability. A mixture of two lots was found to provide high-resolution separations and interference-free detection of the enantiomers of ketamine, norketamine, dehydronorketamine, and an incompletely identified hydroxylated metabolite of norketamine in liquid/liquid extracts of the two body fluids. Ketamine, norketamine, and dehydronorketamine could be unambiguously identified via HPLC fractionation of urinary extracts and using LC-MS and LC-MS/MS with 1 mmu mass discrimination. The CE assay was used to characterize the stereoselectivity of the compounds' enantiomers in the samples of five ponies anesthetized with isoflurane in oxygen and treated with intravenous continuous infusion of racemic ketamine. The concentrations of the ketamine enantiomers in plasma are equal, whereas the urinary amount of R-ketamine is larger than that of S-ketamine. Plasma and urine contain higher S- than R-norketamine levels and the mean S-/R-enantiomer ratios of dehydronorketamine in plasma and urine are lower than unity and similar.     

Determination of the cation-chelating potential of C-methylthiolated beta-lactams and their sulfones by electrospray ionization mass spectrometry

The chelation potential of highly lipophilic C-dimethylthiolated monocyclic beta-lactams was examined using electrospray ionization mass spectrometry (ESI-MS). The metal salts NaCl, KCl, CaCl2, ZnCl2, Cu(NO3)2, CdSO4, MnCl2, and Mg(NO3)2 were used for the analysis. The K+ adducts of the compounds studied were more responsive in ESI analysis, compared to their Na+ adducts, regardless of the oxidation state of the sulfur (in the methylthio or the sulfone groups) and the type of the group adjacent to the lactam carbonyl. Opening of the beta-lactam ring, leading to formation of a chargeable N-atom, had little to no effect on the K+ adduct formation. Interactions of the methylthio group with the divalent zinc ion were also observed.     

Aggregates of naphthalene chromophores in poly(vinylalcohol)-graft-poly(vinylnaphthalene) pseudomicelles

A novel amphiphilic grafted copolymer, poly(vinylalcohol)-graft-poly(vinylnaphthalene), was synthesized and studied spectroscopically. The unusual photophysical properties of its aqueous solutions were observed for the first time and are attributed to the aggregation of the naphthalene chromophores in the bulk of polymer pseudomicelles. The enormous red shift of the fluorescence spectra is interpreted in terms of the confinement effect. The interpretation is supported by model calculations, taking into account the mixing of Frenkel excitons and charge-transfer states of chromophore clusters in densely packed polymer domains. Gradual funneling of the excitation energy between aggregates of different sizes is discussed in the context of the measured fluorescence depolarization spectra.