Case Study of Polyvinylidene Fluoride Doping by Carbon Nanotubes.

Modern material science often makes use of polyvinylidene fluoride thin films because of various properties, like a high thermal and chemical stability, or a ferroelectric, pyroelectric and piezoelectric activity. Fibers of this polymer material are, on the other hand, much less explored due to various issues presented by the fibrous form. By introducing carbon nanotubes via electrospinning, it is possible to affect the chemical and electrical properties of the resulting composite.

Influence of Hydroxyapatite Nanoparticles and Surface Plasma Treatment on Bioactivity of Polycaprolactone Nanofibers.

Nanofibers are well known as a beneficial type of structure for tissue engineering. As a result of the high acquisition cost of the natural polymers and their environmentally problematic treatment (toxic dissolution agents), artificial polymers seem to be the better choice for medical use. In the present study, polycaprolactone nano-sized fibrous structures were prepared by the electrospinning method.

Structure-Properties Relationship of Electrospun PVDF Fibers.

Electrospinning as a versatile technique producing nanofibers was employed to study the influence of the processing parameters and chemical and physical parameters of solutions on poly(vinylidene fluoride) (PVDF) fibers' morphology, crystallinity, phase composition and dielectric and piezoelectric characteristics. PVDF fibrous layers with nano- and micro-sized fiber diameters were prepared by a controlled and reliable electrospinning process. The fibers with diameters from 276 nm to 1392 nm were spun at a voltage of 25 kV-50 kV from the pure PVDF solutions or in the presence of a surfactant-Hexadecyltrimethylammonium bromide (CTAB).

Synthesis of deuterium labeled NMDA receptor inhibitor - 20-Oxo-5β-[9,12,12-(2)H(3)]pregnan-3α-yl-L-glutamyl 1-ester.

20-Oxo-5β-[9,12,12-(2)H(3)]pregnan-3α-yl-l-glutamyl 1-ester 11 was synthesized as an internal standard for quantification of a neuroprotective NMDA receptor ligand, 20-oxo-5β-pregnan-3α-yl-l-glutamyl 1-ester 18 and its metabolites, in plasma and tissue. 11α-Hydroxy-progesterone (1) was reduced under basic conditions to yield the corresponding 5β-steroid. Protection of the 3- and 20-oxo groups and oxidation of the 11α-hydroxy group was then followed by a deuterium exchange, conducted under basic conditions using deuterated methanol.

Access of inhibitory neurosteroids to the NMDA receptor.

Background And Purpose: NMDA receptors are glutamatergic ionotropic receptors involved in excitatory neurotransmission, synaptic plasticity and excitotoxic cell death. Many allosteric modulators can influence the activity of these receptors positively or negatively, with behavioural consequences. 20-Oxo-5β-pregnan-3α-yl sulphate (pregnanolone sulphate; PA-6) is an endogenous neurosteroid that inhibits NMDA receptors and is neuroprotective.

The use of symmetry in enantioselective synthesis: four pairs of chrysene enantiomers prepared from 19-nortestosterone.

Expansion of the D-ring of 19-norsteroids with incorporation of the steroid C-18 methyl group into a newly formed six-membered ring provides easy access to the chrysene ring system. By taking advantage of the symmetry of the chrysene ring system and avoiding meso chrysene intermediates, four optically pure 2,8-difunctionalized (C-2 hydroxyl group and C-8 oxo group) hexadecahydrochrysene diastereomers, and their corresponding optically pure enantiomers were prepared from 19-nortestosterone. The eight chrysene stereoisomers are of interest as starting materials for preparing chrysene analogues of physiologically important neurosteroids.

Neurosteroid analogues. 16. A new explanation for the lack of anesthetic effects of δ(16)-alphaxalone and identification of a δ(17(20)) analogue with potent anesthetic activity.

This study addresses the hypothesis that the lack of anesthetic activity for (3α,5α)-3-hydroxypregn-16-ene-11,20-dione (Δ(16)-alphaxalone) is explained by the steroid Δ(16) double bond constraining the steroid 20-carbonyl group to a position that prevents it from favorably interacting with γ-aminobutyric acid type A (GABA(A)) receptors. A series of Δ(16) and Δ(17(20)) analogues of Δ(16)-alphaxalone was prepared to evaluate this hypothesis in binding, electrophysiological, and tadpole anesthesia experiments. The results obtained failed to support the hypothesis.

Stereoselectivity of sodium borohydride reduction of saturated steroidal ketones utilizing conditions of Luche reduction.

A series of keto steroids were reduced with sodium borohydride in the presence of cerium(III) chloride or samarium(III) iodide (Luche reduction). The ratios of axial and equatorial alcohols were determined by HPLC and the results were compared with those obtained by a standard sodium borohydride reduction. The best results were obtained with the 2-keto derivative 1, 7-keto derivatives 5 and 6, and 12-keto derivative 8 where the cerium(III) ion addition resulted in the inversion of the axial/equatorial ratios.

Synthesis of fluorinated brassinosteroids based on alkene cross-metathesis and preliminary biological assessment.

Three types of brassinosteroid analogues with perfluoroalkylated side chains were synthesized by using alkene cross-metathesis of a brassinosteroid derivative bearing a terminal alkene moiety with different (perfluoroalkyl)propenes. The presence of the double bonds in the cross-metathesis products allowed a facile one-step double dihydroxylation to provide intermediates that after Baeyer-Villiger oxidation afforded the target compounds. Biological activity of the prepared analogues was tested in GABA(A) receptor, cytotoxic, and brassinolide activity, which reached in some cases the same range as their nonfluorinated analogues.

Synthesis of C3, C5, and C7 pregnane derivatives and their effect on NMDA receptor responses in cultured rat hippocampal neurons.

The synthesis of several novel 5alpha- and 5beta-20-oxo-pregnane derivatives substituted in the position 3 and 7 of the steroid skeleton is described. Activity of synthesized compounds was studied in voltage-clamped cultured rat hippocampal neurons. Substituted derivatives inhibited NMDA-elicited neuronal activity.

[Prevalence of ESBL-positive strains of Klebsiella pneumoniae in the Czech Republic and their molecular biology analysis].

Background: One of the problems of contemporary medicine is an increasing number of bacterial strains with hazardous phenotypes of resistance. The feared bacterial pathogens include Klebsiella pneumoniae strains producing AmpA extended-spectrum beta-lactamases. The study focused on the molecular biological characteristics of ESBL-positive strains of Klebsiella pneumoniae collected in the Czech Republic.