Bi(Pb)–Sr–Ca–Cu–O layers prepared by a new method of laser ablation in air

Bi(Pb)–Sr–Ca–Cu–O layers were prepared by laser ablation in air, that is without using a vacuum chamber. At this method a much higher density of pulse energy of laser beam is required (10–30 J cm^–2) in comparison with the standard method (1–3 J cm^–2). The mentioned condition has specific effects on the nature of the transport of material from the target. As follows from the electron microprobe analysis of the layers, the starting composition of the transported material is identical with that of the superconducting phase sintered in the target; one exception represents Pb, the content of which in the transported material is lower. The image of the process is complemented by UV/VIS spectroscopy scans of the plasma plume.     

Magnetic properties and macroscopic heterogeneity of FeCoNbB Hitperms

Nanocrystalline ribbons of Fe_81−xCo_xNb₇B₁₂ (where x ranges from 0 to 40.5 at%) Hitperm alloys have been investigated as to their basic magnetic properties and the influence of the macroscopic heterogeneity. Different crystalline share at surfaces compared with the volume average is observed by conversion electron Mössbauer spectroscopy (CEMS) and Mössbauer spectroscopy (MS), respectively. This marks the presence of macroscopic heterogeneity in these Hitperms. The heterogeneity is generally more significant in Ar-annealed samples than in the vacuum-annealed ones. The characteristic slant hysteresis loops (hard-ribbon-axis) are seen as a rule with few exceptions. An inspection of hysteresis loop response of resin potted samples shows that the surfaces bi-axially squeeze the ribbon interior in heterogeneous Hitperms when the ribbons cool down after annealing. Certain compositions show macroscopic viscous flow prior to crystallization so the heterogeneity gets another chance to induce anisotropy during annealing. The induction attains 1.5 T but saturates poorly due to the heterogeneity and the ensuing anisotropy. Moreover the heterogeneity appears to hamper the crystallization within the ribbon interior. Unlike Finemets, the density of these Hitperms show no pronounced trend with annealing.     

Influence of aggregation on interaction of lipophilic, water-insoluble azaphthalocyanines with DOPC vesicles

Dioleoylphosphatidylcholine unilamellar vesicles made by extrusion technique (LUVETs) were studied as the delivery system for lipophilic water-insoluble potential photosensitizers for photodynamic therapy (PDT). Two azaphthalocyanines (AzaPcs) with hydrophobic substituents only and two also possessing two charged amino groups were introduced into the study. All compounds are insoluble in water and form aggregates in PBS with tetrahydrofuran as cosolvent. The size of these aggregates depends on the concentration of AzaPc in solution. AzaPcs with tert-butyl substituents were found to be incorporated into the lipid bilayer of vesicles in the monomeric form even at high concentrations. The stability of LUVETs with incorporated AzaPc was excellent for at least 4 weeks. Therefore, they are suitable for use as a delivery system for these water-insoluble photosensitizers. Very low amount of AzaPc with n-octyl substituents incorporated into LUVETs due to its stronger self-aggregation. Values of binding constants determined for all AzaPcs showed inverse order than expected from their lipophilicities. However, the binding constants followed the order of the strength of aggregation forces. Aggregation of AzaPcs in water medium plays a very important role in the interaction of AzaPcs with LUVETs.     

Novel porphyrin conjugates with a potent photodynamic antitumor effect: differential efficacy of mono- and bis-beta-cyclodextrin derivatives in vitro and in vivo

In the present study we investigated the photosensitizing properties of two novel mono- and bis-cyclodextrin tetrakis (pentafluorophenyl) porphyrin derivatives in several tumor cell lines and in BALB/c mice bearing subcutaneously transplanted syngeneic mouse mammary carcinoma 4T1. Both studied sensitizers were localized mainly in lysosomes and were found to induce cell death by triggering apoptosis in human leukemic cells HL-60. In 4T1 and other cell lines both apoptotic and necrotic modes of cell death occurred depending on drug and light doses. Mono-cyclodextrin porphyrin derivative P(beta-CD)1 exhibited stronger in vitro phototoxic effect than bis-cyclodextrin derivative P(beta-CD)2. However, in vivo P(beta-CD)2 displayed faster tumor uptake with maximal accumulation 6 h after application, leading to complete and prolonged elimination of subcutaneous tumors within 3 days after irradiation (100 J cm(-2)). In contrast, P(beta-CD)1 uptake was slower (48 h) and the reduction of tumor mass was only transient, reaching the maximum at the 12 h interval when a favorable tumor-to-skin ratio appeared. Thus, P(beta-CD)2 represents a new photosensitizing drug displaying fast and selective tumor uptake, strong antitumor activity and fast elimination from the body.     

Hydrazones of 4-(Trifluoromethyl)benzohydrazide as New Inhibitors of Acetyl- and Butyrylcholinesterase

Based on the broad spectrum of biological activity of hydrazide–hydrazones, trifluoromethyl compounds, and clinical usage of cholinesterase inhibitors, we investigated hydrazones obtained from 4-(trifluoromethyl)benzohydrazide and various benzaldehydes or aliphatic ketones as potential inhibitors of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE). They were evaluated using Ellman’s spectrophotometric method. The hydrazide–hydrazones produced a dual inhibition of both cholinesterase enzymes with IC₅₀ values of 46.8–137.7 µM and 19.1–881.1 µM for AChE and BuChE, respectively. The majority of the compounds were stronger inhibitors of AChE; four of them (2-bromobenzaldehyde, 3-(trifluoromethyl)benzaldehyde, cyclohexanone, and camphor-based 2o, 2p, 3c, and 3d, respectively) produced a balanced inhibition of the enzymes and only 2-chloro/trifluoromethyl benzylidene derivatives 2d and 2q were found to be more potent inhibitors of BuChE. 4-(Trifluoromethyl)-N’-[4-(trifluoromethyl)benzylidene]benzohydrazide 2l produced the strongest inhibition of AChE via mixed-type inhibition determined experimentally. Structure–activity relationships were identified. The compounds fit physicochemical space for targeting central nervous systems with no apparent cytotoxicity for eukaryotic cell line together. The study provides new insights into this CF₃-hydrazide–hydrazone scaffold.     

Nanocrystalline alloys of Fe-Cu-Nb-Si-B after neutron irradiation

Transmission Mössbauer spectroscopy was used to study changes induced by irradiation of amorphous and nanocrystalline samples. In an as-cast sample neutrons mostly affect the orientation of a net magnetic moment. The average hyperfine field decreases towards higher neutron fluencies. In the case of the nanocrystalline samples a new disordered structure is created in the amorpous remainder corresponding to boride phases as it is shown in the samples isothermally heated from 1 to 8 hours. The structural changes of the amorphous remainder depend on the stage of crystallization and total neutron fluencies.     

Electrochemical generation of mercury cold vapor and its in-situ trapping in gold-covered graphite tube atomizers

The combination of more efficient flow-through electrochemical mercury cold vapor generation with its in-situ trapping in a graphite tube atomizer is described. This coupled technique has been optimized to attain the maximum sensitivity for Hg determination and to minimize the limits of detection and determination. A laboratory constructed thin-layer flow-through cell with a platinum cathode served as the cold vapor generator. Various cathode arrangements with different active surface areas were tested. Automated sampling equipment for the graphite atomizer with an untreated fused silica capillary was used for the introduction of the mercury vapor. The inner surface of the graphite tube was covered with a gold foil placed against the sampling hole.     

Coulometric titration of iodide and iodine with electrolytically generated hypobromite

Conditions for the quantitative coulometric titration of iodide and iodine with electrolytically generated hypobromite in the presence of borax buffer have been established. Iodide and iodine are oxidized to iodate. The method, with biamperometric indication of the equivalence point, was successfully applied for a wide range of iodide concentrations (6.21–2115μg with reliability intervals of ±0.21–±11μg) and iodine concentrations (24.26–3311μg with reliability intervals of ±0.36–±11.7μg). The determinations are accurate and sensitive even in the presence of large amounts of bromides and chlorides ($\text{Br}{}^{\mathrm{?}}\text{I}{}^{\mathrm{?}}$= 1.2·10⁶ and $\text{C}\text{l}$^?I^?=4.0·10^{3), as well as in the presence of oxidizing agents such as IO₃?, BrO₃? and CrO₄2? ($\text{I}\text{O}$₃?/I₂)=3.2·105, $\text{I}\text{O}$₃?/I₂=3.1·103, $\text{Br}\text{O}$-₃/I₂}=1.1·10⁴ and $\text{Cr}\text{O}$^2-₄/I₂=1.0·10⁴, as was confirmed by statistical tests. The oxidation mechanism under the conditions of coulometric titrations is discussed.     

Substituted pyrazinecarboxamides: synthesis and biological evaluation

Condensation of the corresponding chlorides of some substituted pyrazine-2-carboxylic acids (pyrazine-2-carboxylic acid, 6-chloropyrazine-2-carboxylic acid, 5-tert-butylpyrazine-2-carboxylic acid or 5-tert-butyl-6-chloropyrazine-2-carboxylic acid) with various ring-substituted aminothiazoles or anilines yielded a series of amides. The syntheses, analytical and spectroscopic data of thirty newly prepared compounds are presented. Structure-activity relationships between the chemical structures and the anti-mycobacterial, antifungal and photosynthesis-inhibiting activity of the evaluated compounds are discussed. 3,5-Bromo-4-hydroxyphenyl derivatives of substituted pyrazinecarboxylic acid, 16-18, have shown the highest activity against Mycobacterium tuberculosis H(37)Rv (54-72% inhibition). The highest antifungal effect against Trichophyton mentagrophytes, the most susceptible fungal strain tested, was found for 5-tert-butyl-6-chloro-N-(4-methyl-1,3-thiazol-2-yl)pyrazine-2-carboxamide (8, MIC =31.25 micromol x mL(-1)). The most active inhibitors of oxygen evolution rate in spinach Molecules 2006, 11,243 chloroplasts were the compounds 5-tert-butyl-6-chloro-N-(5-bromo-2-hydroxyphenyl)- pyrazine-2-carboxamide (27, IC(50) = 41.9 micromol x L(-1)) and 5-tert-butyl-6-chloro-N-(1,3- thiazol-2-yl)-pyrazine-2-carboxamide (4, IC50 = 49.5 micromol x L(-1)).     

Polyhydroxylated sapphyrins: multisite non-metallic catalysts for activated phosphodiester hydrolysis

Enhanced hydrolysis rates for the cleavage of bis(4-nitrophenyl)phosphate (BNPP), a model phosphodiester, may be achieved by using appropriately designed ditopic receptors containing the known phosphate-binding nucleus, sapphyrin, attached covalently to suitably oriented polyhydroxyl subunits. Evidence for the interaction between sapphyrin and BNPP comes from solid-state X-ray diffraction analysis of a diprotonated dihydroxylated sapphyrin-BNPP complex and from solution-phase (31)P NMR spectroscopic binding studies. The sapphyrins described in this paper may have a role to play as oligonucleotide cleavage agents.