Value of apoptin’s 40-amino-acid C-terminal fragment for the differentiation between human tumor and non-tumor cells

Apoptin, a protein of the chicken anemia virus (CAV), consists of 121 amino acids (aa) and represents a novel, potentially tumor-specific therapeutic and diagnostic agent. The C-terminal part of Apoptin (aa 81–121) is believed to contain a bipartite nuclear localization signal (NLS) (NLS1: aa 82–88 and NLS2: aa 111–121), which is only active in tumor cells after phosphorylation of threonine¹⁰⁸ by tumor-specific cytoplasmic phosphokinases. Furthermore, a nuclear export signal (NES) (aa 97–105) seems to enable nuclear export of Apoptin only in healthy cells. The specificity for tumor cell nuclei also applies to the truncated C-terminal part of Apoptin (aa 81–121), which therefore represents a highly attractive peptide sequence for peptide synthesis. Here we describe for the first time the synthesis of fluorescein isothiocyanate (FITC)- and Dansyl-labelled conjugates containing this C-terminal part of Apoptin, with either phosphorylated or nonphosphorylated threonine¹⁰⁸. The phosphorylated conjugates were synthesized in an attempt to achieve nuclear accumulation in healthy cells, which lack cytoplasmic tumor-specific phosphokinases. Surprisingly, all the conjugates accumulated rapidly within the cell nuclei of both tumor and non-tumor cells from the bladder, brain and prostate and led to cell death. By coupling Apoptin^81–121 to FITC and DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) at either the C- or N-terminus we could exlude that the coupling site is decisive for tumor cell-specific nuclear localization. The labels FITC, DOTA and Dansyl were not responsible for cell death in healthy cells because cell death was not prevented by using an unlabelled Apoptin^81–121 peptide. Cellular and nuclear uptake of the FITC-labelled Apoptin^81–121 peptide was almost completely abolished after altering the NLS2 (replacement of five arginines with serines).     

2-Hydroxyphenacyl azoles and related azolium derivatives as antifungal agents

2-Hydroxyphenacyl azole and 2-hydroxyphenacyl azolium compounds have been described as a new class of azole antifungals. Most target compounds showed significant in vitro antifungal activities against tested fungi (Candida albicans, Saccharomyces cerevisiae, Aspergillus niger, and Microsporum gypseum) with low MICs values included in the range of 0.25-32 microg/mL comparable to reference drug fluconazole. The most active compounds were also assessed for their cytotoxicity using MTT colorimetric assay on normal mouse fibroblast (NIH/3T3) cells. The results of antifungal activity and toxicity tests indicated that these compounds display antifungal activity at non-cytotoxic concentrations.     

Comparison of thermochemistry of aspartame (artificial sweetener) and glucose

We have compared the gas phase thermochemical properties of aspartame (artificial sweetener) and α- and β-glucose. These parameters include metal ion affinities with Li⁺-, Na⁺-, K⁺-, Mg⁺²-, Ca⁺²-, Fe⁺²-, Zn⁺²-ions, and chloride ion affinity by using DFT calculations. For example, for aspartame, the affinity values for the above described metal ions are, respectively, 86.5, 63.2, 44.2, 255.4, 178.4, 235.4, and 300.4, and for β-glucose are 65.2, 47.3 32.9, 212.9, 140.2, 190.1, and 250.0 kcal mol⁻¹, respectively. The study shows differences between the intrinsic chemistry of aspartame and glucose.     

Sonochemical synthesis of nano-sized metal-organic lead(II) polymer: A precursor for the preparation of nano-structured lead(II) iodide and lead(II) oxide

Nanoparticles of a new Pb^II metal-organic polymer, [Pb(μ-pyr)(μ-I)₂]_n (1), with a net-like morphology have been synthesized by the reaction of pyrazine with Pb(NO₃)₂ and NaI via sonochemical irradiation. Nano-structured PbI₂ and PbO were synthesized from compound 1 by calcination at argon and air atmospheres, respectively. The structure of 1 was determined by single crystal X-ray crystallography and the nano-structures were characterized by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). The thermal stability of nano-sized and single crystalline samples of 1 were studied and compared.     

Phage Shock Protein G,a Novel Ethanol-Induced Stress Protein in <Emphasis Type="Italic">Salmonella typhimurium</Emphasis>

Exposure to ethanol is a stress condition that Salmonella typhimurium often encounters during its life cycle. Food, beverage, drugs, and cosmetics have a long history of using alcohols to control pathogens. Ethanol is also commonly used for disinfecting medical instruments. This study was conducted to evaluate the ethanol stress variations on the protein profile, cell structure, and serologic features of S. typhimurium. Sodium dodecyl sulfate–polyacrylamide gel electrophoresis revealed the phage shock protein G (pspG), a new ethanol-induced stress protein in cells adapted to 10% ethanol. The result was confirmed by liquid chromatography–mass spectrometry. The maximum quantity of this 9.02-kDa protein was produced in 12.5% (v/v) of ethanol-treated cultures. Scanning electron microscopy has demonstrated new phenotypic characteristics in bacterial structure. The cells were unable to undergo binary fission. This phenomenon explains the tight attachment of bacteria in a colony. Overall, ethanol extreme stress induced expression of new proteins like PspG and repression of some other proteins in S. typhimurium. These induction and repression processes have inflicted dramatic changes on Salmonella behaviors. Alireza Shoae Hassani, Kasra Hamdi and Amir Ghaemi are members of Young Researchers Club (YRC) of Tehran Science & Research Campus of IAU, Tehran, Iran.     

The mechanism of specific binding of free cholesterol by the steroidogenic acute regulatory protein: evidence for a role of the C-terminal alpha-helix in the gating of the binding site

Steroidogenesis depends on the delivery of free cholesterol to the inner mitochondrial membrane by StAR (steroidogenic acute regulatory protein). Mutations in the StAR gene leads to proteins with limited cholesterol-binding capacity. This gives rise to the accumulation of cytoplasmic cholesterol, a deficit in steroid hormone production and to the medical condition of lipoid congenital adrenal hyperplasia. A detailed understanding of the mechanism of the specific binding of free cholesterol by StAR would be a critical asset in understanding the molecular origin of this disease. Previous studies have led to the proposal that the C-terminal alpha-helix 4 of StAR was undergoing a folding/unfolding transition. This transition is thought to gate the cholesterol-binding site. Moreover, a conserved salt bridge (Glu169-Arg188) in the cholesterol-binding site is also proposed to be critical to the binding process. Interestingly, some of the documented clinical mutations occur at this salt bridge (E169G, E169K and R188C) and in the C-terminal alpha-helix 4 (L275P). In the present study, using rationalized mutagenesis, activity assays, CD, thermodynamic studies and molecular modelling, we characterized the alpha-helix 4 mutations L271N and L275P, as well as the salt bridge double mutant E169M/R188M. The results provide experimental validation for the gating mechanism of the cholesterol-binding site by the C-terminal alpha-helix and the importance of the salt bridge in the binding mechanism. Altogether, our results offer a molecular framework for understanding the impact of clinical mutations on the reduction of the binding affinity of StAR for free cholesterol.     

Proposal of Xanthomonas translucens pv. pistaciae pv. nov., pathogenic to pistachio (Pistacia vera)

Strains of Xanthomonas translucens have caused dieback in the Australian pistachio industry for the last 15 years. Such pathogenicity to a dicotyledonous woody host contrasts with that of other pathovars of X. translucens, which are characterized by their pathogenicity to monocotyledonous plant families. Further investigations, using DNA-DNA hybridization, gyrB gene sequencing and integron screening, were conducted to confirm the taxonomic status of the X. translucens pathogenic to pistachio. DNA-DNA hybridization provided a clear classification, at the species level, of the pistachio pathogen as a X. translucens. In the gyrB-based phylogeny, strains of the pistachio pathogen clustered among the X. translucens pathovars as two distinct lineages. Integron screening revealed that the cassette arrays of strains of the pistachio pathogen were different from those of other Xanthomonas species, and again distinguished two groups. Together with previously reported pathogenicity data, these results confirm that the pistachio pathogen is a new pathovar of X. translucens and allow hypotheses about its origin. The proposed name is Xanthomonas translucens pv. pistaciae pv. nov.     

Aggregation and Amyloid Fibril Formation Induced by Chemical Dimerization of Recombinant Prion Protein in Physiological-like Conditions

Prion diseases are caused by the conversion of a cellular protein (PrP^C) into a misfolded, aggregated isoform (PrP^Res). Misfolding of recombinant PrP^C in the absence of PrP^Res template, cellular factors, denaturing agents, or at neutral pH has not been achieved. A number of studies indicate that dimerization of PrP^C may be a key step in the aggregation process. In an effort to understand the molecular event that may activate misfolding of PrP^C in more relevant physiological conditions, we tested if enforced dimerization of PrP^C may induce a conformational change reminiscent of the conversion of PrP^C to PrP^Res. We used a well described inducible dimerization strategy whereby a chimeric PrP^C composed of a modified FK506-binding protein (Fv) fused with PrP^C and termed Fv-PrP is incubated in the presence of a monomeric FK506 or dimerizing AP20187 ligand. Addition of AP20187 but not FK506 to recombinant Fv-PrP (rFv-PrP) in physiological-like conditions resulted in a rapid conformational change characterized by an increase in β-sheet structure and simultaneous aggregation of the protein. Aggregates were partially resistant to proteinase K and induced the conversion of soluble rFv-PrP in serial seeding experiments. As judged from thioflavin T binding and electron microscopy, aggregates converted to amyloid fibers. Aggregates were toxic to cultured cells, whereas soluble rFv-PrP and amyloid fibers were harmless. This study strongly supports the proposition that dimerization of PrP^C is a key pathological primary event in the conversion of PrP^C and may initiate the pathogenesis of prion diseases.     

Synthesis and dopaminergic activity of some E-3-(piperidin-1-yl)-1-(4-substituted phenyl)prop-2-en-1-one derivatives

A convenient route for the synthesis of some 2-propen-1-one derivatives with E isomeric configuration is described. The activity of the synthesized compounds was evaluated through behavioral studies of apomorphine-induced licking in animal models. It was demonstrated that most of the synthesized compounds showed moderate activity in inhibition of lickings, among which 6a, was the most active compound at 30 mg/kg.