Five-coordinated metal complexes of bis(2-hydroxy-1-naphthylideneimine-3-propyl)amine and their reactivity towards dioxygen. Part I. An electrochemical investigation on manganese(II), iron(II), cobalt(II), nickel(II) and copper(II) complexes

The electrochemical behaviour in aprotic solvent of the complexes {M[bis-(2-hydroxy-l-naphthylideneimine-3-propyl)amine]}, where M = Mn(II), Co(II), Fe(II), Ni(II) and Cu(II) is reported. The complexes were prepared and characterized by elemental analysis, infrared and visible spectroscopy and magnetic susceptibility measurements. In addition the reactivity towards dioxygen of the Mn(II), Fe(II) and Co(II) derivatives was investigated, mainly by cyclic voltammetry and gas-volumetric uptake measurements. The results indicate that the Co(II) complexes are able to add dioxygen reversibly, while Mn(II) and Fe(II) compounds undergo an irreversible oxygenation process. The pathway of the dioxygenation processes is tentatively interpreted on the basis of the electrochemical responses. The results confirm that the location of the oxidation potential allows one to predict whether a compound is able to react with dioxygen, but it is not sufficient to predict whether the dioxygenation reaction proceeds reversibly.     

Amphiphilic porphyrin film on glass as a simple and selective solid-state chemosensor for aqueous Hg2+

Deposition of amphiphilic porphyrin derivatives occurs spontaneously on silanised glass surfaces, in a controlled fashion. The resulting porphyrin films show appreciable fluorescence emission. This emission can be effectively quenched by immersion of the slides into a diluted solution of Hg(2+) (microM concentration). The initial intensity can be restored by washings with a solution of N,N,N',N'-tetrakis(2-pyridilmethyl)ethylenediammine with no loss of efficiency. A remarkable selectivity is featured toward the detection of Hg(2+) over Cu(2+), Cd(2+), Pb(2+) and Zn(2+) counterparts. This protocol can be extended to a flow-through apparatus. The presented results are of importance for the achievement of a solid-state chemosensor for mercuric ions, at micromolar concentration, in water.     

Identification of all FK506-binding proteins from Neurospora crassa

Immunophilins are intracellular receptors of immunosuppressive drugs, carrying peptidyl-prolyl cis-trans isomerase activity, with a general role in protein folding but also involved in specific regulatory mechanisms. Four immunophilins of the FKBP-type (FK506-binding proteins) were identified in the genome of Neurospora crassa. Previously, FKBP22 has been located in the endoplasmic reticulum as part of chaperone/folding complexes and FKBP13 has been found to have a dual location in the cytoplasm and mitochondria. FKBP11 is apparently located exclusively in the cytoplasm. It is not expressed during vegetative development of the fungus although its expression can be induced with calcium and during sexual development. Overexpression of the respective gene appears to confer a growth advantage to the fungus in media containing some divalent ions. FKBP50 is a nuclear protein and its genetic inactivation leads to a temperature-sensitive phenotype. None of these proteins is, alone or in combination, essential for N. crassa, as demonstrated by the isolation of a mutant strain lacking all four FKBPs.     

Chiral separation of unmodified α-hydroxy acids by ligand exchange HPLC using chiral copper(II) complexes of (S)-phenylalaninamide as additives to the eluent

Copper(II) complexes of (S)-phenylalaninamide have been successfully used for the direct enantiomeric separation of unmodified (R,S)-α-hydroxy acids in reversed phase high-performance liquid chromatography (RP-HPLC). The effect of various parameters (pH, eluent polarity, selector concentration) on enantioselectivity is discussed. Evidence is provided that a mechanism of ligand exchange is actually occurring during the chromatographic separation. The method is very convenient and easy to use, and the chiral selector is commercially available and can be recovered at the end of the analysis. A conventional achiral RP-ODS-2 column is used and no pretreatment of the samples is required. This method allows the accurate determination of the enantiomeric excess of α-hydroxy acids in synthetic and biological samples. © 1995 Wiley-Liss, Inc.     

Evaluation of the Auxacolor system for the identification of clinical yeast isolates

In the last decade the number of systemic yeast infections has increased significantly. Although Candida albicans is the most frequently isolated yeast from clinical specimens, the emergence of non-albicans species has clearly been a recent concern. As a consequence, there is a greater need for rapid and accurate methods for yeast identification. The aim of this study was to evaluate the performance of the AUXACOLOR system (Sanofi Diagnostics Pasteur) for the identification of clinically relevant yeasts, as compared with the conventional method. Yeast isolates (n = 97) belonging to 12 species were identified by the commercial system and the classic method. Correct identifications were obtained by using AUXACOLOR system in 79.4% of the isolates tested. Misidentification occurred in 5.2% of the strains and 15.5% were not identified due to a failure in the manufacturer's data base. In order to improve its accuracy, there is a need for expanding the database or revamping the tests included in the system. This revised version was published online in June 2006 with corrections to the Cover Date.     

Enolase from Streptococcus sobrinus is an immunosuppressive protein

A strategy of Streptococcus sobrinus, a major agent of dental caries, to survive and colonize the host consists of the production of a protein that suppresses the specific antibody responses. We have cloned the gene coding for a protein with immunosuppressive activity. It contains an open reading frame of 1302 base pairs encoding a polypeptide with 434 amino acid residues and a molecular mass of 46910 Da. The gene product is homologous to enolases from several organisms. The polypeptide was expressed in Escherichia coli as a hexahistidine-tagged protein and purified in a fluoride-sensitive enzymatically active form. Pretreatment of mice with the S. sobrinus recombinant enolase suppresses a primary immune response against T-cell dependent antigens. This immunosuppressive effect is specific to the antigen used in the immunization, as it is not observed when the immune response against other antigens is analysed. Furthermore, the S. sobrinus recombinant enolase stimulates an early production of interleukin-10, an anti-inflammatory cytokine, and not the pro-inflammatory cytokine IFN-gamma. These observations indicate that enolase acts in the suppression of the specific host immune response against S. sobrinus infection.     

Calcium Oxalate Crystals in Eucalypt Ectomycorrhizae: Morphochemical Characterization

Ectomycorrhizal fungi are ubiquitous in forest ecosystems, benefitting plants principally by increasing the uptake of water and nutrients such as calcium from the soil. Previous work has demonstrated accumulation of crystallites in eucalypt ectomycorrhizas, but detailed morphological and chemical characterization of these crystals has not been performed. In this work, cross sections of acetic acid-treated and cleared ectomycorrhizal fragments were visualized by polarized light microscopy to evaluate the location of crystals within cortical root cells. Ectomycorrhizal sections were also observed by scanning electron microscopy (SEM) coupled with energy dispersive x-ray (EDS) microprobe analysis. The predominant forms of crystals were crystal sand (granules) and concretions. Calcium, carbon and oxygen were detected by EDS as constituent elements and similar elemental profiles were observed between both crystal morphologies. All analyzed crystalline structures were characterized as calcium oxalate crystals. This is the first report of the stoichiometry and morphology of crystals occurring in eucalypt ectomycorrhizas in tropical soils. The data corroborates the role of ectomycorrhizae in the uptake and accumulation of calcium in the form of calcium oxalate crystals in hybrid eucalypt plants.     

Arabidopsis Synaptotagmin 1 Is Required for the Maintenance of Plasma Membrane Integrity and Cell Viability

Plasma membrane repair in animal cells uses synaptotagmin 7, a Ca²⁺-activated membrane fusion protein that mediates delivery of intracellular membranes to wound sites by a mechanism resembling neuronal Ca²⁺-regulated exocytosis. Here, we show that loss of function of the homologous Arabidopsis thaliana Synaptotagmin 1 protein (SYT1) reduces the viability of cells as a consequence of a decrease in the integrity of the plasma membrane. This reduced integrity is enhanced in the syt1-2 null mutant in conditions of osmotic stress likely caused by a defective plasma membrane repair. Consistent with a role in plasma membrane repair, SYT1 is ubiquitously expressed, is located at the plasma membrane, and shares all domains characteristic of animal synaptotagmins (i.e., an N terminus-transmembrane domain and a cytoplasmic region containing two C2 domains with phospholipid binding activities). Our analyses support that membrane trafficking mediated by SYT1 is important for plasma membrane integrity and plant fitness.     

Polyamine biosynthesis in rabbit perfused heart under various degrees of oxygen tension

Ornithine decarboxylase and S-adenosylmethionine decarboxylase activities increase in hypoxic perfused rabbit heart (more with less severe hypoxia). Anoxic perfusion causes a decrease in the former activity and no effect in the latter. Changes in polyamine specific radioactivity are consistent with those of the the two enzymes, except for the enhancement at 60 minutes of anoxia.