Complexation of 3,4-hydroxypyridinecarboxylic acids with Iron(III)

The chemical interactions of 3-hydroxy-4-pyridinecarboxylic acid (3H4P) and 4-hydroxy-3-pyridinecarboxylic acid (4H3P) with Fe(III) were investigated in aqueous 0.6 m (Na)Cl at 25 °C by means of potentiometric titrations and UV-Vis spectrophotometry. A large number of mononuclear complexes were formed in solution; one of the Fe/3H4P species was obtained as a solid and characterised by elemental analysis. In view of a possible application to iron(III) chelation therapy, the efficiencies of the ligands to chelate iron(III) were evaluated in vitro at physiological pH. Chelation efficiency with iron was low and less than previously observed with aluminium(III).     

The influence of citrate, maltolate and fluoride on the gastrointestinal absorption of aluminum at a drinking water-relevant concentration: A 26Al and 14C study

The objectives were to test the null hypotheses that (1) citrate, maltolate, and fluoride do not significantly influence oral Al bioavailability, C(max) or T(max) at an Al dose relevant to drinking water exposure; and (2) Al citrate and maltolate are absorbed intact from the gastrointestinal tract. Male Fisher rats were given 1ml of solution intra-gastrically containing 1 nCi (26)Al (65nmol total Al) as the Al(3+) ion, or as complexes with (14)C-citrate, (14)C-maltolate or fluoride, during concurrent (27)Al iv infusion. Blood was repeatedly collected for serum (26)Al, total Al and (14)C quantification. Absorption parameters were estimated using WinNonlin. Al bioavailability, C(max) and T(max) from the ion, citrate, maltolate, and fluoride were 0.29+/-0.11%, 0.61+/-0.31%, 0.50+/-0.25%, and 0.35+/-0.10%; 659+/-195, 1073+/-250, 881+/-356, and 880+/-295fg/ml; and 1.2+/-0.9, 1.0+/-1.1, 1.3+/-1.0, and 1.0+/-0.9h (X+/-SD) respectively. Serum (14)C was approximately 100 times higher than (26)Al. The results suggest a non-significant enhancement of oral Al bioavailability by citrate and maltolate, some Al complex dissociation in the GI tract, and less absorption of Al than citrate or maltolate. The presence of citrate, maltolate and fluoride, at a similar molar concentration to Al, would not be expected to greatly influence Al absorption from drinking water.     

The phylogenetic origin of the bifunctional tyrosine-pathway protein in the enteric lineage of bacteria

Because bifunctional enzymes are distinctive and highly conserved products of relatively infrequent gene-fusion events, they are particularly useful markers to identify clusters of organisms at different hierarchical levels of a phylogenetic tree. Within the subdivision of gram-negative bacteria known as superfamily B, there are two distinctive types of tyrosine-pathway dehydrogenases: (1) a broad- specificity dehydrogenase (recently termed cyclohexadienyl dehydrogenase [CDH]) that can utilize either prephenate or L-arogenate as alternative substrates and (2) a bifunctional CDH that also posseses chorismate mutase activity. (T-proteins). The bifunctional T-protein, thought to be encoded by fused ancestral genes for chorismate mutase and CDH, was found to be present in enteric bacteria (Escherichia, Shigella, Salmonella, Citrobacter, Klebsiella, Erwinia, Serratia, Morganella, Cedecea, Kluyvera, Hafnia, Edwardsiella, Yersinia, and Proteus) and in Aeromonas and Alteromonas. Outside of the latter "enteric lineage," the T-protein is absent in other major superfamily-B genera, such as Pseudomonas (rRNA homology group I), Xanthomonas, Acinetobacter, and Oceanospirillum. Hence, the T-protein must have evolved after the divergence of the enteric and Oceanospirillum lineages. 3-Deoxy-D-arabino-heptulosonate 7-phosphate synthase-phe, an early-pathway isozyme sensitive to feedback inhibition by L- phenylalanine, has been found in each member of the enteric lineage examined. The absence of both the T-protein and DAHP synthase-phe elsewhere in superfamily B indicates the emergence of these character states at approximately the same evolutionary time.      

Biotinyl-l-3-(2-naphthyl)-alanine hydrazide derivatives of N-glycans: versatile solid-phase probes for carbohydrate-recognition studies

Biotinyl-oligosaccharides are a relatively new generation of saccharide probes that enable immobilization of desired oligosaccharides on streptavidin matrices for studies of carbohydrate-protein interactions. Here we describe the facile preparation of biotinyl-l-3-(2-naphthyl)- alanine hydrazide (BNAH) derivatives of oligosaccharides, containing a strong UV absorbing and fluorescent group, in which the ring of the reducing-end monosaccharide is nonreduced. We evaluate reactivities of immobilized BNAH- N -glycans with plant lectins that recognize aspects of the oligosaccharide core or outer-arms. We make some comparisons with 2-amino-6-amidobiotinyl-pyridine (BAP) derivatives obtained by reductive amination, and 6-(biotinyl)-aminocaproyl-hydrazide (BACH) derivatives which have a longer spacer-arm. N -Glycan-BNAH and-BAP derivatives have, overall, comparable reactivities with lectins which recognize N -glycan outer-arms or the trimannosyl core, but only BNAH and BACH derivatives are bound by lectins which recognize the non- reduced core. Moreover, with Pisum sativum agglutinin (PSA) which additionally requires the fucosyl- N- glycan-asparaginyl core for high affinity binding, the immobilized BNAH derivative (which is an alanine hydrazide beta-glycoside) can substitute for the natural beta- glycosylasparaginyl core, whereas the BACH derivative (aminocaproyl- hydrazide-beta-glycoside) is less effective. BNAH is a derivatization reagent of choice, therefore, for solid phase carbohydrate-binding experiments with immobilized N -glycans.      

New conformational constraints in isotopically (13C) enriched oligosaccharides

Multidimensional heteronuclear NMR studies have been applied to the resonance assignment and conformational analysis of 13C-enriched Neu5Acalpha2-3Galbeta1-4Glc. It is demonstrated that three-dimensional ROESY-HSQC experiments provide through-space distance restraints which cannot be observed with conventional homonuclear 1H techniques due to resonance overlap. In particular, connectivities demonstrating the existence of the "anti" conformation about the Galbeta1-4Glc glycosidic linkage are unambiguously observed. It is shown that 13C isotopic enrichment of the trisaccharide at a level >95% enables straightforward measurement of trans-glycosidic 1H-13C and 13C-13C coupling constants and a Karplus-type relation is derived for the latter. In total 15 conformational restraints were obtained for the trisaccharide in aqueous solution, all of which were in excellent agreement with theoretical parameters computed from a 5 ns molecular dynamics simulation of the glycan.      

Molecular phylogenetics of Stenodermatini bat genera: congruence of data from nuclear and mitochondrial DNA

Within the tribe Stenodermatini the systematics of the complex of species allied with the genus Artibeus has generated several alternative phylogenetic hypotheses. The most recent treatment recognized four genera (Artibeus, Dermanura, Enchisthenes, and Koopmania) and suggested that the most recent common ancestor of these four genera would include the common ancestor of all other currently recognized Stenodermatini genera except Sturnira. To test this hypothesis, we examined an EcoRI-defined nuclear satellite DNA repeat and 402 bp of DNA sequence variation from the mitochondrial cytochrome b gene. Phylogenetic conclusions based on Southern blot analyses, in situ hybridization, and mitochondrial DNA sequence data indicate that Enchisthenes is not closely related to Dermanura, Artibeus, or Koopmania and that Dermanura, Artibeus, and Koopmania shared a common ancestor after diverging from the remainder of the Stenodermatini. If our conclusions are correct, then justification for recognizing Dermanura and Koopmania as generically distinct from Artibeus must be based on the magnitude of difference that distinguishes each rather than on the conclusion that to place them as congeneric with Artibeus creates a paraphyletic taxon.      

Application of electron energy loss spectroscopy and electron spectroscopic imaging to aluminum determination in biological tissue

Electron energy loss spectroscopy (EELS) is a high spatial resolution electron microscopic technique with the potential to quantify elements at the subcellular level. The presence of each element is demonstrated by the electron energy loss edge at the energy characteristic of that element. The area of the edge may indicate the quantity of element present. Electron spectroscopic imaging (ESI) is a similar technique generating graphic images of elemental localization in the specimens. An ESI of an aluminum (Al)-loaded rabbit hippocampus showed Al only in pyramidal cell lysosomes, but no EELS edge could be obtained. To determine the sensitivity of EELS for Al and to be able to adjust the instrument to optimal operating conditions, standards containing 50–5000 ppm Al were produced. An Al-chloride:dicyclohexano-18-crown-6 (Al:crown) complex was synthesized. The purity of the complex was confirmed by nuclear magnetic resonance (NMR) spectroscopy and the percentage of Al in the complex was determined by electrothermal atomic absorption spectroscopy (ETAAS). The complex was introduced into a biological tissue embedding resin (Spurr medium) and appeared to be compatible with the resin at Al concentrations ≤500 ppm. EELS signals from the Al K edge could be obtained at a spatial resolution of 3.3 nm in a 30-nm thick section from 2.78×10^?21 g of Al, representing a sample concentration of 1% Al.     

<i>Trichoderma</i> spp. fostering growth on <i>Capsicum chinense</i> Jacq. seedlings and antagonistic against <i>Meloidogyne incognita</i>

Fourteen native strains of Trichoderma spp. from wildand agricultural pathosystems in the state of Yucatan, Mexico, with growth-promoting ability of Capsicum chinense Jacq. seedlings were evaluated and antagonistic effect of their filtrate against second-stage juveniles (J2) of Meloidogyne incognita. The strains Th05-02 and Th27-08 showed the best significant effects on plant hight variable increments 55.57 and 47.62%, theTh07-04 with 29.48% more root length, theTh02-01 and Th07-04 isolates increased from 48.71 to 84.61% in volume radical and 53.40% of total dry biomass. Statistical analysis (p≤0.001) of Th43 and Th43-13-14 filtrates caused 100% mortality at 24 and 48h. In the test of reversibility to 24 h after replacing the filtrates Th43-13, Th43-14, TH09-06 and TH20-07 by sterile distilled water, the J2 did not recover their viability, so they were considered as the best potential strains of Trichoderma spp. with antagonistic capacity in J2 of M.incognita.