Excited state interactions between the chiral Au 38 L 24 cluster and covalently attached porphyrin

A protected S-acetylthio porphyrin was synthesized and attached to the Au38(2-phenylethanethiolate)24 cluster in a ligand exchange reaction. Chiral high performance liquid chromatography of the functionalized cluster yielded enantiomeric pairs of clusters probably differing in the binding site of the porphyrin. As proven by circular dichroism, the chirality was maintained. Exciton coupling between the cluster and the chromophore is observed. Zinc can be incorporated into the porphyrin attached to the cluster, as evidenced by absorption and fluorescence spectroscopy, however, the reaction is slow. Quenching of the chromophore fluorescence is observed, which can be explained by energy transfer from the porphyrin to the cluster. Transient absorption spectra of Au38(2-phenylethanethiolate)24 and the functionalized cluster probe the bleach of the gold cluster due to ground state absorption and the characteristic excited state absorption signals. Zinc incorporation does not have a pronounced effect on the photophysical behaviour. Decay times are typical for the molecular behaviour of small monolayer protected gold clusters.

Classification of organisms previously reported as the SP and Stewart-Letscher groups, with descriptions of Necropsobacter gen. nov. and of Necropsobacter rosorum sp. nov. for organisms of the SP group

To allow classification of bacteria previously reported as the SP group and the Stewart-Letscher group, 35 isolates from rodents (21), rabbits (eight), a dog and humans (five) were phenotypically and genotypically characterized. Comparison of partial rpoB sequences showed that 34 of the isolates were closely related, demonstrating at least 97.4 % similarity. 16S rRNA gene sequence comparison of 20 selected isolates confirmed the monophyly of the SP group and revealed 98.5 %-100 % similarity between isolates. A blast search using the 16S rRNA gene sequences showed that the highest similarity outside the SP group was 95.5 % to an unclassified rat isolate. The single strain, P625, representing the Stewart-Letscher group showed the highest 16S rRNA gene similarity (94.9-95.5 %) to members of the SP group. recN gene sequence analysis of 11 representative strains resulted in similarities of 97-100 % among the SP group strains, which showed 80 % sequence similarity to the Stewart-Letscher group strain. Sequence similarity values based on the recN gene, indicative for whole genome similarity, showed the SP group being clearly separated from established genera, whereas the Stewart-Letscher group strain was associated with the SP group. A new genus, Necropsobacter gen. nov., with only one species, Necropsobacter rosorum sp. nov., is proposed to include all members of the SP group. The new genus can be separated from existing genera of the family Pasteurellaceae by at least three phenotypic characters. The most characteristic properties of the new genus are that haemolysis is not observed on bovine blood agar, positive reactions are observed in the porphyrin test, acid is produced from (+)-L-arabinose, (+)-D-xylose, dulcitol, (+)-D-galactose, (+)-D-mannose, maltose and melibiose, and negative reactions are observed for symbiotic growth, urease, ornithine decarboxylase and indole. Previous publications have documented that both ubiquinones and demethylmenaquinone were produced by the proposed type strain of the new genus, Michel A/76(T), and that the major polyamine of representative strains (type strain not included) of the genus is 1,3-diaminopropane, spermidine is present in moderate amounts and putrescine and spermine are detectable only in minor amounts. The major fatty acids of strain Michel A/76(T) are C(14 : 0), C(16 : 0), C(16:1)omega7c and summed feature C(14 : 0) 3-OH/iso-C(16 : 1) I. This fatty acid profile is typical for members of the family Pasteurellaceae. The G+C content of DNA of strain Michel A/76(T) was estimated to be 52.5 mol% in a previous investigation. The type strain is P709(T) ( = Michel A/76(T) = CCUG 28028(T) = CIP 110147(T) = CCM 7802(T)).

Regulation of human liver delta-aminolevulinic acid synthase by bile acids

Aminolevulinic acid synthase 1 (ALAS1) is the rate-limiting enzyme of heme synthesis in the liver and is highly regulated to adapt to the metabolic demand of the hepatocyte. In the present study, we describe human hepatic ALAS1 as a new direct target of the bile acid-activated nuclear receptor farnesoid X receptor (FXR). Experiments in primary human hepatocytes and in human liver slices showed that ALAS1 messenger RNA (mRNA) and activity is increased upon exposure to chenodeoxycholic acid (CDCA), the most potent natural FXR ligand, or the synthetic FXR-specific agonist GW4064. Moreover, overexpression of a constitutively active form of FXR further increased ALAS1 mRNA expression. In agreement with these observations, an FXR response element was identified in the 5' flanking region of human ALAS1 and characterized in reporter gene assays. A highly conserved FXR binding site (IR1) within a 175-bp fragment at -13 kilobases upstream of the transcriptional start site was able to trigger an FXR-specific increase in luciferase activity upon CDCA treatment. Site-directed mutagenesis of IR1 abolished this effect. Binding of FXR/retinoid acid X receptor heterodimers was demonstrated by mobility gel shift experiments. Conclusion: These data strongly support a role of bile acid-activated FXR in the regulation of human ALAS1 and, consequently, hepatic porphyrin and heme synthesis. These data also suggest that elevated endogenous bile acids may precipitate neuropsychiatric attacks in patients with acute hepatic porphyrias.

Time-dependent interactions of the two porphyrinic compounds chlorin e6 and mono-L-aspartyl-chlorin e6 with phospholipid vesicles probed by NMR spectroscopy

The distribution processes of chlorin e6 (CE) and monoaspartyl-chlorin e6 (MACE) between the outer and inner phospholipid monolayers of 1,2-dioleoyl-phosphatidylcholine (DOPC) vesicles were monitored by 1H NMR spectroscopy through analysis of chemical shifts and line widths of the DOPC vesicle resonances. Chlorin adsorption to the outer vesicle monolayer induced changes in the DOPC 1H NMR spectrum. Most pronounced was a split of the N-methyl choline resonance, allowing for separate analysis of inner and outer vesicle layers. Transbilayer distribution of the chlorin compounds was indicated by time-dependent characteristic spectral changes of the DOPC resonances. Kinetic parameters for the flip-flop processes, that is, half-lives and rate constants, were obtained from the experimental data points. In comparison to CE, MACE transbilayer movement was significantly reduced, with MACE remaining more or less attached to the outer membrane layer. The distribution coefficients for CE and MACE between the vesicular and aqueous phase were determined. Both CE and MACE exhibited a high affinity for the vesicular phase. For CE, a positive correlation was found between transfer rate and increasing molar ratio CE/DOPC. Enhanced membrane rigidity induced by increasing amounts of cholesterol into the model membrane was accompanied by a decrease of CE flip-flop rates across the membrane. The present study shows that the movement of porphyrins across membranes can efficiently be investigated by 1H NMR spectroscopy and that small changes in porphyrin structure can have large effects on membrane kinetics.

DNA-multiporhyrinic systems: promising objects for materials science

Porphyrin-containing materials are attractive objects for advanced light-harvesting systems [1]. Despite existence of numerous approaches to arrange porphyrines in a controlled and programmed way and therefore mimic natural photosynthetic systems, the problem of porphyrin`s arraying remains challenging [2]. Herein, we present an approach based on using DNA as a scaffold to hold porphyrines together. The whole spectroscopic investigation of the compounds containing several porphyrines and a possibility of their usage as molecular blocks for functional supramolecular architectures is discussed [3].

Incomplete Distal Renal Tubular Acidosis from a Heterozygous Mutation of the V-ATPase B1 Subunit

Congenital distal renal tubular acidosis (dRTA) from mutations of the B1 subunit of the V-ATPase is considered an autosomal recessive disease. We analyzed a dRTA kindred with a truncation-mutation of B1 (p.Phe468fsX487) previously shown to have failure of assembly into the V1 domain of the V-ATPase. All heterozygous carriers in this kindred have normal plasma bicarbonate concentrations, thus evaded the diagnosis of RTA. However, inappropriately high urine pH, hypocitraturia, and hypercalciuria are present either individually or in combination in the heterozygotes at baseline. Two of the heterozygotes studied also have inappropriate urinary acidification with acute ammonium chloride loading and impaired urine-blood pCO2 gradient during bicarbonaturia indicating presence of H+ gradient and flux defects. In normal human renal papillae, wild type B1 is located primarily on the plasma membrane but papilla from one of the heterozygote who had kidney stones had renal tissue secured from surgery showed B1 in both plasma membrane as well as a diffuse intracellular staining. Titrating increasing amounts of the mutant B1 subunit did not exhibit negative dominance over the expression, cellular distribution, or H+-pump activity of the wild type B1 in mammalian HEK293 cells and in V-ATPase-deficient S. cerevisiae. This is the first demonstration of renal acidification defects and nephrolithiasis in heterozygous carriers of mutant B1 subunit; which cannot be attributable to negative dominance. We propose that heterozygosity may lead to mild real acidification defects due to haploinsufficiency. B1 heterozygosity should be considered in patients with calcium nephrolithiasis and urinary abnormalities such as alkalinuria or hypocitraturia.

Assembling Multiporphyrin Stacks Inside the DNA Double Helix

Double stranded DNA hybrids containing up to four consecutive, face-to-face stacked porphyrins are described. Non-nucleosidic, 5,15-bisphenyl-substituted porphyrin building blocks were incorporated into complementary oligonucleotide strands. Upon hybridization multiple porphyrins are well accommodated inside the DNA scaffold without disturbing the overall B-DNA structure. The formation of double strands containing up to four free base porphyrins is enabled without compromising duplex stability. UV/vis, fluorescence, and CD spectroscopy demonstrate the formation of porphyrins H-aggregates inside the DNA double helix and provide evidence for the existence of strong excitonic coupling between interstrand stacked porphyrins. H-aggregation results in considerable fluorescence quenching. Most intense CD effects are observed in stacks containing four porphyrins. The findings demonstrate the value of DNA for the controlled formation of molecularly defined porphyrin aggregates.

Frederiksenia canicola gen. nov., sp. nov. isolated from dogs and human dog-bite wounds.

Polyphasic analysis was done on 24 strains of Bisgaard taxon 16 from five European countries and mainly isolated from dogs and human dog-bite wounds. The isolates represented a phenotypically and genetically homogenous group within the family Pasteurellaceae. Their phenotypic profile was similar to members of the genus Pasteurella. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry clearly identified taxon 16 and separated it from all other genera of Pasteurellaceae showing a characteristic peak combination. Taxon 16 can be further separated and identified by a RecN protein signature sequence detectable by a specific PCR. In all phylogenetic analyses based on 16S rRNA, rpoB, infB and recN genes, taxon 16 formed a monophyletic branch with intraspecies sequence similarity of at least 99.1, 90.8, 96.8 and 97.2 %, respectively. Taxon 16 showed closest genetic relationship with Bibersteinia trehalosi as to the 16S rRNA gene (95.9 %), the rpoB (89.8 %) and the recN (74.4 %), and with Actinobacillus lignieresii for infB (84.9 %). Predicted genome similarity values based on the recN gene sequences between taxon 16 isolates and the type strains of known genera of Pasteurellaceae were below the genus level. Major whole cell fatty acids for the strain HPA 21(T) are C14:0, C16:0, C18:0 and C16:1 ω7c/C15:0 iso 2OH. Major respiratory quinones are menaquinone-8, ubiquinone-8 and demethylmenaquinone-8. We propose to classify these organisms as a novel genus and species within the family of Pasteurellaceae named Frederiksenia canicola gen. nov., sp. nov. The type strain is HPA 21(T) (= CCUG 62410(T) = DSM 25797(T)).

A genomic perspective on a new bacterial genus and species from the Alcaligenaceae family, Basilea psittacipulmonis

BACKGROUND A novel Gram-negative, non-haemolytic, non-motile, rod-shaped bacterium was discovered in the lungs of a dead parakeet (Melopsittacus undulatus) that was kept in captivity in a petshop in Basel, Switzerland. The organism is described with a chemotaxonomic profile and the nearly complete genome sequence obtained through the assembly of short sequence reads. RESULTS Genome sequence analysis and characterization of respiratory quinones, fatty acids, polar lipids, and biochemical phenotype is presented here. Comparison of gene sequences revealed that the most similar species is Pelistega europaea, with BLAST identities of only 93% to the 16S rDNA gene, 76% identity to the rpoB gene, and a similar GC content (~43%) as the organism isolated from the parakeet, DSM 24701 (40%). The closest full genome sequences are those of Bordetella spp. and Taylorella spp. High-throughput sequencing reads from the Illumina-Solexa platform were assembled with the Edena de novo assembler to form 195 contigs comprising the ~2 Mb genome. Genome annotation with RAST, construction of phylogenetic trees with the 16S rDNA (rrs) gene sequence and the rpoB gene, and phylogenetic placement using other highly conserved marker genes with ML Tree all suggest that the bacterial species belongs to the Alcaligenaceae family. Analysis of samples from cages with healthy parakeets suggested that the newly discovered bacterial species is not widespread in parakeet living quarters. CONCLUSIONS Classification of this organism in the current taxonomy system requires the formation of a new genus and species. We designate the new genus Basilea and the new species psittacipulmonis. The type strain of Basilea psittacipulmonis is DSM 24701 (= CIP 110308 T, 16S rDNA gene sequence Genbank accession number JX412111 and GI 406042063).