Efficient oxidative modification of polysaccharides in water using H2O2 activated by iron sulfophthalocyanine

Selective and environmentally friendly oxidation of polysaccharides by hydrogen peroxide in the presence of iron tetrasulfophthalocyanine (FePcS) catalyst was studied in aqueous media. Oxidation under mild conditions led to the cleavage of the C–C bond of vicinal diols of glycoside units as a result of carbonyl and carboxyl formation. Optimized experimental conditions allowed oxidation of hydroxyethylcellulose (HEC), sodium carboxymethylcellulose (NaCMC), guar gum (GG), and inulin to the extent of 19, 30, 53, 23 carbonyl functions per 100 anhydroglucose units, respectively. Possible explanation for this relatively modest conversion is discussed. Over-oxidation phenomena appear to play an important role during the oxidation process.     

Synthesis and splice-redirecting activity of branched, arginine-rich peptide dendrimer conjugates of peptide nucleic acid oligonucleotides

Arginine-rich cell-penetrating peptides have found excellent utility in cell and in vivo models for enhancement of delivery of attached charge-neutral PNA or PMO oligonucleotides. We report the synthesis of dendrimeric peptides containing 2- or 4-branched arms each having one or more R-Ahx-R motifs and their disulfide conjugation to a PNA705 splice-redirecting oligonucleotide. Conjugates were assayed in a HeLa pLuc705 cell assay for luciferase up-regulation and splicing redirection. Whereas 8-Arg branched peptide-PNA conjugates showed poor activity compared to a linear (R-Ahx-R)(4)-PNA conjugate, 2-branched and some 4-branched 12 and 16 Arg peptide-PNA conjugates showed activity similar to that of the corresponding linear peptide-PNA conjugates. Many of the 12- and 16-Arg conjugates retained significant activity in the presence of serum. Evidence showed that biological activity in HeLa pLuc705 cells of the PNA conjugates of branched and linear (R-Ahx-R) peptides is associated with an energy-dependent uptake pathway, predominantly clathrin-dependent, but also with some caveolae dependence.     

Replication Timing of Human Telomeres Is Chromosome Arm–Specific,Influenced by Subtelomeric Structures and Connected to Nuclear Localization

The mechanisms governing telomere replication in humans are still poorly understood. To fill this gap, we investigated the timing of replication of single telomeres in human cells. Using in situ hybridization techniques, we have found that specific telomeres have preferential time windows for replication during the S-phase and that these intervals do not depend upon telomere length and are largely conserved between homologous chromosomes and between individuals, even in the presence of large subtelomeric segmental polymorphisms. Importantly, we show that one copy of the 3.3 kb macrosatellite repeat D4Z4, present in the subtelomeric region of the late replicating 4q35 telomere, is sufficient to confer both a more peripheral localization and a later-replicating property to a de novo formed telomere. Also, the presence of β-satellite repeats next to a newly created telomere is sufficient to delay its replication timing. Remarkably, several native, non-D4Z4–associated, late-replicating telomeres show a preferential localization toward the nuclear periphery, while several early-replicating telomeres are associated with the inner nuclear volume. We propose that, in humans, chromosome arm–specific subtelomeric sequences may influence both the spatial distribution of telomeres in the nucleus and their replication timing.     

One step selective 5'-O-allylation of thymidine using microwave or ultrasound activation

An improved procedures for the synthesis of 5'-O-allylthymidine via one step selective allylation of thymidine using either ultrasound or microwave activation is described.     

Mutagenic and membranal effect of a phytotoxic molecule isolated from olive leaves parasitized by the fungusCycloconium oleaginum Cast

A phytotoxic substance (C₂₃H₄₄O₃) which is named Substance A, was purified from olive leaves infected withCycloconium oleaginum Cast. The mutagenic effect of this substance was detected using TA 100 and TA 102 strains ofSalmonella in the Ames test usingBacillus subtilis strains M45 rec^–, H17 rec⁺ in the rec assay. Another substance manifesting the mutagenic effect was found in the extract from theCycloconium oleaginum culture. This substance was not detected in the extract from contaminated olive leaves. Substance A increased electrolytes leakage from tissue of olive leaves, thus manifesting its phytotoxicity.     

Long-term effects of crop management on Rhizobium leguminosarum biovar viciae populations

Little is known about factors that affect the indigenous populations of rhizobia in soils. We compared the abundance, diversity and genetic structure of Rhizobium leguminosarum biovar viciae populations in soils under different crop managements, i.e., wheat and maize monocultures, crop rotation, and permanent grassland. Rhizobial populations were sampled from nodules of pea- or vetch plants grown in soils collected at three geographically distant sites in France, each site comprising a plot under long-term maize monoculture. Molecular characterization of isolates was performed by PCR-restriction fragment length polymorphism of 16S-23S rDNA intergenic spacer as a neutral marker of the genomic background, and PCR-restriction fragment length 0polymorphism of a nodulation gene region, nodD, as a marker of the symbiotic function. The diversity, estimated by richness in types and Simpson's index, was consistently and remarkably lower in soils under maize monoculture than under the other soil managements at the three sites, except for the permanent grassland. The highest level of diversity was found under wheat monoculture. Nucleotide sequences of the main rDNA intergenic spacer types were determined and sequence analysis showed that the prevalent genotypes in the three maize fields were closely related. These results suggest that long-term maize monoculturing decreased the diversity of R. leguminosarum biovar viciae populations and favored a specific subgroup of genotypes, but the size of these populations was generally preserved. We also observed a shift in the distribution of the symbiotic genotypes within the populations under maize monoculture, but the diversity of the symbiotic genotypes was less affected than that of IGS types. The possible effect of such changes on biological nitrogen fixation remains unknown and this requires further investigation.     

The expression of the NADPH oxidase subunit p22phox is regulated by a redox-sensitive pathway in endothelial cells

Endothelial dysfunction is characterized by increased levels of reactive oxygen species (ROS) and a prothrombotic state. The mechanisms linking thrombosis to ROS production in the endothelium are not well understood. We investigated the role of thrombin in regulating NADPH oxidase-dependent ROS production and expression of its subunit p22phox in the endothelial cell line EaHy926. Thrombin elicited a biphasic increase in ROS generation peaking within 15 min, but also at 3 h. The delayed response was accompanied by increased p22phox mRNA and protein expression. Two-photon confocal laser microscopy showed colocalization between p22phox and ROS production. Antioxidant treatment with vitamin C or diphenyleneiodonium abrogated thrombin-induced ROS production and p22phox expression, whereas H2O2 elevated ROS production and p22phox levels. Both responses were dependent on p38 MAP kinase and phosphatidylinositol-3-kinase (PI3 kinase)/Akt. Finally, p22phox was required for thrombin- or H2O2-stimulated proliferation. These data show that thrombin rapidly increases ROS production in endothelial cells, resulting, via activation of p38 MAP kinase and PI3 kinase/Akt, in upregulation of p22phox accompanied by a delayed increase in ROS generation and enhanced proliferation. These findings suggest a positive feedback mechanism whereby ROS, possibly generated by the NADPH oxidase, lead to elevated levels of p22phox and, thus, sustained ROS generation as is observed in endothelial dysfunction.     

New dinucleoside analogues via cross-coupling metathesis

Synthesis of 3'-3', 5-5', and 3'-5' dimeric thymidine, linked by an olefinic chain between glycosidic moieties is described. Cross metathesis reaction of 3' or 5' O-allyl analogues of thymidine led to the expected 3'-3' and 5'-5' dimeric compounds, respectively. In order to obtain the 3'-5' dimer, 5'-O-allyl and 3'-O-allyl monomers were first linked by their free 3' OH and 5' OH groups through a glutaryl spacer; ring closing metathesis was then operated upon this temporary dimer, followed by glutaryl removal.     

Effects of marginal iron overload on iron homeostasis and immune function in alveolar macrophages isolated from pregnant and normal rats

The effects of changes in macrophage iron status, induced by single or multiple iron injections, iron depletion or pregnancy, on both immune function and mRNA expression of genes involved in iron influx and egress have been evaluated. Macrophages isolated from iron deficient rats, or pregnant rats at day 21 of gestation, either supplemented with a single dose of iron dextran, 10 mg, at the commencement of pregnancy, or not, showed significant increases of macrophage ferroportin mRNA expression, which was paralleled by significant decreases in hepatic Hamp mRNA expression. IRP activity in macrophages was not significantly altered by iron status or the inducement of pregnancy ± a single iron supplement. Macrophage immune function was significantly altered by iron supplementation and pregnancy. Iron supplementation, alone or combined with pregnancy, increased the activities of both NADPH oxidase and nuclear factor kappa B (NFκB). In contrast, the imposition of pregnancy reduced the ability of these parameters to respond to an inflammatory stimuli. Increasing iron status, if only marginally, will reduce the ability of macrophages to mount a sustained response to inflammation as well as altering iron homeostatic mechanisms.