Diversity of Rhizobia isolated from various Hedysarum species

Cultural and physiological properties, serology, plasmid profiles and infective traits were determined for 23 strains of rhizobia isolated from various Hedysarum species: H. coronarium (common name: sulla) (16), H. carnosum (1), H. alpinum (3), H. mackenzii (2) and H. pallens (1) from Portugal, Spain, Tunisia, Alaska and Israel. Strains isolated from H. alpinum, H. mackenzii and H. pallens have slow growth rates on yeast-extract mannitol medium and were unable to nodulate H. coronarium plants, whereas the latter were effectively nodulated by all sixteen fast growing strains from sulla. Regardless of the country of origin all H. coronarium strains fell into one serogroup and were not serologically related with strains of other Hedysarum species. The RAPD (random amplified polymorphic DNA) fingerprinting method which was carried out on five H. coronarium and three H. alpinum strains allowed distinction to be made among serologically related rhizobia. No particular plasmid profile pattern was observed in relation to the host or geographical origin of the strains.     

Availability of fixed NH4 + to crops

Summary Significantly lower amounts of exchaneable NH₄, soluble NO₃ and clay-fixed NH₄ forms of N were observed in the unfertilized fields with high rather than low-density cropped plots. Irrespective of planting densitites, the fixed NH₄ content in soil increased with increase in the period of crop growth. N uptake by plant and total bacterial population of rhizosphere soil were significantly higher in the plots with the high than with the low-density planting. Availability of native fixed NH₄ ⁺ to crops and biological utilization of a considerable amount of recently mineralized NH₄ ⁺ in fixed form is indicated.     

Heme activation by DNA: isoguanine pentaplexes,but not quadruplexes,bind heme and enhance its oxidative activity

Guanine-rich, single-stranded, DNAs and RNAs are able to fold to form G-quadruplexes that are held together by guanine base quartets. G-quadruplexes are known to bind ferric heme [Fe(III)-protoporphyrin IX] and to strongly activate such bound hemes toward peroxidase (1-electron oxidation) as well as oxygenase/peroxygenase (2-electron oxidation) activities. However, much remains unknown about how such activation is effected. Herein, we investigated whether G-quadruplexes were strictly required for heme activation or whether related multi-stranded DNA/RNA structures such as isoguanine (iG) quadruplexes and pentaplexes could also bind and activate heme. We found that iG-pentaplexes did indeed bind and activate heme comparably to G-quadruplexes; however, iG-quadruplexes did neither. Earlier structural and computational studies had suggested that while the geometry of backbone-unconstrained iG-quintets templated by cations such as Na⁺ or NH₄⁺ was planar, that of iG-quartets deviated from planarity. We hypothesize that the binding as well as activation of heme by DNA or RNA is strongly supported by the planarity of the nucleobase quartet or quintet that interacts directly with the heme.     

Beclin‐1–p53 interaction is crucial for cell fate determination in embryonal carcinoma cells

Emerging interest on the interrelationship between the apoptotic and autophagy pathways in the context of cancer chemotherapy is providing exciting discoveries. Complexes formed between molecules from both pathways present potential targets for chemotherapeutics design as disruption of such complexes could alter cell survival. This study demonstrates an important role of Beclin‐1 and p53 interaction in cell fate decision of human embryonal carcinoma cells. The findings provide evidence for p53 interaction with Beclin‐1 through the BH3 domain of the latter. This interaction facilitated Beclin‐1 ubiquitination through lysine 48 linkage, resulting in proteasome‐mediated degradation, consequently maintaining a certain constitutive level of Beclin‐1. Disruption of Beclin‐1–p53 interaction through shRNA‐mediated down‐regulation of p53 reduced Beclin‐1 ubiquitination suggesting requirement of p53 for the process. Reduction of ubiquitination consequently resulted in an increase in Beclin‐1 levels with cells showing high autophagic activity. Enforced overexpression of p53 in the p53 down‐regulated cells restored ubiquitination of Beclin‐1 reducing its level and lowering autophagic activity. The Beclin‐1–p53 interaction was also disrupted by exposure to cisplatin‐induced stress resulting in higher level of Beclin‐1 because of lesser ubiquitination. This higher concentration of Beclin‐1 increased autophagy and offered protection to the cells from cisplatin‐induced death. Inhibition of autophagy by either pharmacological or genetic means during cisplatin exposure increased apoptotic death in vitro as well as in xenograft tumours grown in vivo confirming the protective nature of autophagy. Therefore, Beclin‐1–p53 interaction defines one additional molecular subroutine crucial for cell fate decisions in embryonal carcinoma cells.     

Alteration of Bax/Bcl-2 ratio contributes to Terminalia belerica-induced apoptosis in human lung and breast carcinoma

The objective of the present study was to assess the in vitro anticancer activity of 70% methanolic extract of Terminalia belerica (TBME) against human lung (A549) and human breast (MCF-7) carcinoma and its possible mechanism. TBME showed significant cytotoxicity to both A549 and MCF-7 cells, whereas, no cytotoxicity was found in non-malignant WI-38 cells. Flow cytometric analysis was then performed and 100 μg/ml of TBME was selected as the effective concentration inducing apoptosis in A549 and MCF-7. At this concentration, TBME caused DNA fragmentation pattern of apoptosis. Furthermore, mechanism of apoptosis induction was demonstrated using western blotting and Bax/Bcl-2 ratio in both types of the cells was found increased, which leads to the activation of caspase cascade along with the cleavage of PARP. These results suggested that TBME is able to induce anticancer effects on both lung and breast cancer cell lines through the modulation of Bcl-2 family proteins.     

ppGpp: stringent response and survival

Adaptation to any undesirable change in the environment dictates the survivability of many microorganisms, with such changes generating a quick and suitable response, which guides the physiology of bacteria. During nutritional deprivation, bacteria show a stringent response, as characterized by the accumulation of (p)ppGpp, resulting in the repression of stable RNA species, such as rRNA and tRNA, with a concomitant change in colony morphology. However, genes involved in amino acid biosynthesis become over-expressed to help bacteria survive under such conditions. The survivability of pathogenic bacteria inside a host cell also depends upon the stringent response demonstrated. Therefore, an understanding of the physiology of stringent conditions becomes very interesting in regulation of the growth and persistence of such invading pathogens.     

Formation of a supramolecular ladder using dinuclear dicyanamide bridged Cu(II) species: Synthesis, crystal structure and magnetic property

The reaction of Cu(ClO₄)₂ · 6H₂O with bis(3-aminopropyl)methylamine and sodium dicyanamide in aqueous medium results in the formation of a dimeric dicyanamide complex of Cu(II), [Cu₂(medpt)₂(dca)₂](ClO₄)₂. The single crystal X-ray structure reveals that the dinuclear entities are extended to form a supramolecular 1D ladder by H-bonding. Each dinuclear entity is joined to the adjacent unit via the perchlorate anion. Variable temperature magnetic study was performed and the best-fit parameters are J = −1.20 ± 0.02 cm⁻¹, g = 2.08 ± 0.01 with R = 2 × 10⁻⁵. These clearly indicate the antiferromagnetic interaction between the Cu(II) center.     

A deliberate synthesis of a mononuclear trans-dimethoxide complex of ruthenium(III). X-ray crystal structure, electrochemistry and electron paramagnetic resonance

Using bis(3,5-dimethylpyrazol-1-yl)methane as the bidentate N donor ligand L, the yellow compound trans-[Ru^IIIL₂(OMe)₂]ClO₄ · CH₂Cl₂ is synthesized. It is a rare example of a mononuclear dialkoxo complex of Ru(III). It shows a quasireversible Ru(II/III) couple at −0.65 V versus NHE in acetonitrile at a Pt electrode. Its magnetic moment at room temperature corresponds to one unpaired electron. It displays a rhombic EPR spectrum in acetone at 77 K with g = 2.219, 2.062 and 1.855.     

trans-[Ru(N-N)2Cl2] species, where N-N is bis(3,5-dimethylpyrazol-1-yl)methane

Using bis(3,5-dimethylpyrazol-1-yl)methane as an N-N donor ligand, a trans-[Ru^III(N-N)₂Cl₂]⁺ core has been isolated from the direct reaction of the ligand with RuCl₃ · xH₂O and characterized structurally for the first time. The core displays a rhombic EPR spectrum and a quasireversible Ru(II/III) couple with an E_1/2 of −0.34 V versus NHE.