Pollen–pistil interaction in protogyny and self-incompatibility system of Indian mustard (Brassica juncea (L.) Coss.)

The pollen morphology of two species of Drosera has been investigated by means of both light and electron microscopy. The apertures are situated proximally, a state rarely found in the pollen of Angiospermous plants. The pollen morphology of Aldrovanda, Dionea and Drosophyllum is compared.     

Ghrelin: a multifunctional hormone in non-mammalian vertebrates.

In mammals, ghrelin is a non-amidated peptide hormone, existing in both acylated and non-acylated forms, produced mainly from the X/A or ghrelin cells present in the mucosal layer of the stomach. Ghrelin is a natural ligand of the growth hormone (GH) secretagogue-receptor (GHS-R), and functions primarily as a GH-releasing hormone and an orexigen, as well as having several other biological actions. Among non-mammalian vertebrates, amino acid sequence of ghrelin has been reported in two species of cartilaginous fish, seven species of teleosts, two species of amphibians, one species of reptile and six species of birds. The structure and functions of ghrelin are highly conserved among vertebrates. This review presents a concise overview of ghrelin biology in non-mammalian vertebrates.     

Evidence that 2,3,7,8-tetrachlorodibenzo-p-dioxin induces NADPH cytochrome c (P-450) reductase in rat hepatoma cells in culture

The lack of aryl hydrocarbon (benzo[a]pyrene) hydroxylase (AHH) (EC 1.14.14.1) induction by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in a clone of rat hepatoma (HTC cl-1) cells is not caused by the lack of nuclear Ah receptor or by a deficiency in the activity of NADPH-cytochrome c (P-450) reductase. Treatment of HTC cl-1 cell line with TCDD for 18 h in culture resulted in a reproducible 500-600% increase in reductase activity without concomitant expression in AHH activity. These data suggests that TCDD induces cytochrome c reductase activity and that the lack of inducible AHH activity in rat hepatoma cells could reflect a defect in the structural gene (s) encoding for cytochrome P1-450, or an Ah receptor with a faulty DNA binding domain.     

In vitro studies on the interaction between human serum albumin and fosfomycin disodium salt,an antibiotic drug by multi-spectroscopic and molecular docking methods

The interaction between the human serum albumin (HSA) and drug, fosfomycin disodium salt (FOS) has been studied by different spectroscopic techniques. The experimental results showed a static quenching mechanism in the interaction of FOS with HSA. The number of binding sites, n and observed binding constant K _a were measured by fluorescence quenching method. The thermodynamic parameters ΔG°, ΔH° and ΔS° were calculated according to van’t Hoff equation. The calculated distance r between FOS and the protein is evaluated according to the theory of Förster energy transfer. A change in the secondary structure of the protein was evident from the circular dichroism measurements, synchronous fluorescence and three-dimensional fluorescence spectra.     

Selection of a suitable host for mass production of VA mycorrhizal inoculum

Summary This study was conducted to select a suitable host for maintenance and mass production of VA mycorrhiza since sudan grass does not grow well under Bangalore conditions. Of the eight grasses tested, guinea grass was found to be a better host since it is more susceptible to infection and also supported higher spore production by VA mycorrhizal fungus,Glomus fasciculatus.     

Non-productive DNA damage binding by DNA glycosylase-like protein Mag2 from Schizosaccharomyces pombe

Schizosaccharomyces pombe contains two paralogous proteins, Mag1 and Mag2, related to the helix-hairpin-helix (HhH) superfamily of alkylpurine DNA glycosylases from yeast and bacteria. Phylogenetic analysis of related proteins from four Schizosaccharomyces and other fungal species shows that the Mag1/Mag2 duplication is unique to the genus Schizosaccharomyces and most likely occurred in its ancestor. Mag1 excises N3- and N7-alkylguanines and 1,N⁶-ethenoadenine from DNA, whereas Mag2 has been reported to have no detectible alkylpurine base excision activity despite high sequence and active site similarity to Mag1. To understand this discrepancy we determined the crystal structure of Mag2 bound to abasic DNA and compared it to our previously determined Mag1–DNA structure. In contrast to Mag1, Mag2 does not flip the abasic moiety into the active site or stabilize the DNA strand 5′ to the lesion, suggesting that it is incapable of forming a catalytically competent protein–DNA complex. Subtle differences in Mag1 and Mag2 interactions with the DNA duplex illustrate how Mag2 can stall at damage sites without fully engaging the lesion. We tested our structural predictions by mutational analysis of base excision and found a single amino acid responsible at least in part for Mag2's lack of activity. Substitution of Mag2 Asp56, which caps the helix at the base of the DNA intercalation loop, with the corresponding serine residue in Mag1 endows Mag2 with ?A excision activity comparable to Mag1. This work provides novel insight into the chemical and physical determinants by which the HhH glycosylases engage DNA in a catalytically productive manner.     

Coordination Chemistry and Redox Processes in Siderophore-Mediated Iron Transport

In this mini-review we present an environmental iron mobility/transport scheme consisting of inter-related controls, whereby the first coordination shell of iron modulates the iron redox potential (E_1/2), and the oxidation state of iron controls the chemistry of the first coordination sphere and therefore the immediate chemical environment of the iron. Siderophores (microbially generated iron specific chelators) may be viewed as iron redox mediators. Siderophore chelation of environmental iron in a reduced (Fe(II)) oxidation state results in facile air oxidation of iron due to the negative redox potentials observed for Fe-siderophore complexes. This solubilizes the iron and locks it into a specific coordination environment, thereby preventing hydrolysis and precipitation. The high-spin Fe³⁺ → Fe⁺ electron transfer process may be viewed as a switch that controls the thermodynamic stability and kinetic lability of the first coordination shell. Reduction of iron(III)-siderophore complexes to iron(II)-siderophore complexes decreases thermodynamic stability, increases the rate of siderophore ligand exchange, and increases the ease of siderophore donor atom protonation, thus facilitating a rapid turnover of the first coordination shell. Results are presented for iron-siderophore pH and oxidation state dependent speciation studies that are relevant to environmental and microbial iron mobility and transport.