Structure-wise discrimination of adenine and guanine by proteins on the basis of their nonbonded interactions

We have analyzed the nonbonded interactions of the structurally similar moieties, adenine and guanine forming complexes with proteins. The results comprise (a) the amino acid–ligand atom preferences, (b) solvent accessibility of ligand atoms before and after complex formation with proteins, and (c) preferred amino acid residue atoms involved in the interactions. We have observed that the amino acid preferences involved in the hydrogen bonding interactions vary for adenine and guanine. The structural variation between the purine atoms is clearly reflected by their burial tendency in the solvent environment. Correlation of the mean amino acid preference values show the variation that exists between adenine and guanine preferences of all the amino acid residues. All our observations provide evidence for the discriminating nature of the proteins in recognizing adenine and guanine.     

THE STOMATA OF NELUMBO NUCIFERA: FORMATION,DISTRIBUTION AND DEGENERATION

Contrary to earlier reports, well-organized but fewer stomata develop on the lower surface of the leaves of Nelumbo nucifera Willd. during aerial growth. The stomata, however, become obliterated by the readjustment of neighboring epidermal cells. During initial stages of degeneration the guard cells show irregularly thickened walls, disintegrated nuclei, and highly vacuolated cytoplasm. Such abnormal features finally lead to the disappearance of stomata from the lower surface of leaves. The ontogeny, structure and distribution of stomata on leaves, perianth lobes, stamens, receptacles and carpels are described. The stomata are haplocheilic in development and are anomocytic (ranunculaceous) at maturity. The concept of a meristemoid and the significance of this study in taxonomy and phylogeny are discussed.     

Role of isovaleroyl lipids in channeling of sound in the porpoise melon

Physical properties (e.g. specific gravity, adiabatic compressibility and sound velocity) of lipids isolated from tissues from contiguous areas of the fatty melon of an echo-locating porpoise (Delphinus delphis) were determined to elucidate relations between lipid composition and structure, and sound transmission in the head. Lipid content varied greatly within the melon (13.6–77.6% of the tissue weight) and triacylglycerols (80–100%) were the major lipid components. This lipid class was composed of diisovaleroylglycerides (triacylglycerols containing two isovaleroyl moieties and a long-chain acyl moiety), monoisovaleroyldiacylglycerols and triacylglycerols consisting of long-chain acids. The lipid-rich (>45%) areas in the melon contained a high proportion (>45% of total triacylglycerols) of diisovaleroylglycerides. There were gradations of sound velocities within the melon; the lowest sound velocities were associated with high concentrations of diisovaleroylglycerides (<1400 m/s) and the highest with high concentrations of long-chain triacylglycerols. Assuming an average sound frequency of 75 kHz, and considering dimensions of melon (path length and width of 12–14 cm and 5 cm, respectively), a forward radiating lobe of 15–25 degrees is produced. Thus, the deposition of lipids of different acoustic properties in a three-dimensional matrix within the porpoise melon results in a lens for the projection of sound into the marine environment.     

Defensive role of Gossypium hirsutum L. anti-oxidative enzymes and phenolic acids in response to Spodoptera litura F. feeding

The responses of the cotton plant, Gossypium hirsutum L. to herbivory by Spodoptera litura F. was studied in various laboratory experiments as a measure to understand the defense strategies of certain plant metabolites. Insect feeding damage enhanced the concentration of total phenol content and proteins, whereas amount of carbohydrates and amino acids were reduced. The experiments on estimation of anti-oxidative enzymes revealed stimulation in peroxidase, catalase, and superoxide dismutase levels and reduction in polyphenol oxidase and phenylanine ammonia lyase levels, signifying their defensive role in the plant. Specific phenolic acid changes were further carried out using High Performance Liquid Chromatography (HPLC), and distinct elevations in the gallic acid, catechin, and caffeic acid levels were observed in the infested cotton plant. Feeding assays towards S. litura with these phenolic compounds revealed activated detoxifying enzymes including β-glucosidase, carboxyl esterase, and glutathione-S-transferase in the insect gut indicating the toxicity. The aim of present study is to aid in further use of these specific phenolic acids towards effective management of the cotton pest, S. litura.     

Orientational ordering and dynamics of the hydrate and exchangeable hydrogen atoms in crystalline crambin

Deuterium nuclear magnetic resonance studies of crambin crystals grown from deuterated solvent (2H2O/CH3CH2O2H or H2O/C2H3CH2OH) are reported. The extent to which the hydrate and exchangeable hydrogen atoms are dynamically disordered are then determined from the size of the residual deuterium quadrupole couplings, qcc. Rapid molecular reorientation (tau c-1 greater than 10(5) s-1) reduces the magnitude of the quadrupole coupling from its static value (216 kHz for solid water). We find that the room temperature spectrum of crambin is dominated by two features: a sharp line with very small residual quadrupolar coupling less than 3 kHz, and a broad pattern with a quadrupolar coupling in the range 185 to 195 kHz. The former is indicative of very nearly isotropically reorienting deuterons, whereas the latter is somewhat narrower than that observed for the amide deuterons of poly-gamma-benzyl-L-glutamate and thus indicative of deuterons that are almost but not completely stationary. By considering the nuclear magnetic resonance spectrum intensities along with the amino acid sequence, X-ray structure and the manner in which quadrupole couplings are reduced by dynamics, we conclude that the nuclear magnetic resonance signal from most of the water molecules of hydration are contained in the sharp line, i.e. reorient nearly isotropically in the crystalline protein. Unlike bulk water, which freezes abruptly in the manner of a phase transition, the water of hydration in crambin has a broad freezing range from 180 to 250K, as evidenced by the decreasing intensity of the sharp line that disappears at 180K. At temperatures between 150 and 200K, a typical hydrate molecule reorients at a rate comparable to the quadrupole coupling, 10(4) s-1 to 10(5) s-1, a process that occurs in hexagonal ice in the range of 240 to 270K. At 140K, the hydrate is stationary, tau c-1 less than 10(3) s-1. Studies of the protein crystallized from solvent deuterated only at the non-exchangeable methyl group of ethanol confirm that ethanol is in the lattice and show that this solvate behaves in much the same way as the hydrate. The refined X-ray structure has identified four ethanol solvate molecules. The deuterium spectrum at room temperature has a well-defined residual pattern with qcc = 2.2 kHz, i.e. a small-order parameter consistent with nearly isotropically reorienting molecules. The spectrum width broadens substantially only at temperatures below 200K and achieves the characteristic spectrum of a rotating methyl group with stationary C-C axis at 140K.(ABSTRACT TRUNCATED AT 400 WORDS)     

Inactivation of Factor VIIa by Antithrombin In Vitro,Ex Vivo and In Vivo: Role of Tissue Factor and Endothelial Cell Protein C Receptor

Recent studies have suggested that antithrombin (AT) could act as a significant physiologic regulator of FVIIa. However, in vitro studies showed that AT could inhibit FVIIa effectively only when it was bound to tissue factor (TF). Circulating blood is known to contain only traces of TF, at best. FVIIa also binds endothelial cell protein C receptor (EPCR), but the role of EPCR on FVIIa inactivation by AT is unknown. The present study was designed to investigate the role of TF and EPCR in inactivation of FVIIa by AT in vivo. Low human TF mice (low TF, ∼1% expression of the mouse TF level) and high human TF mice (HTF, ∼100% of the mouse TF level) were injected with human rFVIIa (120 µg kg⁻¹ body weight) via the tail vein. At varying time intervals following rFVIIa administration, blood was collected to measure FVIIa-AT complex and rFVIIa antigen levels in the plasma. Despite the large difference in TF expression in the mice, HTF mice generated only 40–50% more of FVIIa-AT complex as compared to low TF mice. Increasing the concentration of TF in vivo in HTF mice by LPS injection increased the levels of FVIIa-AT complexes by about 25%. No significant differences were found in FVIIa-AT levels among wild-type, EPCR-deficient, and EPCR-overexpressing mice. The levels of FVIIa-AT complex formed in vitro and ex vivo were much lower than that was found in vivo. In summary, our results suggest that traces of TF that may be present in circulating blood or extravascular TF that is transiently exposed during normal vessel damage contributes to inactivation of FVIIa by AT in circulation. However, TF’s role in AT inactivation of FVIIa appears to be minor and other factor(s) present in plasma, on blood cells or vascular endothelium may play a predominant role in this process.     

Isolation and Characterization of Arsenic-Resistant Bacteria from Contaminated Water-Bodies in West Bengal,India

Bengal Basin is known for severe arsenic contamination. In the present study, we have isolated six bacteria from the arsenic contaminated surface water of Bengal Basin. 16S rDNA sequence analysis identified them as Microbacterium oleivorans, Acinetobacter soli, Acinetobacter venetianus, Acinetobacter junii, Acinetobacter baumannii, Acinetobacter calcoaceticus. All the isolates possess arsenic accumulation potential and high molecular weight plasmid (>10 kb). PCR amplification indicated the presence of arsenic-resistance genes (arsB and aoxB) either in the genome or plasmid or in both in the isolated bacteria (except in Acinetobacter venetianus). Exposure to arsenic affected bacterial growth and induced alteration in cytoplasmic membrane integrity.     

Pathological implications of Gymnoascaceae

Summary The Gymnoascaceae have long been regarded by many as the perfect stages of certain imperfect dermatophytic fungi. In recent years increasing numbers of reports have been published in which the Gymnosacaceae have been isolated from pathological conditions and have often been regarded as at least potential pathogens. This paper reviews previous reports and presents certain new isolation data which should lead to a better understanding and appreciation of the role of these fungi in clinical investigations. Evidence supporting pathogencity of the Gymnoascaceae is suggestive but inconclusive.

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Zusammenfassung Manche Verfasser haben die Gymnoascaceae schon lange als die perfekten Formen von gewissen imperfekten Dermatophyten betrachtet. In den letzten Jahren ist eine wachsende Anzahl von Berichten veröffentlich worden bezüglich Gymnoascaceae, die vom pathologischen Material gezüchtet und mindestens als bedingt pathogen betrachtet worden sind. Dieser Bericht gibt eine Übersicht von früheren Befunden und bringt manche neuen Tatsachen von neuen Isolationen. Sie sollen zu einem besseren Verständnis und zu einer besseren Auswertung der Rolle dieser Hyphomyceten in der klinischen Untersuchung führen. Die Beweise betreffs der Pathogenität der Gymnoascaceae sind lediglich mutmasslich und nicht konklusiv.