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.     

Salinity stress responses in the plant growth promoting rhizobacteria,Azospirillum spp

In order to adapt to the fluctuations in soil salinity/osmolarity the bacteria of the genusAzospirillum accumulate compatible solutes such as glutamate, proline, glycine betaine, trehalose, etc. Proline seems to play a major role in osmoadaptation. With increase in osmotic stress the dominant osmolyte inA. brasilense shifts from glutamate to proline. Accumulation of proline inA. brasilense occurs by both uptake and synthesis. At higher osmolarityA. brasilense Sp7 accumulates high intracellular concentration of glycine betaine which is taken up via a high affinity glycine betaine transport system. A salinity stress induced, periplasmically located, glycine betaine binding protein (GBBP) of ca. 32 kDa size is involved in glycine betaine uptake inA. brasilense Sp7. Although a similar protein is also present inA. brasilense Cd it does not help in osmoprotection. It is not known ifA. brasilense Cd can also accumulate glycine betaine under salinity stress and if the GBBP-like protein plays any role in glycine betaine uptake. This strain, under salt stress, seems to have inadequate levels of ATP to support growth and glycine betaine uptake simultaneously. ExceptA. halopraeferens, all other species ofAzospirillum lack the ability to convert choline into glycine betaine. Mobilization of thebet ABT genes ofE. coli intoA. brasilense enables it to use choline for osmoprotection. Recently, aproU-like locus fromA. lipoferum showing physical homology to theproU gene region ofE. coli has been cloned. Replacement of this locus, after inactivation by the insertion of kanamycin resistance gene cassette, inA. lipoferum genome results in the recovery of mutants which fail to use glycine betaine as osmoprotectant.     

Microbial production of d-amino acids

The production of d-aminoacylase by Alcaligenes denitrificans and Alcaligenes faecalis has been studied. The enzyme was inducibly produced and N-acetyl-d-leucine and N-acetyl-d-valine were the most effective inducers. d-methionine, d-valine, d-phenylalamine and d-leucine were produced by the enzymic hydrolysis of the appropriate N-acetyl-d-amino-acids with whole cell biomass. The hydrolysis of N-acetyl-d-methionine by A. denitrificans and N-acetyl-d-valine by A. faecalis was preferential. Maximum yields of d-methionine and d-valine were 94.3 and 84.7% at a specific product formation rate of 20.10 and 19.19 μmol min⁻¹ mg⁻¹ of wet cells at 20 mM substrate concentration and 5 mg ml⁻¹ of cell density.     

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)     

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.     

Evaluation of the leaf juice of some higher plants for their toxicity against soil borne pathogens

Out of the leaf juices of eighteen plant species screened, only Eupatorium cannabinum exhibited complete toxicity against Pythium debaryanum, Fusarium oxysporum, Rhizoctonia solani and Sclerotium rolfsii. Shade drying of the leaves had no adverse effect, while oven drying produced an adverse effect on the fungitoxicity of the leaves of E. cannabinum. The crude leaf juice of E. cannabinum successfully inhibited damping-off (Fusarium oxysporum) infection of Pisum sativum seedlings.     

Role of calcium channel in postvagal potentiation of contraction as evident from the effects of Mn2+, La3+, D-600, and deoxycholate on isolated guinea pig atria-vagus nerve preparation

The role of the calcium channel in the first large contraction (postvagal potentiation, PVP) of the atria at the end of the inhibitory phase of its response (IPR) to vagal stimulation has been investigated by studying the effects of agents acting on the calcium channel (e.g., Ca2+, Mn2+, La3+, and D-600) or sarcoplasmic reticulum (SR) (e.g., deoxycholate (DOC)). IPR was potentiated by high [Ca2+]o (3-16 mM) and also by the calcium channel blockers, Mn2+ (1 microM-0.5 mM), La3+ (0.1 microM-0.5 mM), D-600 (1.0-10 microM), and DOC (1 microM-0.5 mM). PVP was also potentiated by enhanced [Ca2+]o, but the PVP ratio, which employs a correction for the simultaneous changes in the force of spontaneous contraction was inhibited. This indicated greater potentiation of contractility during spontaneous activity by Ca2+ than during PVP. Mn2+, La3+, and D-600 and even DOC in the above concentrations inhibited PVP but increased the PVP ratio. High concentrations of DOC (greater than 1 mM), which disrupt SR, strongly inhibited PVP. It is concluded that the calcium channel plays a more prominent role in spontaneous contractions than in PVP in guinea pig atria. PVP is suggested to be generated by excessive triggered release of Ca2+ from SR leading to a marked increase in [Ca2+]i. The calcium channel and the calcium trapped in the glycocalyx also play significant roles in PVP.     

Isolation of a hydroxyproline-secreting pigment-deficient mutant ofNostoc sp. by metronidazole selection

Summary A pigment-deficient mutant ofNostoc sp. was induced by N-methyl-N-nitro-N-nitrosoguanidine and selected in a medium containing metronidazole. It formed chains of heterocysts, grew more slowly than the control, and excreted hydroxyproline into the medium, imparting a pinkish-brown colour to the cultures.

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Aislamiento de un mutante do Nostoc sp. deficiente en pigmentos y secretor de hidroxiprolina en un medio selectivo con metronidazol

Resumen Un mutante pigmento-deficiente deNostoc sp. fue inducido mediante N-metil-N-nitro-N-nitrosoguanidina y seleccionado en un medio conteniendo metronidazol. La cepa mutante creció más lentamente que la control formando cadenas de heterocistos y excretando hidroxiprolina al medio lo cual confirió una coloración rosa-parduzca a los cultivos.

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Isolement par sélection avec le métronidazole d'un mutant de Nostoc sp. excrétant de l'hydroxyproline et déficient en pigment

Résumé Un mutant deNostoc sp. déficient en pigment a été induit par la N-méthyl-N-nitro-N-nitrosoguanidine et sélectionné dans un milieu contenant du métronidazole. Ce mutant forme des chaînes d'hétérocystes, pousse plus lentement que le contrôle, et excréte de l'hydroxyproline dans le milieu, conférant aux cultures une coloration brun rosâtre.

     

Phenolic acid effects on peanut growth and oil production

Plants of peanut (Arachis hypogaea L. var. PG No. 1) were given two foliar sprays of phenolic compounds (H-acid, 1, 2, 4-acid, resorcinol and RD-Brown) at 100 and 200 ppm, 35 and 50 days after sowing. In treated plants, shelling %, yield (kg/ha), number of gynophores per plant and number of pods per plant were significantly greater than in the control. Oil content of kernels also showed a significant increase with all the phenolic compounds applied. These compounds increased the linoleic acid concentration so improving nutritional quality. The number of gynophores was significantly correlated with the number of pods per plant and yield per hectare. The effect of phenolic compounds on growth and development was independent of their structural configuration.