Coordination polymers of Ln(III): Synthesis, characterization, catalytic and antimicrobial aspects

Coordination polymers of HEAP-ED with La(III), Pr(III), Nd(III), Sm(III), Gd(III), Tb(III) and Dy(III) metal ions have been synthesized and characterized by elemental analyses, electronic spectra, magnetic susceptibilities, FTIR, NMR, scanning electronic microscopy (SEM) and thermogravimetric analyses. Catalytic activity of selected coordination polymers was examined for pharmaceutical important organic synthesis. Antimicrobial activity of isolated Ln(III) coordination polymers against Escherichia coli, Bacillus subtilis, Staphylococcus aureus (bacteria) and Saccharomyces cerevisiae (yeast) were measured. It was observed from the study that the Ln(III) coordination polymers acted as an efficient and effective catalysts and antimicrobial agents.     

Zinc Deficiency and Anther Development in Maize

With the onset of male reproductive phase at 28 days, zinc waswithdrawn from fifty percent of maize (Zea mays L. cv. Ganga2) plants grown in refined sand at 0.13 mg Zn liter^–1.Plants from which zinc was withdrawn developed zinc deficiencysymptoms in young leaves after 38 days and were low in tissuezinc. Their tassel formation and pollen development was retarded.Anthers failed to develop beyond freshly liberated young pollengrain stage and vessels were formed in place of sporogenoustissue in sixty percent anthers of the younger of the two florets.Anthers from these plants showed low zinc concentration andstimulated specific activities of catalase, peroxidase, ribonucleaseand acid phosphatase. On resuming normal zinc (0.13 mg Zn liter^–1) through rootsto the plants from which it was withdrawn for 17 days, vegetativegrowth was partially renewed and short axillary buds were formedbut the development of anthers remained retarded. (Received April 11, 1986; Accepted October 15, 1986)     

A baiting technique for the isolation of bacteria producing starch-hydrolysing enzymes

By baiting litter soils with raw potatoes, species of bacilli producing thermostable amylases and raw starch-degrading amylase were selectively isolated.     

Effect of nutritional copper deficiency on carrageenin edema in the rat

The effects of nutritional copper deficiency on carrageenin edema in the rat were investigated with emphasis on studying the correlation between the degree of copper deficiency and the degree of edema. Carrageenin paw edema in both copper-sufficient and copper-deficient groups of rats was compared after either 20, 40, or 60 d on respective diets. The degree of copper deficiency was quantitated by analyzing total copper concentrations in a number of tissues. Other copper dependent parameters were also determined. Results indicated that: (1) although copper sufficient rats showed relatively little change in the degree of edema, copper-deficient rats showed a steady and significant increase in edema from d 20 to 40 to 60; (2) paw edema in copper-deficient animals was highly and negatively correlated to the concentrations of copper in the liver; the correlation with liver Cu,Zn-superoxide dismutase activity, however, was inconsistent; (3) paw edema was not correlated either to copper concentration in tissues other than liver or to plasma ceruloplasmin activity; and (4) aggravation of carrageenin edema in copper-deficient animals seemed to be mediated via an as yet unknown secondary effect of copper deficiency.     

Import of a precursor protein into chloroplasts is inhibited by the herbicide glyphosate

Import of the precursor to 5-enolpyruvylshikimate-3-phosphate synthase (pEPSPS) into chloroplasts is inhibited by the herbicide glyphosate. Inhibition of import is maximal at glyphosate concentrations of ≥10 μm and occurs only when pEPSPS is present as a ternary complex of enzyme–shikimate-3-phosphate–glyphosate. Glyphosate alone had no effect on the import of pEPSPS since it is not known to interact with the enzyme in the absence of shikimate-3-phosphate. Experiments with wild-type and glyphosate-resistant mutant forms of pEPSPS show that inhibition of import is directly proportional to the binding constants for glyphosate. Inhibition of import is thus a direct consequence of glyphosate binding to the enzyme–shikimate-3-phosphate complex. The potential for non-specific effects of glyphosate on the chloroplast transport mechanism has been discounted by showing that import of another chloroplast-designated protein was unaffected by high concentrations of glyphosate and shikimate-3-phosphate. The mechanism of import inhibition by glyphosate is consistent with a precursor unfolding/refolding model.     

Metabolism of glyphosate in Pseudomonas sp. strain LBr

Metabolism of glyphosate (N-phosphonomethylglycine) by Pseudomonas sp. strain LBr, a bacterium isolated from a glyphosate process waste stream, was examined by a combination of solid-state 13C nuclear magnetic resonance experiments and analysis of the phosphonate composition of the growth medium. Pseudomonas sp. strain LBr was capable of eliminating 20 mM glyphosate from the growth medium, an amount approximately 20-fold greater than that reported for any other microorganism to date. The bacterium degraded high levels of glyphosate, primarily by converting it to aminomethylphosphonate, followed by release into the growth medium. Only a small amount of aminomethylphosphonate (about 0.5 to 0.7 mM), which is needed to supply phosphorus for growth, could be metabolized by the microorganism. Solid-state 13C nuclear magnetic resonance analysis of strain LBr grown on 1 mM [2-13C,15N]glyphosate showed that about 5% of the glyphosate was degraded by a separate pathway involving breakdown of glyphosate to glycine, a pathway first observed in Pseudomonas sp. strain PG2982. Thus, Pseudomonas sp. strain LBr appears to possess two distinct routes for glyphosate detoxification.     

5-Enolpyruvyl shikimate 3-phosphate synthase from Escherichia coli. Identification of Lys-22 as a potential active site residue

5-Enolpyruvyl shikimate 3-phosphate synthase catalyzes the reversible condensation of phosphoenolpyruvate and shikimate 3-phosphate to yield 5-enolpyruvyl shikimate 3-phosphate and inorganic phosphate. The enzyme is a target for the nonselective herbicide glyphosate (N-phosphonomethylglycine). In order to determine the role of lysine residues in the mechanism of action of this enzyme as well as in its inhibition by glyphosate, chemical modification studies with pyridoxal 5'-phosphate were undertaken. Incubation of the enzyme with the reagent in the absence of light resulted in a time-dependent loss of enzyme activity. The inactivation followed pseudo first-order and saturation kinetics with Kinact of 45 microM and a maximum rate constant of 1.1 min-1. The inactivation rate increased with increase in pH, with a titratable pK of 7.6. Activity of the inactive enzyme was restored by addition of amino thiol compounds. Reaction of enzyme with pyridoxal 5'-phosphate was prevented in the presence of substrates or substrate plus glyphosate, an inhibitor of the enzyme. Upon 90% inactivation, approximately 1 mol of pyridoxal 5'-phosphate was incorporated per mol of enzyme. The azomethine linkage between pyridoxal 5'-phosphate and the enzyme was reduced by NaB3H4. Tryptic digestion followed by reverse phase chromatographic separation resulted in the isolation of a peptide which contained the pyridoxal 5'-phosphate moiety as well as 3H label. By amino acid sequencing of this peptide, the modified residue was identified as Lys-22. The amino acid sequence around Lys-22 is conserved in bacterial, fungal, as well as plant enzymes suggesting that this region may constitute a part of the enzyme's active site.