Effect of inorganic salts on free radicals production by near UV irradiation of frozen aqueous solutions of adenine and its derivatives

The addition of Na and Ca chlorides to adenine (A), adenosine (Ado) and adenosine diphosphate solutions at pH 5.3 has been shown to result in intensification of EPR signals in samples irradiated by near UV at 77 K and appearance of signals of Cl ₂ ^?? and peroxyl radicals. The peroxyl radicals contribution can exceed 30% of total amount of paramagnetic products. The addition of inorganic phosphate reduces the contribution of peroxyl radicals. Possible mechanisms of the processes involved are discussed.     

Free radicals photosensitized by near-UV radiation in aqueous adenine solutions in the presence of inorganic phosphate at 77 K

It was shown that irradiation of aqueous adenine solutions in the presence of inorganic phosphate by near UV at 77 K results in the production of OH* free radicals catalyzed by phosphate and photosensitized formation of phosphate radicals and atoms H*.     

Influence of inorganic phosphate and organic buffers on cephalosporin production by Streptomyces clavuligerus

A high concentration of potassium phosphate (75–100 mM) stabilized pH and supported extensive growth of Streptomyces clavuligerus in a chemically defined medium; such a concentration also inhibited cephalosporin production. Although Tris buffer was found to have detrimental effects on growth and antibiotic production, 3-(N-morpholino)-propane sulfonate (MOPS) or 2-(N-morpholino)-ethane sulfonate (MES) buffer provided a nontoxic buffering system. In the presence of MOPS buffer, cephalosporin production was optimal at 25 mM phosphate, whereas higher concentrations of phosphate progressively inhibited antibiotic production up to 85% without modifying the pH pattern. MOPS buffer can be used to conduct fermentations at a relatively constant pH value in shake flasks.List of Non-Common Abbreviations MOPS 3-(N-morpholino)propane sulfonic acid - MES 2-(N-morpholino)ethane sulfonic acid     

Synthesis of ATP and free radicals in an aqueous solution, containing NADH, riboflavin, ADP and inorganic phosphate

pH-dependence of initial (admixture) adenosine triphosphate (ATP) changes (ATP synthesis and hydrolysis) was studied for aerated and deaerated aqueous solutions during the incubation of adenosine diphosphate (ADP) and inorganic phosphate (Pi) in the presence of reduced nicotinamide adenine dinucleotide (NADH) and riboflavin (Rf). The preferential pH regions were indicated both for ATP synthesis and ATP hydrolysis (pH less than pH 5.4, 5.9 divided by pH 6.5 and pH greater than 6.6, pH 5.5 divided by pH 5.8 respectively). 'Free radical content measurements were paralleled by ESR technique. On the basis of the obtained results it was assumed that a part of ESP signal attributed to ADP radicals was increased during ATP synthesis.     

Influence of inorganic phosphate and immobilization on Claviceps purpurea

Summary The influence of inorganic phosphate and immobilization on cells of Claviceps purpurea strain 1029/N5 producing ergot peptides in shake culture was examined. Immobilization in Ca-alginate beads resulted in a marked reduction of some metabolic activities, i.e. the periods of alkaloid formation and cell growth were prolonged. High concentrations of inorganic phosphate (1 g/l KH₂PO₄) could reduce or stop alkaloid formation both by free and immobilized cells at any time during fermentation. The optimum phosphate concentration for alkaloid production by immobilized cells (about 0.5 mM) was a quarter of that required by free cells. This optimum shift was attributed to (i) the diminished phosphate demand of immobilized cells, due to their reduced metabolic activities, and (ii) the phosphate-dependent morphological behaviour of the biocatalyst. The observed decrease in alkaloid concentrations during later periods of the fermentation supported the idea of alkaloid-degradative enzymes, activated by high phosphate concentrations. Immobilization showed an advantageous influence on this undesirable effect. Offprint requests to: H.J. Rehm     

Analysis of free-radical products of near-UV irradiation at 77 K of frozen adenine and adenosine diphosphate solutions containing inorganic phosphate

Irradiation by near-UV light at 77 K of aqueous solutions of inorganic phosphate in weakly acidic conditions in the presence of the photosensitizers adenine and adenosine diphosphate results in the formation of free radicals of these compounds, photosensitized free radicals of phosphate itself, and H* and OH* radicals. The relative concentrations of free radical products were estimated by the analysis of total ESR signals registered in the region of g = 2.00 in the photosystems Ade + Pi and Adphi + Pi using the original computer program of ESR spectra simulation.     

The effect of inorganic phosphate on the ethylene production in tomato and apple fruits

Tomato fruits on stems immersed in phosphate solution 0.2 M K₂HPO₄ produced less ethylene than control fruits on stems immersed in water. Phosphate mediated inhibition of ethylene production was found to be the highest in fruits in the pink stage of maturity, which produced ethylene at the highest rate. Phosphate also inhibited ethylene production in slices prepared from maturing fruits, both apple and tomato. We suggest that phosphate is an inhibitor of ethylene biosynthesis in sufficiently mature tomato and apple fruits in which the rise of ethylene production is already very rapid. Presented at the International Symposium “Plant Growth Regulators” held on June 18–22, 1984 at Liblice, Czechoslovakia.