The effect of medium acidity on the light-dependent antibacterial activity of fatty acids

The goal of this work was to study how the acidity of a medium influenced the light-dependent antibacterial activity of fatty acids towards Staphylococcus aureus. The antibacterial activity of arachidonic, linolenic, linoleic and oleic acids increased abruptly (by 1-2 orders of magnitude) under the action of visible light, it became more intensive with a rise in the number of double bonds in a fatty acid molecule, and the maximum shifted from the neutral region to an alkaline one as the aeration was intensified. In the case of saturated fatty acids (palmitic and stearic), the antibacterial activity with a maximum in the alkaline region was detected only in the light. The effect exerted by the number of double bonds in a fatty acid molecule and by the acidity of a medium on the mechanisms of fatty acid photooxidation is discussed.     

Dependence of erythromycin biosynthesis on the active acidity of the medium]

Dependence of erythromycin biosynthesis on the medium active acidity was studied by the following methods: by changing pH of the initial medium, by changing the concentration of the medium components determining the active acidity of the culture, by using buffer mixtures by automatic control of pH. It was found that pH of the initial medium within 5.7-8.1 had no effect on the culture growth. Biosynthesis of erythromycin markedly decreased at pH 6.3 or lower. The values of pH within 6.6-7.5 (optimal values 6.7-6.9) were favourable for the antibiotic biosynthesis. At pH 6.2-6.3 the antibiotic accumulation was equal to 5-10 per cent of the control.     

The effect of temperature on antibacterial activity of biosynthesized silver nanoparticles

The purpose of this study was the evaluation of two different temperatures on antibacterial activity of the biosynthesized silver nanoparticles. 38 silver nanoparticles-producing bacteria were isolated from soil and identified. Biosynthesis of silver nanoparticles by these bacteria was verified through visible light spectrophotometry. Two strains were relatively active for production of silver nanoparticles. These strains were subjected for molecular identification and recognized as Bacillus sp. and Acinetobacter schindleri. In the present study, the effect of temperatures was evaluated on structure and antimicrobial properties of the silver nanoparrticles by transmission electron microscopy (TEM), X-ray diffraction (XRD) analysis and antimicrobial Agar well diffusion methods. The silver nanoparticles showed antibacterial activity against all the pathogenic bacteria; however, this property was lost after treatment of the silver nanoparticles by high temperatures (100 and 300 °C). TEM images showed that the average sizes of heated silver nanoparticles were >100 nm. However, these were <100 nm for non-heated silver nanoparticles. Although, XRD patterns showed the crystalline structure of heated silver nanoparticles, their antibacterial activities were less. This was possible because of the sizes and accordingly less penetration of the particles into the bacterial cells. In addition, elimination of the capping agents by heat might be considered another reason.     

The light-dependent effect of external pH on the membrane potential of Nitella

In the light the membrane potential of Nitella flexilis andNitella axilliformis was hyperpolarized by raising the externalpH above pH 5.5, at the rate of 30–40 mV/pH below pH 8.This hyperpolarization was largely reduced in the dark. The membrane potential was sensitive to the external pH of mediawith a low potassium concentration, where it was relativelyinsensitive to potassium concentration. In media of a high concentrationwhere it was sensitive to the potassium concentration, the membranebecame insensitive to the external pH. The transition from apH-sensitive to a pH-insensitive state occurred rather abruptlyon increasing the external potassium concentration. (Received September 1, 1972; )     

The effect of serotonin on the functional activity of monocytes]

The treatment of human peripheral blood monocytes with serotonin at concentrations 10(-3) and 10(-5) M over 20 minutes decreases a zymosan-induced luminol-dependent chemiluminescence of cells, whereas a 5 minutes treatment with serotonin at the concentration of 10(-5) M increases the chemoluminescence. The correlated change in monocyte capacity of secreting hydrogen peroxide has been registered. Serotonin activates, to a little extent, the monocyte capacity of phagocytizing the opsonised sheep erythrocyte. The maximum increase (2-3 times) of intracellular cAMP content and the decrease in cytosol cAMP-binding capacity are registered after a 5 minutes incubation. The lowering of the share of irreversibly bound in vitro cAMP under the influence of serotonin may suggest a preferable binding of cyclic nucleotide in vivo by regulatory subunits of cAMP-dependent protein kinase I.     

The effect of the acidity of rapeseed oil on its transesterification

The aim of this work is to study the transesterification of vegetable oil with a high acid number at unchanged reaction conditions. Rapeseed oil was used as the raw material and its acid number was changed by the addition of oleic acid (from 0.89 to 12.25 mg KOH/g). Methanol was used for transesterification (molar ratio of oil to methanol 1:6) and potassium hydroxide was used as a catalyst. After the reaction time, the residue of the catalyst was neutralised by gaseous carbon dioxide and the methanol excess was removed. After the separation of two phases, each of them was analyzed (in the ester phase: yield, content of methyl ester and acid number; in the glycerol phase: yield, density, viscosity, content of glycerol, soaps, methyl ester, potassium carbonate and hydrogen carbonate). The obtained data was compared with theoretical material balances and the effect on the saponification of oil was discussed. The results show that the yield of methyl ester (biodiesel) is significantly affected by a higher acid number, as well as enhanced soap formation. On the other hand, the conversion of the oil and acid number of the ester phase remain at constant values in studied borders.     

抗菌肽CM4对串珠镰孢菌孢子的抑制杀伤效应

The antibacterial peptide CM4 inhibits growth of conidia of Fusaricum moniliforme. The observation by using the electron microscope showed that some cells were empty and interior structure twisted into helix. Conidia cells in control group were in good condition, normally grew up. The fungal conidia treated with the antibacterial peptide CM4, then confocal laser scanning microscope were performed. As a result, it was showed that FITC-labeled peptide assembled in cells, centre of which had more peptides than two ends. Then conidia split, became empty. Finally the cells plasma membrane disintegrated and died, lead to small fragments.     

The effect of remote chirality on the antibacterial activity of indolinyl, tetrahydroquinolyl and dihydrobenzoxazinyl oxazolidinones

The oxazolidinones are promising agents for the treatment of infections caused by gram-positive bacteria, including multidrug-resistant strains. In ongoing studies we have discovered that a strategically placed chiral center of appropriate absolute configuration improves the antibacterial activity of indolinyl oxazolidinone analogues (gram-positive MIC's<0.5 microg/mL for the most potent congeners). The design, synthesis, antibacterial activity and pharmacokinetic profile of a selected series of alpha-methylated indoline derivatives and a related set of tetrahydroquinolyl and dihydrobenzoxazinyl analogues are discussed.     

The effect of 1-adamantyl radicals on curare-like activity]

In the series of polymethylene bis-ammonium salts R(CH3)2N(CH2)NN(CH3)2R . 2I--(R=CH3 or Ad) a study was made of the significance of hydrophobic 1-adamantyle radicals (1--Ad) for curare-like activity. Administration of 1-ad radicals into the cation groups of depolarizing agents (n-9--11) altered their mechanism of action and diminished their activity. Attachmeni of 1-Ad radicals to the both quarternary nitrogen atoms of the antidepolarizing agents (n=5 and 6) sharply increased their curare-like activity. The data obtained pointed to the presence of hydrophobic zones in the cholinoreceptors of skeletal muscles.