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    Antimicrobial activity of the tar obtained from the roots and stems of Pinus brutia
    (Taylor & Francis Ltd, 2002) Kizil, M; Kizil, G; Yavuz, M; Aytekin, Ç
    The antimicrobial activity of the crude and methanol, hexane, chloroform. petroleum ether, ethyl acetate and n-butanol extracts of tar obtained from the roots and stems of Pinus brutia Ten., used in the folk medicine of Turkey, were screened in vitro for antimicrobial activity against clinically isolated bacterial strains: Staphylococcus aureus ( 15 isolates), Streptococcus pyogenes ( 12 isolates), Escherichia coli (17 isolates) and the yeast fungus Candida albicans (3 isolates) by the paper disc diffusion method. Results revealed that a crude extract of the tar is highly effective against all tested microorganisms by preventing their growth to a significant extent. All the organic extracts showed similar moderate antimicrobial activity against tested microorganisms at a concentration of 80 mug/mL. The results demonstrate that the crude tar extract has a very broad spectrum of activity, and suggests that it may be useful in the treatment of various microbial infections, The results suggest that traditional folk medicine could be used a guide in our continuing search for new natural products with potential medicinal properties.
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    DNA cleavage activity of diazonium salts
    (Scientific Technical Research Council Turkey, 2003) Kizil, M; Yilmaz, EI; Pirinççioglu, N; Aytekin, Ç
    4-Fenoldiazonium tetrafluoroborate and 4-benzoicaciddiazonium tetrafluoroborate was prepared and was shown to be an effective DNA cleavage agent in the presence of the 1-electron donor copper(II) chloride. Its mechanism involves the generation of the aryl radical cleaving DNA by hydrogen atom abstraction from deoxyribose sugar.
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    Effect of proteolytic treatment on dyeing of casein with synthetic dyes
    (Asian Journal Of Chemistry, 2006) Dogru, M; Baysal, Z; Aytekin, Ç
    The activity of proteolytic enzymes is commonly measured using casein as a substrate. Modified caseinolysis assay was developed with synthetic dyes such as procion red, procion yellow and procion blue for subtilisin carlsberg, protease type XVI, trypsin, chymotrypsin, respectively. Optimum pH, incubation time were determined. K-M, V-max and k(cat)/K-M values were also determined for these enzymes. The results indicate that the effect of all the tested enzymes on the synthetic dye-casein complexes; the most appropriate complex was found to be procion yellow.
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    Production of a-amylase by thermotolerant Bacillus subtilis in the presence of some carbon, nitrogen containing compounds and surfactants
    (Inst Microbiologia, 2003) Baysal, Z; Uyar, F; Aytekin, Ç
    The effect of some carbon, nitrogen sources and surfactants on the alpha-amylase production of Bacillus subtilis isolated from hot-spring water was investigated. Galactose, glucose, xylose, sucrose. fructose or corn starch were used as a carbon sources for production of alpha-amylase. Methionine, glycine, aspartic acid, lysine, (NH4)(2)SO4, NH4Cl, (NH4)(2)S2O8 and NH4NO3 were used as a organic and inorganic nitrogen sources, respectively. The higher alpha-amylase production was determined in corn starch, Sucrose, fructose and galactose compared to other sugars and with lysine and methionine than compared with other organic nitrogen sources. Nitrate and aspartic acid are clearly not as good a nitrogen Source for alpha-amylase production. When Triton X 100, sodium dodecyl Sulphate (SDS) and Tween 40 were employed in growth medium, although bacterial growth was found high, enzyme production was not detectable. Soluble starch and yeast extract were used in order to evaluate the influence of the medium composition on the alpha-amylase production instead of sole carbon and nitrogen Sources. Maximum enzyme production was found in 3.5 % and 1.5% soluble starch and yeast extract growth media, respectively.
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    Suitability of animals' purified milk caseins and their subunit ?-caseins as substrates for subtilisin and trypsin
    (Marcel Dekker Inc, 2001) Dogru, M; Baysal, Z; Aytekin, Ç
    Acid casein and K-casein were purified from different species of animal's milk, such as cow, sheep, goat, and water buffalo. These caseins were used as substrates for commercially available subtilisin and trypsin. It was established that, when acid caseins were used as a substrate for subtilisin, cow acid casein was found to be a better substrate for the enzymes, compared to other animals' milk casein. It was suggested that this acid casein has significantly more aromatic amino acids, as compared to arginine and lysine. K-m and V-max values, which were obtained for cow K-casein, showed that cow K-casein was a better susbstrate for trypsin than the others, suggesting that cow Ic-casein has a rich content of lysine, arginine, and aromatic amino acids by comparison with the others. The calculated C/N ratio also supports this suggestion.
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    Use of natural dye-casein complexes
    (Taylor & Francis Inc, 2006) Dogru, M; Baysal, Z; Aytekin, Ç; Aydin, H
    The activity of proteolytic enzymes is commonly measured using casein as a substrate. A modified caseinolysis assay was developed with natural dyes such as juglone, lawsone, berberine, and quercetin for Subtilisin carlsberg , protease type XVI, and trypsin, respectively. The pH dependence and incubation time were determined. K-m, V-max, and k(cat)/K-m values were also determined for these enzymes. Lawsone was found to be a better substrate than the others.