Serap Doğan

Inhibition Kinetic of Ocimum basilicum L. Polyphenol Oxidase

The paper reports the inhibition model of the purified polyphenol oxidase (PPO) activity from basil (Ocimum basilicum L.) with L-cysteine, ethylenediaminetetraacetic acid (EDTA), ascorbic acid, gallic acid, D,L-dithiothreitol, tropolone, glutathione, sodium azide, benzoic acid, salicylic acid and 4-aminobenzoic acid inhibitors using 4-methylcatechol, catechol and pyrogallol as substrates. The inhibitors such as salicylic acid, benzoic acid and EDTA did not inhibit Ocimum basilicum L. PPO for all substrates used in this study. Purification was carried out by precipitation of contaminating proteins with (NH4)2O4 dialysis of the supernatant and a Sepharose 4B-L-tyrosine-p-aminobenzoic acid affinity chromatography. The enzyme-catalysed browning reaction was significantly inhibited in the presence of L-cysteine, ascorbic acid, gallic acid, D,L-dithiothreitol, tropolone, glutathione, sodium azide and 4-aminobenzoic acid inhibitors. It was found that the inhibition types were (i) competitive inhibition for L-cysteine, ascorbic acid, D,L-dithiothreitol, tropolone and sodium azide inhibitors using 4-methylcatechol as a substrate; for L-cysteine, ascorbic acid, gallic acid, tropolone and glutathione inhibitors using catechol as a substrate; and for ascorbic acid inhibitor using pyrogallol as a substrate, (ii) uncompetitive inhibition for gallic acid inhibitor using 4-methylcatechol as a substrate; for 4-aminobenzoic acid inhibitor using catechol as a substrate; for tropolone and 4-aminobenzoic acid inhibitors using pyrogallol as a substrate, (iii) noncompetitive inhibition for 4-aminobenzoic acid inhibitor using 4-methylcatechol as a substrate; for D,L-dithiothreitol and sodium azide inhibitors using catechol as a substrate; and for L-cysteine, glutathione and sodium azide inhibitors using pyrogallol as a substrate. Furthermore, tropolone was the most effective inhibitor for Ocimum basilicum L. PPO because of its low KI value. Results showed that the type of inhibition depended on the origin of the PPO studied and also on the substrate used.

Hemocompatibility, Cytotoxicity and Genotoxicity of Poly(Methylmethacrylate)/Nanohydroxyapatite Nanocomposites Synthesized by Melt Blending Method

ABSTRACT The aim of this study was to show the hemocompatibility, cytotoxicity, and genotoxicity of nanocomposites that were synthesized with different molecular weights of poly(methyl methacrylate) (PMMA) and different concentrations of nanohydroxyapatite (nHAp). Different techniques to characterize the nanocomposites were used. The cytotoxicity and genotoxic effects of the polymers and nanocomposites on human lymphocytes were determined by acid phosphatase assay, viability test, and comet assay. Moreover, hemocompatibility test was performed. It was found that all of the PMMA/nHAp nanocomposites are highly hemocompatible and biocompatible, none of the nanocomposites showed a cytotoxic effect, and nHAp addition decreased the genotoxicity. GRAPHICAL ABSTRACT

Biological properties of PMMA/nHAp and PMMA/3-APT-nHAp nanocomposites

ABSTRACT In this study, nanocomposite-implant materials with the filler materials, which are nanohydroxyapatite (nHAp) and nHAp modified by [3-(2-aminoethilamino)propyl]trimethoxysilane, using poly(methylmethacrylate) as a matrix according to the melting method, were synthesized. The nanocomposites were characterized using X-ray diffraction, Fourier transform infrared spectroscopy–attenuated total reflectance, scanning electron microscopy, transmission electron microscopy, differential thermal analysis/thermogravimetric analysis, and differential scanning calorimetry devices. Experimental results showed that the thermal stability of nanocomposites increased, and they were hemocompatible, had no negative effect on antioxidant enzymes, and had antibacterial activity. GRAPHICAL ABSTRACT

The Rheological Properties of Turkish Delight

In the food industry, rheological properties, such as viscosity, shear rate, and shear stress, are the most important parameters required in the design of a technological process. Therefore, in this study, we determined the flow behavior and the time-dependent flow properties of Turkish Delight (TD) in the temperature range of 25-75°C using a capillar rheometer. The structure and thermal properties of TD were investigated by XRD and a simultaneous DTA/TG analysis. The shear rate values ranged from 5 to 300s-1. We found that: (i) TD behaved as non- Newtonian pseudoplastic foodstuff; (ii) while the measurement temperature increased, viscosity decreased; and (iii) TD was a rheopectic material. The effect of temperature on viscosity was described by means of the Arrhenius equation. The activation energies for the flow of pseudoplastic TD varied from 50.1-74.2 kJ/mol, depending on shear rate. Three models were used to predict the flow behavior of TD, namely, the Power law, Bingham and Casson models. The Power law model adequately described well the flow behavior of TD at different temperatures.