Browsing by Author "Bakir T."
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Publication Apparent dissociation constant of cellulose gum acid(2018-01-01) Bakir T.Gums are widely used in the paper, textile and petroleum industries. Gums, such as carboxymethyl cellulose (CMC) is synthetically derived from cellulose are used for microencapsulation of medicinal and food products. The aim of the study was to determine its ionization properties and acidic property. The dissociation behaviour of cellulose gum has been investigated by potentiometric titration. The apparent acidity constant, pKa and the intrinsic acidity constant, pK0, have been determined from potentiometric titrations of carboxymethyl cellulose [degree of substitution (DS) = 0.70-0.85] in salt-free aqueous solutions of various concentrations at 20 °C. Furthermore effect of different neutralizing agents were tested on the titration curves. It was found that the extended Henderson-Hasselbalch equation reproduced measured data well and the dissociation suppressed progressively either by decreasing CMC concentration or with increasing counterion size. The concentration dependence of pH for different values of degree of dissociation (α), was found in the following form for CMC (degree of substitution = 0.70-0.85), [pH]0α = 5.04 + 2.72 log [α/(1-α)].Scopus Apparent dissociation constant of cellulose gum acid(2018-01-01) Bakir T.Gums are widely used in the paper, textile and petroleum industries. Gums, such as carboxymethyl cellulose (CMC) is synthetically derived from cellulose are used for microencapsulation of medicinal and food products. The aim of the study was to determine its ionization properties and acidic property. The dissociation behaviour of cellulose gum has been investigated by potentiometric titration. The apparent acidity constant, pKa and the intrinsic acidity constant, pK0, have been determined from potentiometric titrations of carboxymethyl cellulose [degree of substitution (DS) = 0.70-0.85] in salt-free aqueous solutions of various concentrations at 20 °C. Furthermore effect of different neutralizing agents were tested on the titration curves. It was found that the extended Henderson-Hasselbalch equation reproduced measured data well and the dissociation suppressed progressively either by decreasing CMC concentration or with increasing counterion size. The concentration dependence of pH for different values of degree of dissociation (α), was found in the following form for CMC (degree of substitution = 0.70-0.85), [pH]0α = 5.04 + 2.72 log [α/(1-α)].Scopus Investigation of antioxidant activities of Pleurotus ostreatus stored at different temperatures(2018-06-01) Bakir T.; Karadeniz M.; Unal S.In this study, the antioxidant capacity of oyster mushroom (Pleurotus ostreatus) stored in five different temperature environments was investigated by DPPH (1,1 diphenyl-2-picryl hydrazyl) radical scavenging method. The antioxidant capacity results of oyster mushroom extracts were examined by spectroscopic measurements and expressed as percent of inhibition. The IC50 values of mushroom samples were calculated with DPPH method using calibration equations, and change in antioxidant properties was also tried to decipher by SEM images. The IC50 values of Pleurotus ostreatus for four different concentrations were also found in h+20°C > inh+4°C> inh−10°C> inh−20°C> inh−40°C, respectively. As a conclusion, the temperature factor of oyster mushroom in the range of −40°C to +20°C storage conditions is directly proportional to the change of antioxidant properties. The results have shown the importance of logistics and storage conditions in preserving the antioxidant properties of oyster mushroom and similar food samples.Scopus Voltammetric and theoretical study of the interaction of ceftriaxone with phenylalanine(2018-01-01) Sayiner H.S.; Bakir T.; Kandemirli F.The interaction between ceftriaxone and phenylalanine (PA) was investigated by cyclic voltammetry and quantum chemical study using DFT (density functional theory) method. The study was carried out in phosphate buffer solution (PBS) at pH 7.0 (which was also used as the supporting electrolyte) by directly dissolving it in twice distilled water. The voltammetric study of ceftriaxone showed well expressed redox peaks at 0.090 V on a GCE in phosphate buffer of pH 7.0 at 50 mVs-1. The cathodic peak currents were linear with different scan rates from 25 to 275 mVs-1 and the correlation coefficient was found to be 0.971 9 and 0.9592 for ceftriaxone and ceftriaxone-PA systems, respectively in the potential range of 0.8-(-0.2) V. The electron transfer rate constant (ks) was calculated for the reduction of ceftriaxone and ceftriaxone-PA interactions as 2.031 and 4.831 s-1, respectively. After the addition of PA to the ceftriaxone solution, the redox binding constant was obtained as K = 1.32×103 M-1 for ceftriaxone-PA interaction, and quantum chemical calculations were performed for ceftriaxone and ceftriaxone-PA complex by the B3LYP method.