Nalan Özdemir

Speciation analysis of inorganic Sb(III) and Sb(V) ions by using mini column filled with Amberlite XAD-8 resin

The speciation of inorganic Sb(III) and Sb(V) ions in aqueous solution was studied. The adsorption behavior of Sb(III) and Sb(V) ions were investigated as iodo and ammonium pyrollidine dithiocarbamate (APDC) complexes on a column filled with Amberlite XAD-8 resin. Sb(III) and Sb(V) ions were recovered quantitatively and simultaneously from a solution containing 0.8M NaI and 0.2M H 2 SO 4 by the XAD-8 column. Sb(III) ions were also adsorbed quantitatively as an APDC complex, but the recovery of the Sb(V)-APDC complex was found to be <10% at pH 5. According to these data, the concentrations of total antimony as Sb(III) + Sb(V) ions and Sb(III) ion were determined with XAD-8/NaI + H 2 SO 4 and XAD-8/APDC systems, respectively. The Sb(V) ion concentration was calculated by subtracting the Sb(III) concentration found with XAD-8/APDC system from the total antimony concentration found with XAD-8/NaI + H 2 SO 4 system. The developed method was applied to determine Sb(III) and Sb(V) ions in samples of artificial seawater and wastewater.

Preparation of lactoperoxidase incorporated hybrid nanoflower and its excellent activity and stability.

We report a green approach to synthesize lactoperoxidase (LPO) enzyme and metal ions hybrid nanoflowers (HNFs) and investigate mechanism underlying formation and enhanced catalytic activity and stability under different experimental parameters. The HNFs formed of LPO enzyme purified from bovine milk and copper ions (Cu(2+)) were synthesized at two different temperatures (+4 °C and 20 °C) in PBS (pH 7.4). The effects of experimental conditions, pH and storage temperatures, on the activity and stability of LPO-copper phosphate HNFs were evaluated using guaiacol as a substrate in the presence of hydrogen peroxide (H2O2). Optimum pHs were determined as pH 8 and pH 6 for LPO-copper phosphate HNF and free LPO, respectively. LPO-copper phosphate HNF has higher activity than free LPO at each pHs. Activities of LPO-copper phosphate HNF at pH 6 and pH 8 were calculated as 70.48 EU/mg, 107.23 EU/mg, respectively while free LPO shows 45.78 EU/mg and 30.12 EU/mg, respectively. Compared with free LPO, LPO-copper phosphate HNFs exhibited ∼160% and ∼360% increase in activities at pH 6 and pH 8, respectively. Additionally, LPO-copper phosphate HNFs displayed perfect reusability after six cycles. Finally, we demonstrated that LPO-copper phosphate HNFs can be utilized as a nanosensor for detection of dopamine and epinephrine.

Synthesis of urease hybrid nanoflowers and their enhanced catalytic properties

Increasing numbers of materials have been extensively used as platforms for enzyme immobilization to enhance catalytic activity and stability. Although stability of enzyme was accomplished with immobilization approaches, activity of the most of the enzymes was declined after immobilization. Herein, we synthesize the flower shaped-hybrid nanomaterials called hybrid nanoflower (HNF) consisting of urease enzyme and copper ions (Cu(2+)) and report a mechanistic elucidation of enhancement in both activity and stability of the HNF. We demonstrated how experimental factors influence morphology of the HNF. We proved that the HNF (synthesized from 0.02mgmL(-1) urease in 10mM PBS (pH 7.4) at +4°C) exhibited the highest catalytic activity of ∼2000% and ∼4000% when stored at +4°C and RT, respectively compared to free urease. The highest stability was also achieved by this HNF by maintaining 96.3% and 90.28% of its initial activity within storage of 30 days at +4°C and RT, respectively. This dramatically enhanced activity is attributed to high surface area, nanoscale-entrapped urease and favorable urease conformation of the HNF. The exceptional catalytic activity and stability properties of HNF can be taken advantage of to use it in fields of biomedicine and chemistry.

Purification and Biochemical Characterization of Peroxidase Isolated from White Cabbage (Brassica Oleracea var. capitata f. alba)

Peroxidase enzyme was purified for the first time from white cabbage (Brassica oleracea var. capitata f. alba) in a single step using affinity chromatography and some biochemical characteristics of the purified enzyme were determined. The peroxidase was purified 24.7-fold with an overall recovery of 4.3% and a specific activity of 964.5. The molecular weight of the purified peroxidase was approximately 73.2 kDa as calculated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and it showed maximum activity at pH 6.5 and 30°C. For the guaiacol substrate, the KM and Vmax values were found as 3.19 mM and 0.2 EU/mL, respectively. Additionally, the IC50 and Ki values were determined as 0.517 and 0.994 ± 0.453 mM, respectively, for 4-aminobenzohydrazide. 4-amino benzohydrazide showed non-competitive inhibition.

Egg white hybrid nanoflower (EW-hNF) with biomimetic polyphenol oxidase reactivity: Synthesis, characterization and potential use in decolorization of synthetic dyes

In this study, for the first time, we described organic-inorganic hybrid nanoflowers using crude egg white as the organic component and copper (II) ions as the inorganic component under the mild conditions. The synthesized egg white-inorganic hybrid nanoflowers (EW-hNFs) were characterized using SEM, EDX, XRD and FTIR analysis. The biomimetic Polyphenol/Peroxidase like activities of synthesized egg white-inorganic hybrid nanoflowers (EW-hNFs) were determined by using various phenolics with or without H2O2. Optimum pH and temperature, kinetic parameters, reusability, pH and thermal stability of EW-hNFs were also studied. The most noteworthy aspect of our study is that synthesized EW-hNFs which consist of only egg white proteins, showed polyphenol oxidase activity. Furthermore, potential use of the EW-hNFs in the discoloration of the some synthetic dyes was also evaluated.

Proteinase K hybrid nanoflowers (P-hNFs) as a novel nanobiocatalytic detergent additive

In this study, enzyme-inorganic hybrid nanoflowers were synthesized using proteinase K and Cu2+ ions. The synthesized proteinase K-Cu2+ hybrid nanoflowers (P-hNFs) were characterized by their morphology and chemical point of view by using different techniques such as SEM, FTIR, EDX, and XRD. The proteolytic activities and some important characteristics such as optimum pH and temperature of the P-hNFs were also evaluated by comparison with free proteinase K. Optimum pH values of free proteinase K and P-hNFs were determined as pH 10 and pH 11, respectively. Optimum temperatures recorded for both free proteinase K (at pH 10) and P-hNFs (at pH 11) were 40 °C. In our study, for the first time, using some commercial detergents and surfactants, the utility of the P-hNFs as a detergent additive was also systematically evaluated. In these studies, the P-hNFs exhibited better activity than free proteinase K in the presence of all surfactants (CHAPS, DOC, SDS, Triton X-100 and Tergitol) except for Tween 80. Importantly, the P-hNFs was more stable and compatible with all tested solid laundry detergents. The findings demonstrated that the P-hNFs could potentially be used as an additive in detergent formulations.

The effect of synthesis conditions on enzymatic activity of metal ion incorporated enzyme based hybrid nanoflowers

R oxide supports often exhibit a higher catalytic activity than the stoichiometric surface. Examples are production of liquid fuels from lignocellulose or CO oxidation to CO2. Despite the very different reactions, the catalysts are similar: Ru/TiO2 and Ru/ZrO2 in biomass conversion and Au/TiO2 and Au/ZrO2 in CO oxidation. The common denominator is that removing oxygen from the oxide surface, with formation of oxygen vacancies, results in enhanced catalytic activity. The reasons are clearly identified by studying, with a density functional theory approach, the profile for the reactions where a reduced surface gives lower barriers. However, while TiO2 is a reducible oxide, ZrO2 is not, at least if based on measures of bulk reducibility. We will show that several mechanism, in particular nano-structuring and formation of metal/oxide interfaces can drastically change the surface chemistry of an oxide making zirconia reducible and as active as titania in catalysis by oxides.Statement of the Problem: Transistors and other optoelectronic devices are mainly responsible for the great technological advances in recent years. Although, the improvement of their performances is a goal pursued still. Organic thin-film transistor (OTFT’s) and organic field-effect transistor (OFET’s) showed low carrier mobility and operational overvoltage which decrease their effectiveness and, in many cases, this is attributed to “pinholes” on the gate-dielectric interface. This effect is canceled by using a polymer as gate insulator.T aim of this paper is to present the latest tribological data concerning the mechanism of protective film formation by fuels containing synthetic hydrocarbons and alcohols. The fuels were tested using HFRR and BOCLE methods. The criterion for fuel lubricity in the HFRR and BOCLE tests was the ball wear. The HFRR tester was also capable of measuring the film thickness. The analyzed fuels for diesel and turbine engines consisted of mineral fuel and three series of synthetic compounds, i.e., paraffinic hydrocarbons with an even number of carbon atoms in the chain, paraffinic hydrocarbons with an odd number of carbon atoms and isomers of butanol. The synthetic compounds were added to the mineral fuel at a concentration of 0-20% (v/v). All the fuels tested contained commercially available lubricating additives (carboxylic acids). The addition of the synthetic compounds to the mineral fuel had two effects: diluting the lubricating additives and changing the intermolecular interactions of the base fuel (with no additive). Both effects were considered while analyzing the test results. The experimental data were studied taking into account the conclusions drawn from the αi model described by Kajdas, Kulczycki and Ozimina. The analysis revealed that the liquid phase i.e., the protective film should consist of agglomerates or clusters of hydrocarbon molecules, which are responsible for the transfer of energy in the form of electrons triboemitted from a metal surface to the molecules of the lubricating additives. The proposed mechanism can explain the influence of the base fuel on the effectiveness of the lubricating additives.