Mahmut Toprak

The investigation of the interaction between orientin and bovine serum albumin by spectroscopic analysis

In this paper, the interaction between orientin and bovine serum albumin (BSA) was examined using fluorescence and absorbance spectroscopy. The analysis of the quenching mechanism was done using Stern-Volmer plots which exhibit upward (positive) deviation. A linear response to orientin was shown in the concentration range between 3 and 50 μM. The experimental results showed the presence of a static quenching process between orientin and BSA. The thermodynamic parameters ΔH, ΔS and ΔG were also calculated and suggested that the hydrophobic and electrostatic interactions played an important role in the interaction between orientin and BSA. Furthermore, the distances between BSA and orientin were determined according to Förster non-radiation energy transfer theory. In addition, the results of the synchronous fluorescence obtained indicated that the binding of orientin with BSA could affect conformation in BSA.

Spectroscopic investigations on the binding of Pyronin Y to human serum albumin

The interaction of Pyronin Y with human serum albumin (HSA) has been investigated systematically by fluorescence, absorption, fluorescence decay lifetime measurements, FTIR, synchronous fluorescence spectroscopy, and molecular modeling method. The spectroscopic and fluorescence quenching experiments show that Pyronin Y may show a static quenching mechanism with HSA. The specific binding distance of 1.96 nm between HSA and Pyronin Y was obtained via Förster non-radiation energy transfer method. The thermodynamic parameters indicate that the electrostatic interactions play a significant role during the binding process. In addition, synchronous fluorescence and FT-IR spectra indicated that the conformation and microenvironment of HSA were not influenced with the addition of Pyronin Y. The obtained results can be of biological significance in photodynamic therapy.

Illumination impact on the electrical characterizations of an Al/Azure A/p-Si heterojunction

In this study, we fabricated an Al/Azure A/p-Si heterojunction. The electrical characterization and photovoltaic properties of the Al/Azure A/p-Si heterojunction were investigated by current–voltage (I–V) under dark and illuminated conditions at room temperature. The photovoltaic device gives Voc = 340 mV and Isc = 807 μA under 30 mW cm−2. The device was found to have a fill factor (FF) and power conversion efficiency (ηP) 36% and 4.07%, respectively. The values of some diode parameters were determined using thermionic emission theory. Some diode parameters, such as the ideality factor (n) and barrier height (b) values, were found to be 1.26 and 0.78 eV, respectively. An ideality factor higher than 1 can be explained on the basis of the inhomogeneity barrier-height model or as a result of natural oxide layers. The results obtained from electrical and photovoltaic properties show that the device can be used as photodiode and in opto-electronic circuit applications.

Fluorescence study on the interaction of human serum albumin with Butein in liposomes

The interaction of Butein with human serum albumin in L-egg lecithin phosphatidycholine (PC) liposome has been investigated by fluorescence and absorption spectroscopy. The results of the fluorescence measurement indicated that Butein effectively quenched the intrinsic fluorescence of HSA via static quenching. The Stern–Volmer plots in all the liposome solutions showed a positive deviation from the linearity. According to the thermodynamic parameters, the hydrophobic interactions appeared be the major interaction forces between Butein and HSA. The effect of Butein on the conformation of HSA was also investigated by the synchronous fluorescence under the same experimental conditions. In addition, the partition coefficient of the Butein in the PC liposomes was also determined by using the fluorescence quenching process. The obtained results can be of biological significance in pharmacology and clinical medicine.

Spectroscopic studies on the interaction of fluorescein and safranine T in PC liposomes.

In this study, the fluorescence quenching of fluorescein by safranine T in liposome media had been investigated systematically by fluorescence spectroscopy, UV-vis absorption spectroscopy and fluorescence decay lifetime measurements. The spectroscopic data were analyzed using a Stern-Volmer equation to determine the quenching process. The experimental results showed that the intrinsic fluorescence of fluorescein was strongly quenched by safranine T, and that the quenching mechanism was considered as static quenching by forming a ground-complex. The Stern-Volmer quenching constant Ksv, and the bimolecular quenching constant Kq were estimated. The distances between the donor (fluorescein) and the acceptor (safranine T) were calculated according to the Förster non-radiation energy transfer theory. In addition, the partition coefficient of the safranine T (Kp) in the L-egg lecithin phosphatidylcholine liposomes was also calculated by utilizing the fluorescence quenching.

Removal of Pyronin B from aqueous solutions using raw and modified vermiculite

The raw vermiculite was chemically modified with phosphoric acid and applied as a potential adsorbent for the removal of Pyronin B, a xanthene derivative dye, from aqueous solution. The raw VMT and phosphoric acid-modified vermiculite (P-VMT) samples were examined by XRD, FTIR, TGA, and SEM. The initial raw vermiculite (VMT) has impurities such as calcite, which is completely eliminated after modification. The results showed that the adsorption capacity of P-VMT was found to be higher than VMT. The adsorption equilibrium data were tested by the Langmuir, Freundlich, and Dubinin–Radushkevich isotherm models. The results showed that the adsorption of Pyronin B by vermiculite fitted the Freundlich isotherm well, while that exhibited by P-VMT fitted the Langmuir isotherm well. The adsorption kinetic of Pyronin B onto VMT and P-VMT was described by the pseudo-second-order model. The intra-particle diffusion model indicated that the adsorption may also be followed by multiple adsorption processes. Moreover, the thermodynamic parameters were also calculated. It was determined that the adsorption of Pyronin B on VMT and P-VMT was an endothermic and spontaneous process. The desorption of the dye on VMT and P-VMT using ethanol and methanol was also investigated primarily.