Application of affinity microspheres for effective SPE cleanup before the determination of sulfamerazine by HPLC.

This paper describes the application of poly (ethylene glycol dimethacrylate-N-methacryloyl-L-tryptophane methyl ester) [p(EGDMA-MATrp)] microspheres as an affinity sorbent for the SPE (solid phase extraction) cleanup of sulfamerazine (SMR) from food samples of animal origin before high performance liquid chromatography (HPLC) analysis. The microspheres were prepared by suspension polymerization of ethylene glycol dimethacrylate (EGDMA) and N-methacryloyl-L-tryptophane methyl ester (MATrp) as a crosslinker and a monomer, respectively. Various parameters affecting the SPE cleanup efficiency of the p(EGDMA-MATrp) microspheres (contact time, pH, initial SMR concentration, ionic strength etc.) were optimized. Under the optimized conditions, maximum adsorption capacity was found to be 8.55 ±â€¯0.44 mg/g sorbent at pH 5.0. 90% of the adsorbed SMR was desorbed by using ACN:MeOH (5:5) mixture as a desorption agent. Applicability of the microspheres for the SPE cleanup of SMR residues in the food samples such as egg and milk with HPLC was also determined. It was demonstrated that the prepared p(EGDMA-MATrp) microspheres could be repeatedly applied for SPE cleanup of sulfamerazine before chromatographic analysis. Also, the recoveries of SMR in milk and egg samples were reasonably satisfactory and in the range of 71 to 90%.

Oxime-functionalized cryogel disks for catalase immobilization.

Catalase is a protective enzyme against oxidative stress and converts hydrogen peroxide into water and molecular oxygen. In the current study, catalase immobilization was applied onto the oxime-functionalized cryogel disks. Cryogel disks were produced by free radical polymerization. After cutting as circular disks, oxime ligand (4-biphenylchloroglyoxime, BPCGO) was attached and oxime-functionalized cryogel disks were obtained. After optimization of several immobilization parameters such as pH, initial catalase concentration, temperature and ionic strength, maximum catalase load was detected as 261.7 ± 11.2mg/g for cryogel disk at pH5.0. Activity studies indicated that immobilization enhanced the enzyme activity in basic pH region, the temperature range of 15-35°C and at ionic strengths between 0.2 and 1.0M NaCl. Km was detected as 9.9 and 11.0mM and Vmax was 357.1 and 769.2µmol min-1 for free and immobilized catalase, respectively. kcat and Km/kcat values showed that immobilization enhanced the catalytic efficiency. Storage stability experiments demonstrated that immobilization increased the usability period. Furthermore, catalase desorption was achieved by 1.0M NaSCN at pH8.0 successfully and catalase adsorption capacity of oxime-functionalized cryogel disk was decreased by 9.9% at the end of 5 adsorption-desorption cycle.

Persistent organochlorine residues in fish and sediments collected from Eastern Aegean coast: Levels, occurrence and ecological risk.

Organochlorines were determined in fish and sediment collected from Izmir and Çandarli Bays. The results indicated that ΣCyclodiens were generally predominant contaminants. In all samples, p,p'-DDE was the predominant DDT congener. Aroclors were found in noticeably higher levels than OCPs in sediment and the highest levels of Aroclors, OCPs were found in Nemrut which can be attributed to industrial activities. According to Sediment Quality Guidelines, DDTs were lower than the values that may cause adverse biological risk in sediment samples. Aroclor 1254 in sediments only exceeded the TEL value at Nemrut site. The maximum values of ΣOCPs were found in fish collected from Gülbahçe, while Aroclors were measured in Aliaga. According to related indices, results indicate no recent influxes of DDT in the sampling areas. The estimated daily intake of DDTs, Aroclor1254 were below the acceptable daily intake level recommended by FAO/WHO.

Selective cholesterol adsorption by molecular imprinted polymeric nanospheres and application to GIMS.

Molecular imprinted polymers (MIPs) are tailor-made materials with selective recognition to the target. The goals of this study were to prepare cholesterol imprinted polymeric nanospheres (CIPNs) and optimize their adsorption parameters and also to use CIPNs for adsorption of cholesterol (CHO), which is an important physiological biomacromolecule, from gastrointestinal mimicking solution (GIMS). Pre-polymerization complex was prepared using CHO as template and N-methacryloylamido-(l)-phenylalanine methyl ester (MAPA). This complex was polymerized with 2-hydroxyethyl methacrylate (HEMA). CHO was removed by MeOH and tetrahydrofuran (THF). Adsorption studies were performed after chacterization studies to interrogate the effects of time, initial concentration, temperature, and ionic strength on CHO adsorption onto CIPNs. Maximum adsorption capacity (714.17mg/g) was higher than that of cholesterol imprinted polymers in literature. Pseudo-second-order kinetics and Langmuir isotherm fitted best with the adsorption onto CIPNs. 86% of adsorbed cholesterol was desorbed with MeOH:HAc (80:20, v/v) and CIPNs were used in adsorption-desorption cycle for 5-times with a decrease as 12.28%. CHO analogues; estron, estradiol, testosterone, and progesterone were used for competitive adsorption. The relative selectivity coefficients of CINPs for cholesterol/estron and cholesterol/testosterone were 3.84 and 10.47 times greater than the one of non-imprinted polymeric nanospheres (NIPNs) in methanol, respectively.

A novel affinity disks for bovine serum albumin purification.

The adsorption characteristics of bovine serum albumin (BSA) onto the supermacroporous poly(hydroxyethylmethacrylate)-Reactive Green 19 [p(HEMA)-RG] cryogel disks have been investigated in this paper. p(HEMA) cryogel disks were prepared by radical polymerization initiated by N,N,N',N'-tetramethylene diamine (TEMED) and ammonium persulfate (APS) pair in an ice bath. Reactive Green (RG) 19 was covalently attached to the p(HEMA) cryogel disks. These disks were used in BSA adsorption studies to interrogate the effects of pH, initial protein concentration, ionic strength, and temperature. BSA adsorption capacity of the p(HEMA)-RG cryogel disk was significantly improved after the incorporation of RG. Adsorption capacity reached a plateau value at about 0.8 mg/mL at pH 4.0. The amount of adsorbed BSA decreased from 37.7 to 13.9 mg/g with increasing NaCl concentration. The enthalpy of BSA adsorption onto the p(HEMA)-RG cryogel disk was calculated as -58.4 kJ/mol. The adsorption equilibrium isotherm was fitted well by the Freundlich model. BSA was desorbed from cryogel disks (over 90 %) using 0.5 M NaSCN, and the purity of desorbed BSA was confirmed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The experimental results showed that the p(HEMA)-RG cryogel disks have potential for the quick protein separation and purification process.

Use of magnetic poly(glycidyl methacrylate) monosize beads for the purification of lysozyme in batch system.

The hydrophobic affinity ligand L-tryptophan immobilized magnetic poly(glycidyl methacrylate) [m-poly(GMA)] beads in monosize form (1.6 microm in diameter) were used for the affinity purification of lysozyme from chicken egg white. The m-poly(GMA) beads were prepared by dispersion polymerization in the presence of Fe3O4 nano-powder. The epoxy groups of the m-poly(GMA) beads were converted into amino groups with 1,6 diaminohexane (i.e., spacer arm). l-tryptophan was then covalently immobilized on spacer arm attached m-poly(GMA) beads. Elemental analysis of immobilised L-tryptophan for nitrogen was estimated as 42.5 micromol/g polymer. Adsorption studies were performed under different conditions in a batch system (i.e., medium pH, protein concentration and temperature). Maximum lysozyme adsorption amount of m-poly(GMA) and m-poly(GMA)-L-tryptophan beads were 1.78 and 259.6 mg/g, respectively. The applicability of two kinetic models including pseudo-first order and pseudo-second order model was estimated on the basis of comparative analysis of the corresponding rate parameters, equilibrium adsorption capacity and correlation coefficients. Results suggest that chemisorption processes could be the rate-limiting step in the adsorption process. It was observed that after 10 adsorption-elution cycle, m-poly(GMA)-L-tryptophan beads can be used without significant loss in lysozyme adsorption capacity. Purification of lysozyme from egg white was also investigated. Purification of lysozyme was monitored by determining the lysozyme activity using Micrococcus lysodeikticus as substrate. It was found to be successful in achieving purification of lysozyme in a high yield of 76% with a purification fold of 71 in a single step. The specific activity of the eluted lysozyme (62,580 U/mg) was higher than that obtained with a commercially available pure lysozyme (Sigma (60,000 U/mg).

Removal of chlorophenols from aquatic systems using the dried and dead fungus Pleurotus sajor caju.

In this study, the potential use of the fungus Pleurotus sajor caju to remove phenols (i.e., phenol, o-chlorophenol, p-chlorophenol and 2,4,6-trichlorophenol) from aqueous solutions was evaluated. Biosorption of phenol or chlorophenols reached equilibrium in 4 h. The maximum adsorptions of phenol and chlorophenols onto the Pleurotus sajor caju were 0.95 mmol/g for phenol, 1.24 mmol/g for o-chlorophenol, 1.47 mmol/g for p-chlorophenol and 1.89 mmol/g for 2,4,6-trichlorophenol. The affinity order was as follows: 2,4,6-trichlorophenol> p-chlorophenol> o-chlorophenol>phenol. Phenol and chlorophenols bindings onto Pleurotus sajor caju were clearly pH dependent. The adsorption of phenol and chlorophenols increased with increasing pH. Desorption was achieved using methanol solution (30%, v/v). Pleurotus sajor caju biomass is suitable for reuse for more than five cycles without noticeable loss of adsorption capacity.

Effect of functional pinealectomy on hippocampal lipid peroxidation, antioxidant enzymes and N-methyl-D-aspartate receptor subunits 2A and 2B in young and old rats.

OBJECTIVES: To investigate the effects of pinealectomy on lipid peroxidation, antioxidant status and NMDA receptor subunits 2A and 2B concentrations in hippocampus. DESIGN: Forty-eight male Wistar-albino rats were used. SETTINGS: Animals were divided into three groups: 24 h dark throughout the study (highest melatonin release), 24 h light exposure (light-induced functional pinealectomy) and 12 h light/12 h dark exposure (control group). Thereafter, each group was divided into two groups as young and old animals. RESULTS: There was an increase in NR2A and NR2B concentration in DY group compared to all other treatments. CuZn and Mn SOD activities were found to be increased in CO compared to CY group. Continual light exposure for 4 weeks did not change neural CuZn and Mn SOD activities. In old rats, light exposure reduced the activities of both CuZn and Mn SOD relative to those in the young animals. In addition, CuZn and Mn SOD activities were higher in dark exposed rats than in those in the continual light exposed or LD 12:12 rats. GSH-Px activity was found elevated in the DY rats compared to the CY groups. MDA levels were significantly higher in the CO than in the CY group. CONCLUSIONS: NR2A and NR2B receptor concentrations in hippocampus of the rats maintained in dark showed significant increases compared to the control and functional pinealectomy groups but there was no significant increase in lipid peroxidation.