Elif Demirkan

Synthesis, crystal structure, stability studies, DNA/albumin interactions, and antimicrobial activities of two Cu(II) complexes with amino acids and 5-nitro-1,10-phenanthroline

Abstract One-dimensional (1-D) coordination polymer and mononuclear copper(II) complexes, ([Cu(nphen)(asn)]ClO4)n (1) and [Cu(nphen)(gln)(H2O)]ClO4·H2O (2) (nphen = 5-nitro-110-phenanthroline, asn = asparagine, gln = glutamine), have been synthesized and characterized by IR spectroscopy, ESI-MS, CHN analysis, and single-crystal X-ray diffraction. These binary and ternary complexes of copper(II) with nphen, asn, and gln have been investigated using potentiometric methods in 0.1 M KCl aqueous ionic media at 298.2 K. The protonation constants of the ligands and the stability constants of 1 and 2 have been calculated from the potentiometric data using the “BEST” software package. The potentiometric results have been analyzed using the “SPE” software package, and the distribution curves for the copper-containing species have been determined for the ternary systems. The CT-DNA-binding properties of these complexes have been investigated by thermal denaturation measurements and both absorption and emission spectroscopy. Further, the interaction of these complexes with bovine serum albumin (BSA) and human serum albumin (HSA) has been investigated using absorption and emission spectroscopy. The thermodynamic parameters, free energy change (ΔG), enthalpy change (ΔH), and entropy change (ΔS) were calculated by the van’t Hoff equation and discussed. The distances between the serum albumins and 1 and 2 have been obtained according to fluorescence resonance energy transfer (FRET). Conformational changes of serum albumins have been observed from synchronous fluorescence technique. The antimicrobial activity of the complexes has also been tested on some bacteria. The effect of different amino acids on the copper(II) complexes are discussed.

Inhibition of quorum sensing-controlled virulence factors in Pseudomonas aeruginosa by human serum paraoxonase.

The role of quorum sensing (QS) in the regulation of virulence factor production in Pseudomonas aeruginosa is well established. Increased antibiotic resistance in this bacterium has led to the search for new treatment options, and inhibition of the QS system has been explored for potential therapeutic benefits. If the use of QS inhibitory agents were to lead to a reduction in bacterial virulence, new approaches in the treatment of P. aeruginosa infections could be further developed. Accordingly, we examined whether human serum paraoxonase 1 (hPON1), which uses lactonase activity to hydrolyse N-acyl homoserine lactones, could cleave P. aeruginosa-derived signalling molecules. hPON1 was purified using ammonium sulfate precipitation and hydrophobic interaction chromatography (Sepharose 4B-L-tyrosine-1-naphthylamine). Different concentrations of hPON1 were found to reduce various virulence factors including pyocyanin, rhamnolipid, elastase, staphylolytic LasA protease and alkaline protease. Although treatment with 0.1-10 mg hPON1 ml(-1) did not show a highly inhibitory effect on elastase and staphylolytic LasA protease production, it resulted in good inhibitory effects on alkaline protease production at concentrations as low as 0.1 mg ml(-1). hPON1 also reduced the production of pyocyanin and rhamnolipid at a concentration of 1.25 mg ml(-1 )(within a range of 0.312-5 mg ml(-1)). In addition, rhamnolipid, an effective biosurfactant reported to stimulate the biodegradation of hydrocarbons, was able to degrade oil only in the absence of hPON1.

Protease immobilization on cellulose monoacetate/chitosan-blended nanofibers:

Chitosan-blended cellulose monoacetate nanofibers were prepared through electrospinning process. Neat nanofibers and their sodium hydroxide-treated analogs were used as support surfaces for protease immobilization via physical adsorption method. Morphologies of the nanofibers were observed with a scanning electron microscopy. Chemical analyses were conducted with Fourier transform infrared spectroscopy, and thermal analyses were carried out with differential scanning calorimeter and thermogravimetric analyzer. Immobilized enzyme activities were measured by using casein substrate. In order to test the stability of immobilized enzymes, the tests were repeated until the immobilized enzyme activity was leveled off. The results reveal that well uniform cellulose monoacetate/chitosan nanofibers were obtained, and nanofiber structures are transformed from rounded to more flattened morphology after enzyme activation test. Glutaraldehyde activation has positive effect on sodium hydroxide-treated samples, and the highest immobilization yield as about 83% was observed for glutaraldehyde-treated cellulose monoacetate/chitosan samples. Sodium hydroxide treatment before glutaraldehyde activation shows the best results for protease immobilization on cellulose monoacetate and cellulose monoacetate/chitosan nanofibers. Operational stability increases after sodium hydroxide treatment and glutaraldehyde activation. Glutaraldehyde activation effectively increased the cycle number after sodium hydroxide treatment and about 20% of enzyme activity was still retained after seven cycles at cellulose monoacetate/chitosan samples. This percentage is higher at pure cellulose monoacetate nanofibers than cellulose monoacetate/chitosan nanofibers and measured around 33.5%.

Partial purification, characterization and wheat bran degradation studies of a new phytase from the Bacillus megaterium EBD 9-1 strain

Abstract Objective: The present study was designed to report the bacterial identification and characterization of a new phytase enzyme from a Bacillus sp. strain isolated from soil. Methods: Bacillus sp. strain was identified based on 16S rRNA analysis. The phytase was partially purified through ammonium sulfate precipitation and Sephadex G100 gel filtration steps, and characterized for its activity and stability. Results: The new isolate EBD 9-1 showed 100% sequence identity with Bacillus megaterium. The partially purified enzyme had the maximum activity at pH 7.0 and 60°C. The activity of the enzyme was stimulated in the presence of Ca+2, Vmax and Km for enzyme were found to be 333 U/mL and 2 mM, respectively. The estimated molecular weight of enzyme was 45 kDa. The storage stability of phytase was 93% of the initial activity after 6 months at 4°C and −20°C. This study represents the partial purification, characterization and wheat bran degradation studies for B. megaterium phytase. Conclusion: Consequently, due to the characteristics such as significant stability at higher temperatures, alkaline pH and storage of the novel phytase enzyme produced by B. megaterium EBD 9-1, the enzyme may be suitable for supplementing animal feeds to improve the availability of phosphorus from phytates.

Antimicrobial activities of seed extracts of Prunus persica, Prunus cerasus, Prunus avium and Prunus armeniaca

G tenax (Forssk.) Fiori. (Malvaceae) is commonly found in Africa, Asia and Australia. It has been used traditionally to treat various diseases. The extracts from various plants, which are expected to be safe, exhibited various biological effects, e.g., anti-oxidant, antibacterial, hepatoprotective, anti-inflammatory, anti-emetic, anti-malarial, analgesic, and anti-pyretic activities. Such effects might be attributed to the flavonoidal content of the species, e.g., quercetin. A total of 25 accessions of G. tenax were selected for this study from trees grown within the same geographical area. Seven morphological traits were measured for each accession. Three phenotypes were identified according to their distinct variations in leaf and stem morphology. Air dried leaves and stem were extracted separately using 80% methanol. The methanolic extracts were fractionated sequentially using petroleum ether, dichloromethane and ethyl acetate. Phytochemical analysis was carried out to detect variations in quercetin content in leaves and stems within the phenotypes. A reversed-phase ultra-performance liquid chromatography, using an ultraviolet diode array detector (RP-UPLC-UV/DAD) assay was standardized for quercetin detection and quantification in the ethyl acetate fractions. The results showed variation in quercetin contents between different phenotypes, and between leaves and stem. The highest quercetin content (14.09 mg/L) was present in stem of G. tenax phenotype SUST1. These results reinforce the strong phenotypic effect on the secondary chemical profile. The variability in quercetin content in G. tenax might be related to genotypic or parent of origin effects. The clear morphological characters variation measured in studied plants provided a good indicator to distinguish between them in quercetin contents.