Mevlut Bayrakci

Improvement of catalytic activity of Candida rugosa lipase in the presence of calix[4]arene bearing iminodicarboxylic/phosphonic acid complexes modified iron oxide nanoparticles.

In the present study, iron oxide magnetite nanoparticles, prepared through a co-precipitation method, were coated with phosphonic acid or iminodicarboxylic acid derivatives of calix[4]arene to modulate their surfaces with different acidic groups. Candida rugosa lipase was then directly immobilized onto the modified nanoparticles through sol-gel encapsulation. The catalytic activities and enantioselectivities of the two encapsulated lipases in the hydrolysis reaction of (R/S)-naproxen methyl ester and (R/S)-2-phenoxypropionic acid methyl ester were assessed. The results showed that the activity and enantioselectivity of the lipase were improved when the lipase was encapsulated in the presence of calixarene-based additives; the encapsulated lipase with the phosphonic acid derivative of calix[4]arene had an excellent rate of enantioselectivity against the (R/S)-naproxen methyl and (R/S)-2-phenoxypropionic acid methyl esters, with E=350 and 246, respectively, compared to the free enzyme. The encapsulated lipases (Fe-Calix-N(COOH)) and (Fe-Calix-P) showed good loading ability and little loss of enzyme activity, and the stability of the catalyst was very good; they only lost 6-11% of the enzymes activity after five batches.

Synthesis and Preparation of Novel Magnetite Nanoparticles Containing Calix[4]arenes With Different Chelating Group Towards Uranium Anions

In this study, four new magnetite nanoparticle containing different chelating groups as ester, amide and azacrown moieties at the lower rim of calix[4]arenes were prepared by the reaction of formylated calix[4]arenes and amino propyl modified magnetite nanoparticles (APTMS-MN). All of the newly synthesized and prepared compounds were characterized by using different analytical techniques such as nuclear magnetic resonance spectroscopy (NMR), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM) and thermogravimetric analyses (TGA). Furthermore, uranium binding abilities of newly prepared magnetite nanoparticles were evaluated by using solid-liquid phase extraction process and obtained results showed that magnetite nanoparticles containing picolinamide units exhibited superior and more efficient extraction percentage for uranium ions at lower pH values.

Synthesis and characterization of novel nanofiber based calixarene and its binding efficiency towards chromium and uranium ions

The objective of this study is to obtain nanofibrous precursor based calixarene with high ion adsorption capacity by electrospinning of blended solution of polyacrylonitrile (PAN) and upper rim functionalized calix[4]arene bearing N-methylglucamine (Calix-NMG). The obtained electrospun fibers were characterized using fourier transform infrared (FT-IR-ATR), scanning electron microscope (SEM) equipped with energy-dispersive X-ray spectrometry (EDX) and thermogravimetric analyses (TGA and DSC). Analysis indicated that preparation of nanofibers based Calix-NMG was successfully achieved. The ion binding studies exhibited that the nanofiber based Calix-NMG could be efficiently used for the binding of chromate anions and uranium cations. Nanofiber based calix[4]arene with N-methylglucamine chelating groups may be a good candidate as a filter material for treatment of a large quantity of wastewater owing to their very large surface area as well as both the inclusion and donor–acceptor complexation capability of all surfaces associated with the calixarene skeleton.

Calixarene-engineered surfaces and separation science

After their discovery, calixarenes have attracted the attention of many researchers from various disciplines. This group of supramolecules has an increasing popularity and this is most probably related with the flexibility of calixarene chemistry. Owing to their multifunctional character and stability, calixarenes became important precursors in separation science to derive new-type of sorbents or stationary phases. Immobilization of calixarenes to a suitable solid support (e.g. silica, synthetic polymers, magnetite nanoparticles, etc.) is a very popular concept being used for this purpose, and various immobilization methodologies have been proposed in the literature. In the present work, some state-of-the-art researches and developments published in the past are reviewed in a collective manner, and thus fundamentals of calixarene-immobilization and the application of the obtained materials in sorption and high performance liquid chromatography are represented.

Humic-makeup approach for simultaneous functionalization of polyacrylonitrile nanofibers during electrospinning process, and dye adsorption study

ABSTRACT A useful methodology is represented to functionalize polyacrylonitrile nanofibers by using humic acid as a makeup agent in electrospinning process. Both morphology and surface chemistry of polyacrylonitrile nanofiber mats were understood to be influenced by incorporation of humic acid into the structure. Physicochemical changes were evidenced by Fourier transform infrared spectroscopy, scanning electron microscope, and surface charge measurements. Unlike some anionic dyes (i.e., methyl orange, methyl red, and Congo red), there was an enhancement in crystal violet (a cationic dye) adsorption after incorporation of humic acid. The Langmuir model fitted well to crystal violet data, and monolayer adsorption capacity was calculated as 81.6 mg/g (r2 = 0.998).

Macrocyclic anthracene-anchored calix[4]arene as a sensitive and selective fluorescent chemosensor for ytterbium ions

ABSTRACT A novel anthracene anchored cone calix[4]arene pyridine amide receptor C4PA was synthesized and characterized by combination of spectroscopic and spectrophotometric techniques. Ion binding properties of C4PA towards a series of metal cations were investigated by UV and fluorescence spectra. A remarkable increase for receptor C4PA in fluorescence intensity in the presence of trace amounts of Yb3+ was observed. C4PA showed “turn on” type fluorescence response toward Yb3+ with high selectivity and C4PA also retained its selectivity toward Yb3+ in the presence of most competing metal ions.

Intermolecular interactions and binding mechanism of inclusion complexation between sulfonate calix[ n ]arenes and ethidium bromide

In this work, the interactions between ethidium bromide (ET) and water-soluble sulfonate calix[n]arenes (n: 4, 6, and 8) were investigated by NMR, FT-IR, and fluorescence spectroscopic methods. The aim was to evaluate both the stoichiometry and the mechanism of the possible complex structure between sulfonate calix[n]arenes and ET. The spectroscopic data revealed that a 1:1 binding mode between calixarene and ET was occurred. Furthermore, thermodynamic parameters and fluorescence titration experiments were studied at different temperatures to determine both the quenching mechanism and the type of intermolecular forces in complex formation. Host–guest complexation of sulfonate calix[n]arenes and ET could be used to overcome some adverse effects related to the using of ethidium bromide during biological applications as a DNA marker treatment.

Pesticide binding and urea-induced controlled release applications with calixarene naphthalimide molecules by host–guest complexation

ABSTRACT Three novel calix[4]arene molecule-based 1,8 naphthalimide fluoroionophore for the selective determination of kesoxim-methyl were synthesized and used in pesticide binding studies. The possible interaction between pesticides and fluorescent calix[4]arene molecules was monitored by UV/Vis absorption and fluorescence spectroscopy. When compared the studied pesticides, kesoxim-methyl was strongly quenched the fluorescence intensity of upper rim-modified calix[4]arene. UV and fluorescence titration experiments were also studied to determine both the quenching mechanism and stoichiometric ratio consisted in complex formation. Furthermore, pesticide release experiments were also performed with a fertilizing agent as urea by using fluorescence spectroscopy technique.

Calixarene-immobilized monolithic cryogels for preparative protein chromatography

New cation exchanger monolithic stationary phases were prepared by immobilization of three different calixarene derivatives (i.e. tetracarboxylate calix[4]arene, CLX-COO, tetrasulfonate calix[4]arene, CLX-SO3, and tetraphosphonate calix[4]arene, CLX-PO4) onto a monolithic cryogel support (i.e. poly(2-hydroksyethylmethacrilate-co-glycidyl methacrylate, P) and investigated with respect to preparative protein chromatography. The obtained monoliths were characterized through various techniques such as FTIR spectroscopy, isoelectric point measurements, titrimetric analyses, and mercury intrusion porosimetry. Protein retention was investigated using some model proteins (i.e. lysozyme, cytochrome c, and ɑ-chymotrypsinogen A, human serum albumin, and myoglobin), and the role of modifier (i.e. NaCl) concentration and pH was thoroughly analyzed under isocratic and gradient elution conditions. Overloading experiments were also conducted to study dynamic adsorption capacity and the obtained values were found to be ranging between 3 and 8 mg/mL depending on the type of calixarene molecule. Hence, higher or comparable protein adsorption capacities were seen to be applicable on calixarene-immobilized cryogels when compared to any other functionalized cryogels in the literature. Combined with the favorable properties of these monoliths, with respect to mass transport of large molecules, these results qualify calixarene functionalized monolithic cryogels as promising stationary phases for protein preparative purification.