Graphene oxide integrated sensor for electrochemical monitoring of mitomycin C-DNA interaction

We present a graphene oxide (GO) integrated disposable electrochemical sensor for the enhanced detection of nucleic acids and the sensitive monitoring of the surface-confined interactions between the anticancer drug mitomycin C (MC) and DNA. Interfacial interactions between immobilized calf thymus double-stranded (dsDNA) and anticancer drug MC were investigated using differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) techniques. Based on three repetitive voltammetric measurements of 120 μg mL(-1) DNA immobilized on GO-modified electrodes, the RSD % (n = 3) was calculated as 10.47% and the detection limit (DL) for dsDNA was found to be 9.06 μg mL(-1). EIS studies revealed that the binding of the drug MC to dsDNA leads to a gradual decrease of its negative charge. As a consequence of this interaction, the negative redox species were allowed to approach the electrode, and thus increase the charge transfer kinetics. On the other hand, DPV studies exploited the decrease of the guanine signal due to drug binding as the basis for specifically probing the biointeraction process between MC and dsDNA.     

The Comparison of Electrochemical Assay and Agarose Gel Electrophoresis for the Determination of DNA Damage Induced by Kainic Acid

A possible DNA damage after interaction of kainic acid (KA) with calf thymus double stranded DNA and genomic DNA was herein determined in in vitro and in vivo conditions using; electrochemical assay and agarose gel electrophoresis. The changes in guanine signal were detected as an indicator of DNA damage in genomic DNA samples isolated from 1 or 10 mg/kg KA‐treated animals. The decreased levels of guanine signal were found as 29% and 33% by 1 and 10 mg/kg KA treatment when compared to controls, respectively. The results of gel electrophoresis confirmed DNA damage obtained in identical samples by electrochemical method.     

Gas chromatographic–mass spectrometric analysis of volatiles obtained by four different techniques from Salvia rosifolia Sm., and evaluation for biological activity

Four different isolation techniques, conventional hydrodistillation (HD), microwave-assisted hydrodistillation (MWHD), microdistillation (MD) and micro-steam distillation-solid-phase microextraction (MSD-SPME), have been used to analyze the volatile constituents from the aerial parts of Salvia rosifolia Sm. by gas chromatography and gas chromatography coupled to mass spectrometry. HD and MWHD techniques produced quantitatively (yield, 0.39% and 0.40%) and qualitatively (aromatic profile) similar essential oils. α-Pinene (15.7–34.8%), 1,8-cineole (16.6–25.1%), β-pinene (6.7–13.5%), β-caryophyllene (1.4–5.0%) and caryophyllene oxide (1.4–4.4%) were identified as major constituents of this Turkish endemic species. Besides, the hydrodistilled oil of S. rosifolia was evaluated for antibacterial, antifungal, anticancer, antioxidant and cytotoxic activities. The hydrodistilled oil of S. rosifolia showed antibacterial activity against Methicillin-resistant Staphylococcus aureus (MRSA) with a MIC value of 125 μg/mL. Other human pathogenic microorganisms (Escherichia coli, Pseudomonas aeruginosa, Enterobacter aerogenes, Salmonella typhimurium, Staphylococcus epidermidis, Candida albicans) were also inhibited within a moderate range (MIC = 125–1000 μg/mL). Antifungal activity of the oil was also observed against the strawberry anthracnose-causing fungal plant pathogens Colletotrichum acutatum, C. fragariae and C. gloeosporioides. No cytotoxicity was observed for S. rosifolia oil up to 25 mg/mL against malignant melanoma, epidermal, ductal and ovary carcinoma.     

The synthesis of some new imidazole and triazole derivatives: crystal Structure and DFT-TDDFT investigation on electronic structure

A series of new N′-3-(1H-imidazol-1-yl)propylcarbamoyl-4-halogenebenzo hydrazonate (3a–b) were obtained by reaction Ethyl 2-((4-halogene phenyl) (ethoxy) methylene) hydrazinecarboxylate (1) and N-(3-aminopropyl)imidazole (2) at 120–140 °C. Compounds (4a–b) were obtained by the reaction compound 1 and N-(3-aminopropyl)imidazole (2) at 160–180 °C. The structures of compounds 3,4 have been inferred through UV–Vis, IR, ¹H/¹³C NMR, mass spectrometry, elemental analyses, and X-ray crystallography. DFT level 6-31G (d) calculations provided structural information. The electronic structure of compound 3a has been studied by DFT level 6-31G (d) calculations using the X-ray data. The results are accordance with X-ray data.     

Quantification of 2-acetyl-1-pyrroline in rice by stable isotope dilution assay through headspace solid-phase microextraction coupled to gas chromatography-tandem mass spectrometry

A new and convenient synthesis of 2-acetyl-1-pyrroline (2AP), a potent flavor compound in rice, and its ring-deuterated analog, 2-acetyl-1-d₂-pyrroline (2AP-d₂), was reported. A stable isotope dilution assay (SIDA), involving headspace solid-phase microextraction (HS-SPME) combined with gas chromatography-positive chemical ionization-ion trap-tandem mass spectrometry (GC-PCI-IT-MS-MS), was developed for 2AP quantification. A divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) fiber was used for HS-SPME procedure and parameters affecting analytes recovery, such as extraction time and temperature, pH and salt, were studied. The repeatability of the method (n = 10) expressed as relative standard deviation (RSD) was 11.6%. A good linearity was observed from 5.9 to 779 ng of 2AP (r² = 0.9989). Limits of detection (LOD) and quantification (LOQ) for 2AP were 0.1 and 0.4 ng g⁻¹ of rice, respectively. The recovery of spiked 2AP from rice matrix was almost complete. The developed method was applied to the quantification of 2AP in aerial parts and grains of scented and non-scented rice cultivars.     

An ITO Based Disposable Biosensor for Ultrasensitive Analysis of Retinol Binding Protein

A highly sensitive electrochemical biosensor based on anti‐RBP biorecognition capable to analyze concentrations of retinol binding protein (RBP) was developed. The construction of the biosensor interfaces was carefully characterized by techniques such as electrochemistry, EIS, and scanning electron microscopy. In order to characterize impedance data, Kramers‐Kronig Transform was performed on the experimental impedance data. Besides, for an immunosensor system the Single Frequency Impedance technique was firstly used for the characterization of the interaction between RBP and anti‐RBP. Finally, artificial serum samples spiked with RBP were analyzed by the proposed ITO based immunosensor to investigate the usefulness of the biosensor for early biomarker diagnosis.     

Magneto-optical specifications of Rosen-Morse quantum dot with screw dislocation

This is the first study to consider a quantum dot with screw dislocation that has Rosen-Morse (RM) confinement potential, generated by a GaAs/GaAlAs heterostructure. An external magnetic field and Aharonov-Bohm (AB) flux field were also applied on RM quantum dot (RMQD) in order to stave the effects of a screw dislocation defect. The combined effect of the screw dislocation defect, the external magnetic field, and AB flux field on the total refractive index changes (TRICs) and the total absorption coefficients (TACs) of RMQD are thus investigated. Cylindrical coordinates are used due to the direction of application of the torsion and the external fields, as well as due to the structure's symmetry. The effective mass approximation and tridiagonal matrix methods are used in order to obtain the subband energy spectra and electronic wave functions of RMQD. The nonlinear optical specifications of RMQD are checked using compact-density-matrix formalism within the framework of the iterative method. Reviews without screw dislocation are also carried out in order to be able to clarify the effects of a screw dislocation defect on the optical properties, and then, both cases are deliberated. This study is the first attempt to analyze the AB flux field for RMQD without screw dislocation. In the present study, the influences of a screw dislocation defect on RMQD's TRICs and TACs are probed by considering different values of the external magnetic field and AB flux field, and the ranges of corresponding parameters on the optimum of the structure are specified. Moreover, the study also elucidates how to rule out the effects of screw dislocation on optical specifications by means of the external fields. Despite a certain screw dislocation, the frequency range is determined where the structure behaves as if it is perfect (namely, without screw dislocation) for its optimum, which in turn is crucial for experimental applications.     

Catalyst functional group cooperativity in the amino acid-catalysed nitroaldol condensation reaction

Several amino acids and their derivatives have been evaluated as organic catalysts for the nitroaldol reaction. It was found that when an unprotected amino group and an unprotected carboxylate group were present in the organocatalyst, both the nitroaldol reaction and subsequent elimination could occur to afford nitroalkenes from aromatic aldehydes and nitromethane. The best results were obtained by use of γ-amino acids derived from l-glutamine. It is suggested that the amino group is important for intermediate Schiff base formation and that the free carboxylate group facilitates the elimination step.     

Structural characterization of heparins from different commercial sources

Seven commercial heparin active pharmaceutical ingredients and one commercial low molecular weight from different manufacturers were characterized with a view profiling their physicochemical properties. All heparins had similar molecular weight properties as determined by polyacrylamide gel electrophoresis (M _N, 10–11 kDa; M _W, 13–14 kDa; polydispersity (PD), 1.3–1.4) and by size exclusion chromatography (M _N, 14–16 kDa; M _W, 21–25 kDa; PD, 1.4–1.6). one-dimensional ¹H- and ¹³C-nuclear magnetic resonance (NMR) evaluation of the heparin samples was performed, and peaks were fully assigned using two-dimensional NMR. The percentage of glucosamine residues with 3-O-sulfo groups and the percentage of N-sulfo groups and N-acetyl groups ranged from 5.8–7.9%, 78–82%, to 13–14%, respectively. There was substantial variability observed in the disaccharide composition, as determined by high performance liquid chromatography (HPLC)-mass spectral analysis of heparin lyase I–III digested heparins. Heparin oligosaccharide mapping was performed using HPLC following separate treatments with heparin lyase I, II, and III. These maps were useful in qualitatively and quantitatively identifying structural differences between these heparins. The binding affinities of these heparins to antithrombin III and thrombin were evaluated by using a surface plasmon resonance competitive binding assay. This study provides the physicochemical and activity characterization necessary for the appropriate design and synthesis of a generic bioengineered heparin.     

Hyphenated techniques for the analysis of heparin and heparan sulfate

The elucidation of the structure of glycosaminoglycan has proven to be challenging for analytical chemists. Molecules of glycosaminoglycan have a high negative charge and are polydisperse and microheterogeneous, thus requiring the application of multiple analytical techniques and methods. Heparin and heparan sulfate are the most structurally complex of the glycosaminoglycans and are widely distributed in nature. They play critical roles in physiological and pathophysiological processes through their interaction with heparin-binding proteins. Moreover, heparin and low-molecular weight heparin are currently used as pharmaceutical drugs to control blood coagulation. In 2008, the health crisis resulting from the contamination of pharmaceutical heparin led to considerable attention regarding their analysis and structural characterization. Modern analytical techniques, including high-performance liquid chromatography, capillary electrophoresis, mass spectrometry, and nuclear magnetic resonance spectroscopy, played critical roles in this effort. A successful combination of separation and spectral techniques will clearly provide a critical advantage in the future analysis of heparin and heparan sulfate. This review focuses on recent efforts to develop hyphenated techniques for the analysis of heparin and heparan sulfate.