Kobra Zarei

The present work describes an ultrasensitive electrochemical sensor for determination of mercury(II) using deoxyribonucleic acid/poly-L-methionine-gold nanoparticles/pencil graphite electrode (DNA/PMET-AuNPs/PGE). To fabricate this biosensor, L-methionine (L-MET) was electropolymerized on the PGE surface followed by simultaneous electrochemical entrapment of AuNPs. Next, DNA was immobilized on the PMET-AuNPs/PGE by applying a 0.5 V potential. The surface area of modified and unmodified electrodes was determined by chronocoulometric technique. Hg²⁺ was detected in the linear dynamic range of 0.1 aM to 0.1 nM, and the detection limit was determined as 0.004 aM using square wave anodic stripping voltammetry (SWASV) under optimized conditions. The DNA/PMET-AuNPs/PGE demonstrated good selectivity toward Hg²⁺ against other metal ions such as V⁴⁺, Pb²⁺, Cr³⁺, Cd²⁺, Cu²⁺, Zn²⁺, Sn²⁺, In³⁺, Ge⁴⁺, and Fe³⁺. Real samples studies were carried out in sea water and fish samples. © 2018 Elsevier B.V.

In this paper, an electrochemical sensor was prepared based on the modification of pencil graphite electrode (PGE) by hollow platinum nanoparticles/reduced graphene oxide (HPtNPs/rGO/PGE) for determination of ceftazidime (CFZ). Initially, rGO was electrodeposited on the electrode surface, and then, hollow platinum nanoparticles were placed on the electrode surface via galvanic displacement reaction of Pt(IV) ions with cobalt nanoparticles (CoNPs) that had electrodeposited on the electrode surface. Several significant parameters controlling the performance of the HPtNPs/rGO/PGE were examined and optimized using central composite design as one optimization methodology. The surface morphology and elemental characterization of the bare PGE, rGO/PGE, CoNPs/rGO/PGE, and HPtNPs/rGO/PGE-modified electrodes was analyzed by field-emission scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and electrochemical impedance spectroscopy. The electrochemical activity of CFZ on resulting modified electrode was investigated by cyclic voltammetry (CV) and adsorptive differential pulse voltammetry (AdDPV). Adsorptive differential pulse voltammetry indicates that peak current increases linearly with respect to increment in CFZ concentration. CFZ was determined in the linear dynamic range of 5.0 × 10−13 to 1.0 × 10−9 M, and the detection limit was determined as 2.2 × 10−13 M using AdDPV under optimized conditions. The results showed that modified electrode has high selectivity and very high sensitivity. The method was used to determine of CFZ in drug injection and plasma samples. © 2018, Institute of Chemistry, Slovak Academy of Sciences.

In this work, a pencil graphite electrode (PGE) was modified using electrochemically reduced graphene oxide (rGO) and then hollow gold nanoparticles (HGNPs) were generated onto rGO/PGE by electrodeposition of cobalt and after that galvanic displacement reaction of cobalt nanoparticles with Au3+ ions. In this way, hollow gold nanoparticles/reduced graphene oxide/pencil graphite electrode (HGNPs/rGO/PGE) was constructed and used for sensitive voltammetric determination of ceftizoxime (CFX). The design experiment as a central composite design (CCD) methodology was developed as the experimental strategy for optimization of the influence of variables on the performance of modified electrode. The modified electrode was characterized using electrochemical impedance spectroscopy (EIS), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and choronocoulometry. The cyclic voltammetry (CV) and adsorptive differential pulse voltammetry (AdDPV) methods were utilized to survey the electrochemical action of CFX on the modified electrode. The linear dynamic range was 1.0×10-12M to 1.0×10-11M and 1.0×10-11M to 1.0×10-9M with a detection limit of 3.5 × 10−13 M. The existent method was employed to the determination of CFX in pharmaceutical and biological samples. © 2018 King Saud University

Aim and Objective: Human dihydroorotate dehydrogenase (DHODH) catalyzes the fourth stage of the biosynthesis of pyrimidines in cells. Hence it is important to identify suitable inhibitors of DHODH to prevent virus replication. In this study, a quantitative structure-activity relationship was performed to predict the activity of one group of newly synthesized halogenated pyrimidine derivatives as inhibitors of DHODH. Materials and Methods: Molecular structures of halogenated pyrimidine derivatives were drawn in the HyperChem and then molecular descriptors were calculated by DRAGON software. Finally, the most effective descriptors for 32 halogenated pyrimidine derivatives were selected using bee algorithm. Results: The selected descriptors using bee algorithm were applied for modeling. The mean relative error and correlation coefficient were obtained as 2.86% and 0.9627, respectively, while these amounts for the leave one out−cross validation method were calculated as 4.18% and 0.9297, respectively. The external validation was also conducted using two training and test sets. The correlation coefficients for the training and test sets were obtained as 0.9596 and 0.9185, respectively. Conclusion: The results of modeling of present work showed that bee algorithm has good performance for variable selection in QSAR studies and its results were better than the constructed model with the selected descriptors using the genetic algorithm method. © 2018 Bentham Science Publishers.