Search

This work reports new analytical applications of glassy carbon electrodes (GCE) modified with a nanohybrid obtained by non-covalent functionalization of multi-walled carbon nanotubes (MWCNTs) with human immunoglobulin G (IgG) (GCE/MWCNT-IgG). We report the label-free and non-amplified breast cancer 1 gen (BRCA1) biosensing based on the facilitated adsorption of the DNA probe at the nanohybrid modified GCE and the impedimetric detection of the hybridization event in the presence of the redox marker benzoquinone/hydroquinone. The resulting genosensor made the fast, highly selective, and sensitive quantification of BRCA1 gene possible, with a linear range between 1.0 fM and 10.0 nM, a sensitivity of (3.0 ± 0.1) × 102 Ω M−1 (R2 = 0.9990), a detection limit of 0.3 fM, and excellent discrimination of fully non-complementary and mismatch DNA sequences. The detection of BRCA1 in enriched samples of diluted human blood serum showed a recovery percentage of 94.6%. Another interesting analytical application of MWCNT-IgG-modified GCE based on the catalytic activity of the exfoliated MWCNTs is also reported for the simultaneous quantification of dopamine and uric acid in the presence of ascorbic acid, with detection limits at submicromolar levels for both compounds. [ABSTRACT FROM AUTHOR]

Rate coefficients for the gas-phase reactions of OH radicals with a series of unsaturated alcohols are measured. Results obtained are presented in terms of the influence of the OH group on the reactivity of the alcohols.

Currently, the biosynthesis of silver-based nanomaterials attracts enormous attention owing to the documented antimicrobial properties of these ones. This study reports the extracellular biosynthesis of silver nanoparticles (Ag-NPs) using a Pseudomonas aeruginosa strain from a reference culture collection. A greenish culture supernatant of P. aeruginosa incubated at 37°C with a silver nitrate solution for 24 h changed to a yellowish brown color, indicating the formation of Ag-NPs, which was confirmed by UV-vis spectroscopy, transmission electron microscopy, and X-ray diffraction. TEM analysis showed spherical and pseudospherical nanoparticles with a distributed size mainly between 25 and 45 nm, and the XRD pattern revealed the crystalline nature of Ag-NPs. Also it provides an evaluation of the antimicrobial activity of the biosynthesized Ag-NPs against human pathogenic and opportunistic microorganisms, namely, Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus faecalis, Proteus mirabilis, Acinetobacter baumannii, Escherichia coli, P. aeruginosa, and Klebsiella pneumonia. Ag-NPs were found to be bioactive at picomolar concentration levels showing bactericidal effects against both Gram-positive and Gram-negative bacterial strains. This work demonstrates the first helpful use of biosynthesized Ag-NPs as broad spectrum bactericidal agents for clinical strains of pathogenic multidrug-resistant bacteria such as methicillin-resistant S. aureus, A. baumannii, and E. coli. In addition, these Ag-NPs showed negligible cytotoxic effect in human neutrophils suggesting low toxicity to the host. [ABSTRACT FROM AUTHOR]

Abstract: The relative rate technique has been used to determine the rate constants of the reactions of Cl atoms with 2-chloro-1,1,2-trifluoroethyl-methyl-ether (CH3OCF2CHFCl) and 2-chloro-1,1,2-trifluoroethyl-difluoromethyl-ether (CHF2OCF2CHFCl). Experiments were carried out at 296±2K and atmospheric pressure using nitrogen or synthetic air as bath gases. The decay rates of the organic species were measured relative to those of 1,2-dichloroethane, dichloromethane and 1,1,1,2-tretrafluoroethane. The following rate coefficients were derived for the reaction of Cl atoms (in units of cm3 molecule−1 s−1) with CH3OCF2CHFCl, k=(3.24±0.49)×10−13 and CHF2OCF2CHFCl, k=(3.20±0.32)×10−15. The rate constants obtained are compared with previous literature data to establish reactivity trends and used to estimate the atmospheric lifetimes for the studied ethers. From the calculated lifetimes, using average global concentrations of Cl atoms and OH radicals, the atmospheric loss of CH3OCF2CHFCl and CHF2OCF2CHFCl is determined by the OH-initiated oxidation. The atmospheric implications of these reactions are discussed based on the calculated ozone depletion potential (ODP) and global warming potential (GWP) of the ethers. [Copyright &y& Elsevier]

The temperature dependences of the rate coefficients of the gas-phase reactions of O(3P) atoms with CH2=CHCH2Cl and CH2=CClCH3 were studied in the range 298–359 K, using the discharge flow-chemiluminescence technique. The Arrhenius expressions obtained (in units of cm3 molecule−1 s−1) were: k1 = (1.96 ± 0.33)×10−10exp[(−1476 ± 56)/T] and k2 = (9.11 ± 0.17)×10−11exp[(−1007 ± 61)/T] with Ea in Jmol−1. Theoretical calculations at different levels of theory were carried out. Both, theoretical and experimental results, support the conclusion that addition of O(3P) to the less substituted carbon atom of the double bond of the studied chloropropenes, is the main pathway of the reactions. [Copyright &y& Elsevier]

The relative rate technique has been used to determine the rate constants of the reactions of OH radicals with CF(3)CCl=CCl(2) (k(1)), CF(3)CCl=CClCF(3) (k(2)) and CF(3)CF=CFCF(3) (k(3)). Experiments were carried out at (298±2) K and atmospheric pressure using ultrapure nitrogen as gas bath. The decay rates of the organic species were measured relative to those of ethane, methanol, acetone, chloroethane and 2-butanone. The following rate constants were derived in units of cm(3) molecule(-1) s(-1): k(1)= (10±1)×10(-13), k(2)=(2.1±0.2)×10(-13) and k(3)=(3.7±0.2)×10(-13). This is the first experimental determination of k(1) and k(2). The rate constants obtained are compared with previous literature data to establish reactivity trends and are used to estimate the atmospheric lifetimes of the studied perhaloalkenes. From the calculated lifetimes, using an average global concentration of hydroxyl radicals, the atmospheric loss of these compounds by the OH-initiated oxidation was determined. Also, estimations have been made of the ozone depletion potential (ODP), the radiative forcing efficiency (RE), the halocarbon global warming potential (HGWP) and the global warming potential (GWP) of the perhaloalkenes. The approximate nature of these values is stressed considering that these are short-lived compounds for which these atmospheric parameters may vary according to latitude and season.