Hybridization detection of enzyme-labeled DNA at electrically heated electrodes

In this report we describe an electrochemical DNA hybridization sensor approach, in which signal amplification is achieved using heated electrodes together with an enzyme as DNA-label. On the surface of the heatable low temperature co-fired ceramic (LTCC) gold electrode, an immobilized thiolated capture probe was hybridized with a biotinylated target using alkaline phosphatase (SA-ALP) as reporter molecule. The enzyme label converted the redox-inactive substrate 1-naphthyl phosphate (NAP) into the redox-active 1-naphthol voltammetrically determined at the modified gold LTCC electrode. During the measurement only the electrode was heated leaving the bulk solution at ambient temperature. Elevated temperature during detection led to increased enzyme activity and enhanced analytical signals for DNA hybridization detection. The limit of detection at 53 °C electrode temperature was 1.2 nmol/L.     

Preparative isolation of (+)-beta-eudesmol fromAmyris balsamifera

Summary Optically pure (+)-beta-eudesmol is a possible starting material for the synthesis of several termite defense compounds. A two step procedure for the isolation of gram quantities of (+)-beta-eudesmol from commercially availableAmyris balsamifera oil (syn. West Indian sandalwood oil), containing 8% beta-eudesmol, was developed. Step one consisted of an efficient vacuum distillation of the total oil. Step two was a medium pressure LC separation with an AgNO₃ impregnated silica gel stationary phase. Several other separation procedures failed due to the presence of many closely related sesquiterpene alcohols (75% of the oil).     

Reduction of spectra to parameters of an effective Hamiltonian containing the generalized potential energy function: ground state of ArH+

Vibrational-rotational and pure rotational spectra belonging to six isotopomers of ArH+ in the ground electronic state (in total 350 transitions spanning more than half of the potential well depth) were reduced to the parameters of an effective Hamiltonian containing the generalized potential-energy function and the adiabatic and nonadiabatic corrections. The dimensionless standard error of the fit is 0.948. The obtained Hamiltonian is most accurate presently available.     

Cobalt Single-Atom Catalysts with High Stability for Selective Dehydrogenation of Formic Acid

Metal–organic framework (MOF)-derived Co-N-C catalysts with isolated single cobalt atoms have been synthesized and compared with cobalt nanoparticles for formic acid dehydrogenation. The atomically dispersed Co-N-C catalyst achieves superior activity, better acid resistance, and improved long-term stability compared with nanoparticles synthesized by a similar route. High-angle annular dark-field–scanning transmission electron microscopy, X-ray photoelectron spectroscopy, electron paramagnetic resonance, and X-ray absorption fine structure characterizations reveal the formation of Co^IIN_x centers as active sites. The optimal low-cost catalyst is a promising candidate for liquid H₂ generation.     

The radial Hamiltonian for the ground electronic state of KrH+.

All literature vibration-rotational and pure rotational transitions belonging to ten isotopomers of KrH+ in the X'sigma+ state (in total 351 lines) have been used in a iterative nonlinear least-squares fit of compact analytic Born-Oppenheimer potential in the form of generalized potential energy function (GPEF). Additional functions describing the adiabatic and nonadiabatic corrections have also been determined. The obtained radial Hamiltonian reproduces the spectra with sufficiently good accuracy. The GPEF of KrH+ reproduces the experimental value of the dissociation energy, has a correct R(-4) asymptotic behaviour, and reproduces long-range inverse-power potential coefficient C4.     

Direct electrochemistry of horseradish peroxidase immobilized in a chitosan-[C4mim][BF4] film: determination of electrode kinetic parameters

The direct electrochemistry of a HRP-chi-[C(4)mim][BF(4)] film (where HRP = horseradish peroxidase, chi = chitosan, and [C(4)mim][BF(4)] = the room temperature ionic liquid (RTIL) 1-butyl-3-methylimidazolium tetrafluoroborate) has been studied by cyclic voltammetry on a glassy carbon electrode. The mechanism for the electrochemical reaction of HRP is suggested to be EC for the reduction, and CE for the following re-oxidation, as the oxidative peak potential remained approximately unchanged across the scan rate range. The half wave potential of HRP reduction was found to be pH dependent, suggesting that a concomitant proton and electron transfer is occurring. Using theoretical simulations of the experimentally obtained peak positions, the standard electron transfer rate constant, k(0), was found to be 98 (+/-16) s(-1) at 295 K in pH 7 phosphate buffer solution, which is very close to the value reported in the absence of ionic liquid. This suggests that the ionic liquid used here in the HRP-chi-[C(4)mim][BF(4)]/GC electrode does not enhance the rate of electron transfer. k(0) was found to increase systematically with increasing temperature and followed a linear Arrhenius relation, giving an activation energy of 14.20 kJ mol(-1). The electrode kinetics and activation energies obtained are identical to those reported for HRP films in aqueous media. This leads us to question if the use of RTIL films provide any unique benefits for enzyme/protein voltammetry. Rather the films may likely contain aqueous zones in which the enzymes are located and undergo electron transfer.