Electrochemical genosensors for the detection of Bonamia parasite. Selection of single strand-DNA (ssDNA) probes by simulation of the secondary structure folding

A post-PCR nucleic acid work by comparing experimental data, from electrochemical genosensors, and bioinformatics data, derived from the simulation of the secondary structure folding and prediction of hybridisation reaction, was carried out in order to rationalize the selection of ssDNA probes for the detection of two Bonamia species, B. exitiosa and B. ostreae, parasites of Ostrea edulis.Six ssDNA probes (from 11 to 25 bases in length, 2 thiolated and 4 biotinylated) were selected within different regions of B. ostreae and B. exitiosa PCR amplicons (300 and 304 bases, respectively) with the aim to discriminate between these parasite species. ssDNA amplicons and probes were analyzed separately using the “Mfold Web Server” simulating the secondary structure folding behaviour. The hybridisation of amplicon-probe was predicted by means of “Dinamelt Web Server”. The results were evaluated considering the number of hydrogen bonds broken and formed in the simulated folding and hybridisation process, variance in gaps for each sequence and number of available bases. In the experimental part, thermally denatured PCR products were captured at the sensor interface via sandwich hybridisation with surface-tethered probes (thiolated probes) and biotinylated signalling probes. A convergence between analytical signals and simulated results was observed, indicating the possibility to use bioinformatic data for ssDNA probes selection to be incorporated in genosensors.     

Accelerating and decelerating effects of metal ions on electron-transfer reduction of quinones as a function of temperature and binding modes of metal ions to semiquinone radical anions

The accelerating effect of Sc(3+) on the electron-transfer (ET) reduction of the p-benzoquinone derivative 1-(p-tolylsulfinyl)-2,5-benzoquinone (TolSQ) by 10,10'-dimethyl-9,9'-biacridine ((AcrH)(2)) at 233 K changes to a decelerating effect with increasing reaction temperature; the observed second-order rate constant k(et) decreases with increasing Sc(3+) concentration at high concentrations of Sc(3+) at 298 K. At 263 K the k(et) value remains constant with increasing Sc(3+) concentration. Such a remarkable difference with regard to dependence of k(et) on [Sc(3+)] between low and high temperatures results from the difference in relative activity of two ET pathways that depend on temperature, one of which affords 1:1 complex TolSQ*(-)-Sc(3+), and the other 1:2 complex TolSQ*(-)-(Sc(3+))(2) with additional binding of Sc(3+) to TolSQ*(-)-Sc(3+). The formation of TolSQ*(-)-Sc(3+) and TolSQ*(-)-(Sc(3+))(2) complexes was confirmed by EPR spectroscopy in the ET reduction of TolSQ in the presence of low and high concentrations of Sc(3+), respectively. The effects of metal ions on other ET reactions of quinones to afford 1:1 and 1:2 complexes between semiquinone radical anions and metal ions are also reported. The ET pathway affording the 1:2 complexes has smaller activation enthalpies DeltaH( not equal) and more negative activation entropies DeltaS( not equal) because of stronger binding of metal ions and more restricted geometries of the ET transition states as compared with the ET pathway to afford the 1:1 complexes.     

Gamow-teller strengths of the inverse beta transition 176Yb-->176Lu for spectroscopy of proton-proton and other sub-MeV solar neutrinos

Discrete Gamow-Teller (GT) transitions 176Yb-->176Lu at low excitation energies have been measured via the ( 3He,t) reaction at 450 MeV and at 0 degrees. For 176Yb, two low-lying states are observed, setting low thresholds Q(nu) = 301 and 445 keV for neutrino ( nu) capture. Capture rates estimated from the measured GT strengths, the simple two-state excitation structure, and the low Q(nu) in Yb-Lu indicate that Yb-based nu detectors are well suited for a direct measurement of the sub-MeV solar electron-neutrino ( nu(e)) spectrum including pp neutrinos.     

Three dimensional gain analysis of free electron laser with focusing permanent magnet wiggler

A three dimensional simulation software system developed to estimate a free electron laser (FEL) gain has been applied to FEL using a standard plane polarized wiggler and an alternately shifted magnet wiggler. It is seen for the latter wiggler that a large filling factor could be selected and each maximum gain corresponding to each orbit of electron beam concentrates at a certain frequency region of FEL radiation. It is, therefore, implied that a proper shift between the adjacent magnets in the wiggler produces the improvement of the FEL gain.     

Superthermostability of nanoscale TIC-reinforced copper alloys manufactured by a two-step ball-milling process

A Cu-TiC alloy, with nanoscale TiC particles highly dispersed in the submicron-grained Cu matrix, was manufactured by a self-developed two-step ball-milling process on Cu, Ti and C powders. The thermostability of the composite was evaluated by high-temperature isothermal annealing treatments, with temperatures ranging from 727 to 1273 K. The semicoherent nanoscale TiC particles with Cu matrix, mainly located along the grain boundaries, were found to exhibit the promising trait of blocking grain boundary migrations, which leads to a super-stabilized microstructures up to approximately the melting point of copper (1223 K). Furthermore, the Cu-TiC alloys after annealing at 1323 K showed a slight decrease in Vickers hardness as well as the duplex microstructure due to selective grain growth, which were discussed in terms of hardness contributions from various mechanisms.     

Hybrid Planar Wiggler with a Period of 2 cm for Higher Harmonic FEL Lasing

A hybrid planar wiggler with a period of 20 mm has been studied as the simplest one which gives the strong field including some higher harmonic components by selecting proper sizes of the ferromagnetic and the permanent magnet. Small gap length of the wiggler and small width of permendur satisfy these conditions to a certain degree.Gain analysis of FEL suggests that for high wiggler field of K>1 1.6, higher harmonic gains are improved primarily due to its strong field, and for low wiggler field of K< 1 1.6, they are mainly due to the modification of the wiggler field distribution.