Preliminary evaluation of electrochemical PNA array for detection of single base mismatch mutations

We report here a preliminary evaluation of a microfabricated disposable-type peptide nucleic acid (PNA) array, with a 20-channel electrode, for the detection of cancer gene c-Ki-ras. Synthetic 15-mer PNA probes complimentary to ras sequence modified with cysteine were immobilized on the gold electrodes on the array. The electrochemical PNA array was reacted with 20-mer oligonucleotide target or 128 bp PCR product for 1 h. The anodic current derived from an electrochemically active DNA binder Hoechst 33258 was measured using the PNA array in the 50 microL of reaction chamber. The anodic current from Hoechst 33258 increased with increasing the concentration of PCR product of ras gene in the range from 10(11) to 10(15) copy mL(-1). The single base mismatch mutations of c-Ki-ras/61 were also detected using the electrochemical PNA array.     

Zero-magnetization ferromagnet proven by helicity-switching Compton scattering

A single crystal of gadolinium-doped SmAl(2) has zero magnetization in the midst of the ordered temperature region, despite the probable ferromagnetic spin ordering. The asymmetry in Compton-scattering intensity when switching between right- and left-handed polarization of incident 150-keV synchrotron radiation provides decisive proof that ferromagnetic order is really there, and that spin and orbital magnetic contributions cancel. The experiments also show that the spin direction at this zero-magnetization state is rather stable against the external magnetic field and, nevertheless, reversible by a preceding control of temperature and an external field.     

Laser-hole boring into overdense plasmas measured with soft X-Ray laser probing

A laser self-focused channel formation into overdense plasmas was observed using a soft x-ray laser probe system with a grid image refractometry (GIR) technique. 1.053 &mgr;m laser light with a 100 ps pulse duration was focused onto a preformed plasma at an intensity of 2x10(17) W/cm (2). Cross sections of the channel were obtained which show a 30 &mgr;m diameter in overdense plasmas. The channel width in the overdense region was kept narrow as a result of self-focusing. Conically diverging density ridges were also observed along the channel, indicating a Mach cone created by a shock wave due to the supersonic propagation of the channel front.     

Surface structure of In/Si(1 1 1) studied by reflection high-energy positron diffraction

We have investigated a quasi-one-dimensional structure of In/Si(1 1 1) surface using reflection high-energy positron diffraction (RHEPD), which is sensitive to the topmost surface structure under the total reflection condition. From the rocking curves, we found that In atoms are located at two different vertical positions, i.e., 0.99 Å and 0.55 Å from the Si zigzag chain in both 4 × 1 (210 K) and 8 × 2 (60 K) phases.     

Observation of single Ca ions for trace isotope analysis

We developed an ion trap — laser cooling system for observing the laser induced fluorescence (LIF) of a single ion, in the view of utilizing it for the trace isotope analysis of Ca. We observed stepwise LIF signals, which correspond to the numbers of trapped ⁴⁰Ca⁺ ions (⁴⁰Ca/Ca = 96.9%). The detection efficiency was evaluated and the observation of single ions demonstrated the experimental feasibility of trace isotope analysis. Furthermore, as the next step towards trace isotope analysis, we report observation of the even calcium isotopes, ⁴⁴Ca (⁴⁴Ca/Ca = 2.09%) and ⁴⁸Ca (⁴⁸Ca/Ca = 0.187%), without the use of a selective loading method.