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We demonstrate nanogap biosensors for electrical and label-free detection of biomolecular interactions. Parallel fabrication of nanometer distance gaps has been achieved using a silicon anisotropic wet etching technique on a silicon-on-insulator (SOI) wafer with a finely controllable silicon device layer. Since silicon anisotropic wet etching resulted in a trapezoid-shaped structure whose end became narrower during the etching, the nanogap structure was simply fabricated on the device layer of a SOI wafer. The nanogap devices were individually addressable and a gap size of less than 60 nm was obtained. We demonstrate that the nanogap biosensors can electrically detect biomolecular interactions such as biotin/streptavidin and antigen/antibody pairs. The nanogap devices show a current increase when the proteins are bound to the surface. The current increases proportionally depending upon the concentrations of the molecules in the range of 100 fg ml(-1)-100 ng ml(-1) at 1 V bias. It is expected that the nanogap developed here could be a highly sensitive biosensor platform for label-free detection of biomolecular interactions.

This article examines interdependence between oil price shocks and UnitedStates economic uncertainty and their effects on global stock markets within a structural VAR model over the last 40 years. I find that aggregate demand shocks cause a transitory rise in global real stock returns, whereas precautionary oil demand and United States economic uncertainty shocks decline the returns. Especially, oil demand shocks significantly increase United States economic uncertainty, indicating that their direct impacts on global stock markets are amplified by its endogenous response. Variance decomposition analysis shows that oil price shocks and United States economic uncertainty explain 17% and 6% of long-run variations in global real stock returns, respectively. These figures have more than tripled when the model is estimated on post 2000 data, suggesting that oil market fundamentals and United States macro uncertainty are an important determinant of global stock market movements.

We report the new method for detection of DNA hybridization using enzymatic cleavage. The strategy is based on that S1 nuclease is able to specifically cleave only single strand DNA, but not double strand DNA. The capture probe DNA, thiolated single strand DNA labeled with electroactive ferrocene group, was immobilized on a gold electrode. After hybridization of target DNA of complementary and noncomplementary sequences, nonhybridized single strand DNA was cleaved using S1 nuclease. The difference of enzymatic cleavage on the modified gold electrode was characterized by cyclic voltammetry and differential pulse voltammetry. We successfully applied this method to the sequence-selective discrimination between perfectly matched and mismatched target DNA including a single-base mismatched target DNA. Our method does not require either hybridization indicators or other exogenous signaling molecules which most of the electrochemical hybridization detection systems require.

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