Joon Young Lee

Simple and Universal Platform for Logic Gate Operations Based on Molecular Beacon Probes

A new platform technology is herein described with which to construct molecular logic gates by employing the hairpin-structured molecular beacon probe as a basic work unit. In this logic gate operation system, single-stranded DNA is used as the input to induce a conformational change in a molecular beacon probe through a sequence-specific interaction. The fluorescent signal resulting from the opening of the molecular beacon probe is then used as the output readout. Importantly, because the logic gates are based on DNA, thus permitting input/output homogeneity to be preserved, their wiring into multi-level circuits can be achieved by combining separately operated logic gates or by designing the DNA output of one gate as the input to the other. With this novel strategy, a complete set of two-input logic gates is successfully constructed at the molecular level, including OR, AND, XOR, INHIBIT, NOR, NAND, XNOR, and IMPLICATION. The logic gates developed herein can be reversibly operated to perform the set-reset function by applying an additional input or a removal strand. Together, these results introduce a new platform technology for logic gate operation that enables the higher-order circuits required for complex communication between various computational elements.

Generating Fluttering Patterns with Low Autocorrelation for Coded Exposure Imaging

The performance of coded exposure imaging critically depends on finding good binary sequences. Previous coded exposure imaging methods have mostly relied on random searching to find the binary codes, but that approach can easily fail to find good long sequences, due to the exponentially expanding search space. In this paper, we present two algorithms for generating the binary sequences, which are especially well suited for generating short and long binary sequences, respectively. We show that the concept of low autocorrelation binary sequences, which has been successfully exploited in the field of information theory, can be applied to generate shutter fluttering patterns. We also propose a new measure for good binary sequences. Based on the new measure, we introduce two new algorithms for coded exposure imaging - a modified Legendre sequence method and a memetic algorithm. Experiments using both synthetic and real data show that our new algorithms consistently generate better binary sequences for the coded exposure problem, yielding better deblurring and resolution enhancement results compared to previous methods of generating the binary codes.

An impedimetric determination of alkaline phosphatase activity based on the oxidation reaction mediated by Cu2+ bound to poly-thymine DNA

We herein describe a novel impedimetric method to determine alkaline phosphatase (ALP) activity based on the Cu2+-mediated oxidation of ascorbic acid on a specific DNA probe-modified electrode. In this method, pyrophosphate (PPi) capable of complexing with Cu2+ is employed as a substrate of the ALP enzyme. In the presence of ALP, PPi is hydrolyzed to phosphate (Pi), which is not able to entrap Cu2+. The free Cu2+ are specifically bound to a poly-thymine DNA probe immobilized on the electrode surface and reduced to form copper nanoparticles by a concomitant oxidation of ascorbic acid. As a result, the oxidation products of ascorbic acid are accumulated on the electrode surface, which consequently increase electron transfer resistance (Ret) by interrupting the electron transfer on the electrode. On the other hand, in the absence of ALP, PPi remains intact to effectively capture Cu2+, consequently preventing the oxidation of ascorbic acid and the subsequent increase of Ret. Based on this design principle, the change in Ret, which is proportional to ALP activity, was measured by electrochemical impedance spectroscopy (EIS) and ALP activities were successfully determined down to 6.5 pM (7.2 U L−1) with excellent selectivity.

Label-Free Multiplex DNA Detection Utilizing Projected Capacitive Touchscreen

A novel strategy to achieve label-free multiplex DNA detection system based on the projected capacitive touchscreen is developed. Touchscreen panel is first fabricated by patterning the ITO (indium-tin-oxide) electrode array on the glass wafer, and the electrodes are modified with the respective capture probe DNA sequences complementary to hemagglutinin1 (H1), neuraminidase1 (N1), and matrix1 (M1) DNA to demonstrate the molecular diagnosis of H1N1 influenza virus as a model pathogen. DNA sample is applied to the electrodes to allow hybridization of target DNA with the corresponding complementary capture probe. As a result, the hybridization event significantly enhanced the capacitance on the electrode, which can be very conveniently detected by the projected capacitive touchscreen. Based on this design principle, the authors have successfully detected target regions of H1N1 influenza virus in a label-free multiplexed manner. This touchscreen-based detecting system would greatly benefit the point-of-care testing (POCT) in various diagnostic applications.