Publications by authors named "Jung Won Keum"

PCR has been a reliable and inexpensive method for nucleic acid detection in the past several decades. In particular, multiplex PCR is a powerful tool to analyze many biomarkers in the same reaction, thus maximizing detection sensitivity and reducing sample usage. However, balancing the amplification kinetics between amplicons and distinguishing them can be challenging, diminishing the broad adoption of high order multiplex PCR panels.

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Non-Watson-Crick base pairing provides an in situ approach for actuation of DNA nanostructures through responses to solution conditions. Here we demonstrate this concept by using physiologically-relevant changes in pH to regulate DNA pyramid assembly/disassembly and to control the release of protein cargo.

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Defects are known to underlie the mechanical properties of materials, especially so at the nanoscale. Using four compositionally identical DNA triangles, defect density is found to be inversely correlated with assembly efficiency and melting temperature. These findings are supported by a series of experiments with more complex DNA pyramids.

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While access to soluble recombinant proteins is essential for a number of proteome studies, preparation of purified functional proteins is often limited by the protein solubility. In this study, potent solubility-enhancing fusion partners were screened from the repertoire of endogenous E. coli proteins.

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Discrete DNA nanostructures allow simultaneous features not possible with traditional DNA forms: encapsulation of cargo, display of multiple ligands, and resistance to enzymatic digestion. These properties suggested using DNA nanostructures as a delivery platform. Here, DNA pyramids displaying antisense motifs are shown to be able to specifically degrade mRNA and inhibit protein expression in vitro, and they show improved cell uptake and gene silencing when compared to linear DNA.

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The ability of both viruses and DNA to self-assemble in solution has continues to enable numerous applications at the nanoscale. Here we review the relevant interactions dictating the assembly of these structures, as well as discussing how they can be exploited experimentally. Because self-assembly is a process, we discuss various strategies for achieving spatial and temporal control.

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The ability of nucleases to perform their catalytic functions depends on the sequence and structural features of target DNA substrates. Due to their size and shape, several DNA tetrahedra are resistant to the action of specific and non-specific nucleases. Such enhanced stability is a key requirement for DNA nanostructures to be useful as delivery vehicles.

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Herein we describe the methods for selective and reversible regulation of gene expression using antisense oligodeoxynucleotides (ODNs) in a cell-free protein synthesis system programmed with multiple DNAs. Either a complete shut down or controlled level of gene expression was attained through the antisense ODN-mediated regulation of mRNA stability in the reaction mixture. In addition to the primary control of gene expression, we also demonstrate that the inhibition of protein synthesis can be reversed by using an anti-antisense ODN sequence that strips the antisense ODN off the target sequence of mRNA.

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We describe a high-throughput strategy for tuning the expression of recombinant proteins through engineering their early nucleotide sequences. After randomizing the +2 and +3 codons of the target genes, each of the variant genes was isolated in vivo and subsequently expressed using in vitro protein synthesis techniques. When several hundreds of clones were examined in parallel, it was found that expression levels of target genes varied as much as 70-fold depending on the identity of the codons in the randomized region.

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In this study, we describe the development of a cost effective and highly productive cell-free protein synthesis system derived from Escherichia coli. Through the use of an optimal energy source and cell extract, approximately 1.3mg/mL of protein was generated from a single batch reaction at greatly reduced reagent costs.

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The accumulation of inorganic phosphate inhibits protein synthesis in cell-free protein synthesis reactions that are energized by high-energy-phosphate-containing compounds. This study developed a new scheme for supplying energy using dual energy sources to enhance the regeneration of ATP and lower the rate of phosphate accumulation. In the proposed scheme, where creatine phosphate (CP) and glucose were simultaneously used as the energy sources, the phosphate released from the CP was subsequently used in the glycolytic pathway for the utilization of the glucose, which enhanced the ATP supply and reduced the rate of inorganic phosphate accumulation.

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In our experiments to produce different combinations of recombinant proteins in a cell-free protein synthesis system derived from Escherichia coli, we found that certain pairs of ORFs were not expressed equally. Instead, only a single DNA species was expressed dominantly, while the expression of the others was almost completely repressed. This bias during the co-expression of the DNA pairs was eliminated when an identical downstream box sequence was added to the 5'-ends of the template DNA pairs.

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In this study, as a part of our efforts to improve the robustness and economical feasibility of cell-free protein synthesis, we developed a simple method of preparing the cell extracts used for catalyzing cell-free protein synthesis reactions. We found that the high-speed centrifugation, pre-incubation, and dialysis steps of the conventional procedures could be omitted without losing the translational activity of the resulting cell extract. Instead, a simple centrifugation step at low speed (12,000 RCF for 10 min) followed by a brief period of incubation was sufficient for the preparation of an active extract to support cell-free protein synthesis with higher productivity and consistency.

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