Publications by authors named "Yong-Chan Kwon"

The development of a robust and cost-effective sensing platform for microRNA (miRNA) is of paramount importance in detecting and monitoring various diseases. Current miRNA detection methods are marred by low accuracy, high cost, and instability. The toehold switch riboregulator has shown promising results in detecting viral RNAs integrated with the freeze-dried cell-free system (CFS).

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The cell-free system offers potential advantages in biosensor applications, but its limited time for protein synthesis poses a challenge in creating enough fluorescent signals to detect low limits of the analyte while providing a robust sensing module at the beginning. In this study, we harnessed split versions of fluorescent proteins, particularly split superfolder green fluorescent protein and mNeonGreen, to increase the number of reporter units made before the reaction ceased and enhance the detection limit in the cell-free system. A comparative analysis of the expression of 1-10 and 11th segments of beta strands in both whole-cell and cell-free platforms revealed distinct fluorescence patterns.

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Cell-free protein synthesis-based biosensors have been developed as highly accurate, low-cost biosensors. However, since most biomarkers exist at low concentrations in various types of biopsies, the biosensor's dynamic range must be increased in the system to achieve low limits of detection necessary while deciphering from higher background signals. Many attempts to increase the dynamic range have relied on amplifying the input signal from the analyte, which can lead to complications of false positives.

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The aim of this work was to evaluate the effects of application time of an acid mixture solution on the surface roughness, phase transformation, and biaxial flexural strength of 3Y-TZP after sintering or air abrasion. For the biaxial flexural strength measurement, 220 3Y-TZP disk-shaped specimens were prepared after as-sintering or air abrasion. The etching solution comprised a mixture of hydrofluoric acid, sulfuric acid, hydrogen peroxide, methyl alcohol, and purified water.

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The modern cell-free protein synthesis (CFPS) system is expanding the opportunity of cell-free biomanufacturing as a versatile platform for synthesizing various therapeutic proteins. However, synthesizing human protein in the bacterial CFPS system remains challenging due to the low expression level, protein misfolding, inactivity, and more. These challenges limit the use of a bacterial CFPS system for human therapeutic protein synthesis.

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Detoxifying effects of hyperoxia, which is widely used in clinical practice, were investigated using HaCat cells (human keratinocytes) treated with benzo[a]pyrene (B[a]P) as a model agent to induce adverse effects in the skin. It is well-established that B[a]P may produce toxicities including cancer, endocrine disruption, and phototoxicity involving DNA damage, free radical generation, and down regulation of nuclear factor erythroid 2-related factor 2 (Nrf2). It is well-known that Nrf2 is associated increase of antioxidant enzyme catalase (CAT) or detoxification enzyme glutathione S-transferase (GST) in HaCat cells treated with B[a]P under optimal condition of hyperoxia (40% oxygenation) conditions.

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We describe a device engineered for realistic simulation of myringotomy and tympanostomy tube insertion that tracks instrument placement and objectively measures operator proficiency. A 3-dimensional computer model of the external ear and cartilaginous external auditory canal was created from a normal maxillofacial computed tomography scan, and models for the bony external auditory canal and tympanic cavity were created with computer-aided design software. Physical models were 3-dimensionally printed from the computer reconstructions.

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With the advancement of synthetic biology, the cell-free protein synthesis (CFPS) system has been receiving the spotlight as a versatile toolkit for engineering natural and unnatural biological systems. The CFPS system reassembles the materials necessary for transcription and translation and recreates the in vitro protein synthesis environment by escaping a physical living boundary. The cell extract plays an essential role in this in vitro format.

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The mixture of 5-chloro-2-methylisothiazol-3(2H)-one (CMIT) and 2-methylisothiazol-3(2H)-one (MIT), CMIT/MIT, is a preservative in cosmetics. CMIT/MIT is a highly effective preservative; however, it is also a commonly known skin sensitizer. Therefore, in the present study, a risk assessment for safety management of CMIT/MIT was conducted on products containing 0.

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Colicins are antimicrobial proteins produced by , which, upon secretion from the host, kill non-host strains by forming pores in the inner membrane and degrading internal cellular components such as DNA and RNA. Due to their unique cell-killing activities, colicins are considered viable alternatives to conventional antibiotics. Recombinant production of colicins requires co-production of immunity proteins to protect host cells; otherwise, the colicins are lethal to the host.

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N-nitrosamines and their precursors found in cosmetics may be carcinogenic in humans. Thus the aim of this study was to carry out risk assessment for N-nitrosamines (N-nitrosodiethanolamine [NDELA], N-nitrosodiethylamine [NDEA]) and amines (triethanolamine [TEA], diethanolamine [DEA]) levels in cosmetics determined using validated liquid chromatography-tandem mass spectrometry (LC-MS/MS) procedures. NDELA and NDEA concentrations were present at levels of "not detected" (N.

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The heavy metal content of cosmetics may be a cause for concern in that exposure to these metals is associated with adverse consequences. Thus, the aim of this study was to assess consequences attributed to exposure to heavy metals in cosmetics as determined by non-cancer, cancer, and sensitization risks methodologies. The quantification and exposure assessments of aluminum (Al), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As), lead (Pb), mercury (Hg), cadmium (Cd), antimony (Sb), and titanium (Ti) were performed by inductively coupled plasma-mass spectrometry.

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Cell-free protein synthesis has emerged as a powerful approach for expanding the range of genetically encoded chemistry into proteins. Unfortunately, efforts to site-specifically incorporate multiple non-canonical amino acids into proteins using crude extract-based cell-free systems have been limited by release factor 1 competition. Here we address this limitation by establishing a bacterial cell-free protein synthesis platform based on genomically recoded Escherichia coli lacking release factor 1.

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Centralized facilities for genetic engineering, or "biofoundries", offer the potential to design organisms to address emerging needs in medicine, agriculture, industry, and defense. The field has seen rapid advances in technology, but it is difficult to gauge current capabilities or identify gaps across projects. To this end, our foundry was assessed via a timed "pressure test", in which 3 months were given to build organisms to produce 10 molecules unknown to us in advance.

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N-nitrosodiethanolamine (NDELA), a type of nitrosamine, is a possible human carcinogen that may form in cosmetic products. The aim of this study was to examine the formation and inhibition of NDELA through chemical reactions of secondary amines including mono-ethanolamine, di-ethanolamine (DEA), and tri-ethanolamine (TEA), and sodium nitrite (SN) under varying conditions such as pH, temperature, and fluorescent, ultraviolet (UV), and visual light (VIS) using liquid chromatography-mass spectroscopy. In a mixture of TEA and SN under acidic conditions pH 2, residual NDELA concentrations rose significantly under various storage conditions in the following order: 50°C > 40°C > UV (2 W/m) > VIS (4000 lux) > fluorescent light > 25°C > 10°C.

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Cell-free protein synthesis (CFPS) has emerged as a powerful platform for applied biotechnology and synthetic biology, with a range of applications in synthesizing proteins, evolving proteins, and prototyping genetic circuits. To expand the current CFPS repertoire, we report here the development and optimization of a Streptomyces-based CFPS system for the expression of GC-rich genes. By developing a streamlined crude extract preparation protocol and optimizing reaction conditions, we were able to achieve active enhanced green fluorescent protein (EGFP) yields of greater than 50 μg/mL with batch reactions lasting up to 3 h.

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Site-specific incorporation of non-standard amino acids (NSAAs) into proteins opens the way to novel biological insights and applications in biotechnology. Here, we describe the development of a high yielding cell-free protein synthesis (CFPS) platform for NSAA incorporation from crude extracts of genomically recoded Escherichia coli lacking release factor 1. We used genome engineering to construct synthetic organisms that, upon cell lysis, lead to improved extract performance.

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Crude extract based cell-free protein synthesis (CFPS) has emerged as a powerful technology platform for high-throughput protein production and genetic part characterization. Unfortunately, robust preparation of highly active extracts generally requires specialized and costly equipment and can be labor and time intensive. Moreover, cell lysis procedures can be hard to standardize, leading to different extract performance across laboratories.

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Incorporating non-standard amino acids (NSAAs) into proteins enables new chemical properties, new structures, and new functions. In recent years, improvements in cell-free protein synthesis (CFPS) systems have opened the way to accurate and efficient incorporation of NSAAs into proteins. The driving force behind this development has been three-fold.

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We present a strategy for expression and screening of microbial enzymes without involving cloning procedures. Libraries of putative ω-transaminases (ω-TA) and mutated Candida antarctica lipase B (CalB) are PCR-amplified from bacterial colonies and directly expressed in an Escherichia coli-based cell-free protein synthesis system. The open nature of cell-free protein synthesis system also allows streamlined analysis of the enzymatic activity of the expressed enzymes, which greatly shortens the time required for enzyme screening.

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Harnessing the isolated protein synthesis machinery, cell-free protein synthesis reproduces the cellular process of decoding genetic information in artificially controlled environments. More often than not, however, generation of functional proteins requires more than simple translation of genetic sequences. For instance, many of the industrially important enzymes require non-protein prosthetic groups for biological activity.

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Cytochrome P450 monooxygenases are multifunctional enzymes with potential applications in chemoenzymatic synthesis of complex chemicals as well as in studies of metabolism and xenobiotics. Widespread application of cytochrome P450s, however, is encumbered by the critical need for redox equivalents in their catalytic function. To overcome this limitation, we studied visible light-driven regeneration of NADPH for P450-catalyzed O-dealkylation reaction; we used eosin Y as a photosensitizing dye, triethanolamine as an electron donor, and [Cp*Rh(bpy)H₂O] as an electron mediator.

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Herewith we report the expression and screening of microbial enzymes without involving cloning procedures. Computationally predicted putative omega-transaminase (omega-TA) genes were PCR amplified from the bacterial colonies and expressed in a cell-free protein synthesis system for subsequent analysis of their enzymatic activity and substrate specificity. Through the cell-free expression analysis of the putative omega-TA genes, a number of enzyme-substrate pairs were identified in a matter of hours.

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Although the cell-free translation system is now widely accepted as an efficient platform for production, engineering and screening of recombinant proteins, it has not been successfully used for the synthesis of peptide molecules mainly due to low expression yields and rapid proteolysis of the expressed peptides. In this study, we propose a novel strategy for rapid expression and recovery of peptide molecules which involves the rational design of template DNA and heterogenous cell-free translation reaction in the presence of affinity beads. Various peptide molecules which were not expressed in a detectable level were successfully expressed and recovered in situ in a substantial yield.

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