Browsing by Author "Su, Yu-Chih"

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Azide-alkyne cycloaddition for universal post-synthetic modifications of nucleic acids and effective synthesis of bioactive nucleic acid conjugates
(2014)
Su, Yu-Chih
;
Lo, Yu-Lun
;
Hwang, Chi-Ching
;
Wang, Li-Fang
;
Wu, Min Hui
The regioselective post-synthetic modifications of nucleic acids are essential to studies of these molecules for science and applications. Here we report a facile universal approach by harnessing versatile phosphoramidation reactions to regioselectively incorporate alkynyl/azido groups into post-synthetic nucleic acids primed with phosphate at the 5\' termini. With and without the presence of copper, the modified nucleic acids were subjected to azide-alkyne cycloaddition to afford various nucleic acid conjugates including a peptide-oligonucleotide conjugate (POC) with high yield. The POC was inoculated with human A549 cells and demonstrated excellent cell-penetrating ability despite cell deformation caused by a small amount of residual copper chelated to the POC. The combination of phosphoramidation and azide-alkyne cycloaddition reactions thus provides a universal regioselective strategy to post-synthetically modify nucleic acids. This study also explicated the toxicity of residual copper in synthesized bioconjugates destined for biological systems.
Effective and site-specific phosphoramidation reaction for universally labeling nucleic acids
(2014-03-15)
Su, Yu-Chih
;
Chen, Hsing-Yin
;
Ko, Ni Chien
;
Hwang, Chi-Ching
;
Wu, Min Hui
Here we report efficient and selective postsynthesis labeling strategies, based on an advanced phosphoramidation reaction, for nucleic acids of either synthetic or enzyme-catalyzed origin. The reactions provided phosphorimidazolide intermediates of DNA or RNA which, whether reacted in one pot (one-step) or purified (two-step), were directly or indirectly phosphoramidated with label molecules. The acquired fluorophore-labeled nucleic acids, prepared from the phosphoramidation reactions, demonstrated labeling efficacy by their F/N ratio values (number of fluorophores per molecule of nucleic acid) of 0.02-1.2 which are comparable or better than conventional postsynthesis fluorescent labeling methods for DNA and RNA. Yet, PCR and UV melting studies of the one-step phosphoramidation-prepared FITC-labeled DNA indicated that the reaction might facilitate nonspecific hybridization in nucleic acids. Intrinsic hybridization specificity of nucleic acids was, however, conserved in the two-step phosphoramidation reaction. The reaction of site-specific labeling nucleic acids at the 5'-end was supported by fluorescence quenching and UV melting studies of fluorophore-labeled DNA. The two-step phosphoramidation-based, effective, and site-specific labeling method has the potential to expedite critical research including visualization, quantification, structural determination, localization, and distribution of nucleic acids in vivo and in vitro. (C) 2013 Elsevier Inc. All rights reserved.
In Vitro Selection and Characterization of a Novel Zn(II)-Dependent Phosphorothiolate Thiolesterase Ribozyme
(2012-01-10)
Wang, Tzu-Pin
;
Su, Yu-Chih
;
Chen, Yi
;
Liou, Yi-Ming
;
Lin, Kun-Liang
Here we present the in vitro selection of a novel ribozyme specific for Zn(2+)-dependent catalysis on hydrolysis of a phosphorothiolate thiolester bond. The ribozyme, called the TW17 ribozyme, was evolved and selected from an artificial RNA pool covalently linked to a biotin-containing substrate through the phosphorothiolate thiolester bond. The secondary structure for the evolved ribozyme consisted of three major helices and three loops. Biochemical and chemical studies of ribozyme-catalyzed reaction products provided evidence that the ribozyme specifically catalyzes hydrolysis of the phosphorothiolate thiolester linkage. A successful ribozyme construct with active catalysis in trans further supported the determined ribozyme structure and indicated the potential of the ribozyme for multiple-substrate turnover. The ribozyme also requires Zn(2+) and Mg(2+) for maximal catalysis. The TW17 ribozyme, in the presence of Zn(2+) and Mg(2+), conferred a rate enhancement of at least S orders of magnitude when compared to the estimated rate of the uncatalyzed reaction. The ribozyme completely lost catalytic activity in the absence of Zn(2+), like Zn(2+)-dependent protein hydrolases. The discovery and characterization of the TW17 ribozyme suggest additional roles for Zn(2+) in ribozyme catalysts.
Photon recycling characteristics of InGaAs/GaAsP multiple quantum well solar cells incorporating a spectrally selective filter and distributed Bragg reflector
(2019-12-09)
Hong, Chung-Yu
;
Wang, Yi-Chin
;
Su, Yu-Chih
;
Tsai, Jia-Ling
;
Tung, Chao-Ming
Photon management plays a vital role in the power conversion efficiency of III-V semiconductor solar cells. However, the photon recycling characteristics of GaAs-based multi-quantum-well (MQW) solar cells employed different optical designs had yet been fully explored. In this work, we investigate the impact of the spectrally selective filter (SSF) and distributed Bragg reflector (DBR) on the photovoltaic characteristics of single-junction, strain-balanced In0.1Ga0.9As/ GaAs0.85P0.15 MQW solar cells. Specifically, the SSFs with cutoff wavelengths of 880, 910, and 940 nm are designed and implemented on MQW solar cells with and without the incorporation of a rear DBR. Photon confinement in the vertical direction is verified based on the characterizations of reflectance, electroluminescence, and external quantum efficiency. We show that the photon confinement reduces the saturation current density, up to 26 times and 3 times for the 880 nm SSF-MQW and SSF-MQW-DBR devices, respectively, compared to that of the 940 nm devices. Furthermore, by comparing the SSF-MQW-DBR solar cells under simulated one-sun and concentrated illumination conditions, the open-circuit voltage exhibits a maximal net increase for the 910 nm SSF due to tradeoff between the short-circuit and saturation current density. The proposed SSF design may offer a viable approach to boost the performance of GaAs-based MQW solar cells. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
Photovoltaic Characteristics of Multiple Quantum Well Solar Cells with Distributed Bragg Reflector and Selective Filters
(2016-01-01)
Hong, Chung-Yu
;
Wang, Yi-Chin
;
Hung, Mu-Min
;
Su, Yu-Chih
;
Tsai, Jia-Ling
We investigate the photon recycling characteristics of single junction solar cells incorporating 50-pairs multiple quantum wells (MQW) to exploit the high radiative recombination rate in one-dimensional carrier-confinement structures. In particular, we systematically compare solar cells with monolithically grown distributed Bragg reflectors (DBRs), as well as selective filters (SFs) with cutoff wavelengths of 880, 910, and 930 nm under standard and concentrated illumination conditions. Optical confinement in the vertical direction is verified based on the reflective spectra and electroluminescence properties. Consequently, the photo-recycling effect manifests under concentrated conditions, where the maximal open circuit voltage difference, by 12mV under 200x illumination, is achieved for MQW solar cells incorporating both the DBR and the 910-nm-cutoff SF, compared to those without the DBR or SFs. It is also revealed that the fill factor (FF) is also affected by the photon recycling effect, where incorporating SF results in the FF enhancement compared to the counterpart without the SF and the enhancement is higher for those with DBRs than without the DBRs.