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32 results on '"Shen, Tun-Li"'

12. Synthesis and Characterization of a Magnetically Active 19F Molecular Beacon

Author

Dempsey, Megan E., Marble, Hetal D., Shen, Tun-Li, Fawzi, Nicolas L., and Darling, Eric M.

Abstract

Gene expression is used extensively to describe cellular characteristics and behaviors; however, most methods of assessing gene expression are unsuitable for living samples, requiring destructive processes such as fixation or lysis. Recently, molecular beacons have become a viable tool for live-cell imaging of mRNA molecules in situ. Historically, beacon-mediated imaging has been limited to fluorescence-based approaches. We propose the design and synthesis of a novel molecular beacon for magnetic resonance detection of any desired target nucleotide sequence. The biologically compatible synthesis incorporates commonly used bioconjugation reactions in aqueous conditions and is accessible for laboratories without extensive synthesis capabilities. The resulting beacon uses fluorine (19F) as a reporter, which is broadened, or turned “off”, via paramagnetic relaxation enhancement from a stabilized nitroxide radical spin label when the beacon is not bound to its nucleic acid target. Therefore, the 19F NMR signal of the beacon is quenched in its hairpin conformation when the spin label and the 19F substituent are held in proximity, but the signal is recovered upon beacon hybridization to its specific complementary nucleotide sequence by physical separation of the radical from the 19F reporter. This study establishes a path for magnetic resonance-based assessment of specific mRNA expression, providing new possibilities for applying molecular beacon technology in living systems.

Published
2024
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16. Efficacy of a Non-Hypercalcemic Vitamin-D2 Derived Anti-Cancer Agent (MT19c) and Inhibition of Fatty Acid Synthesis in an Ovarian Cancer Xenograft Model

Author

Moore, Richard G., primary, Lange, Thilo S., additional, Robinson, Katina, additional, Kim, Kyu K., additional, Uzun, Alper, additional, Horan, Timothy C., additional, Kawar, Nada, additional, Yano, Naohiro, additional, Chu, Sharon R., additional, Mao, Quanfu, additional, Brard, Laurent, additional, DePaepe, Monique E., additional, Padbury, James F., additional, Arnold, Leggy A., additional, Brodsky, Alexander, additional, Shen, Tun-Li, additional, and Singh, Rakesh K., additional

Published
2012
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20. Liquid Chromatography-Mass Spectrometry and Tandem Mass Spectrometry of Peptides and Proteins.

Author

Walker, John M., Aguilar, Marie-Isabel, Shen, Tun-Li, and Noon, Kathleen R.

Abstract

Mass spectrometry has become one of the preferred methods of detection for high-performance liquid chromatography (HPLC) analyses of biopolymers for a broad range of applications. The primary reason for its widespread use is the value of the information obtained from these types of measurements. When liquid chromatography is interfaced directly to mass spectrometry (LC-MS), molecular weight information can be retrieved from the mass spectra acquired continuously as various components elute from the chromatographic column. In some cases, the identity of the protein or peptide can be assigned immediately if the mass measurements are determined with sufficient accuracy. However, it is more likely that additional information regarding molecular structure is required for identification. In tandem mass spectrometry experiments (LC-MS/MS), structural data are readily generated by fragmentation of peptides (or protein-derived peptides) in the mass spectrometer using the technique of collision-induced dissociation (CID). The fragments generated with CID all originate from the precursor; thus, supplementary information relating to the primary sequence and post-translational modifications of the protein or peptide is obtained. [ABSTRACT FROM AUTHOR]

Published
2004
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28. Fetal globin expression in New World monkeys.

Author

Johnson, Robert M., primary, Buck, Steven, additional, Chiu, Chi-hua, additional, Schneider, Horacio, additional, Sampaio, Iracilda, additional, Gage, Douglas A., additional, Shen, Tun-Li, additional, Schneider, Maria Paula C., additional, Muniz, José A., additional, Gumucio, Deborah L., additional, and Goodman, Morris, additional

Published
1996
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29. A Sweet H2S/H2O2Dual Release System and Specific Protein S-Persulfidation Mediated by Thioglucose/Glucose Oxidase

Author

Ni, Xiang, Li, Xiaolu, Shen, Tun-Li, Qian, Wei-Jun, and Xian, Ming

Abstract

H2S and H2O2are two redox regulating molecules that play important roles in many physiological and pathological processes. While each of them has distinct biosynthetic pathways and signaling mechanisms, the crosstalk between these two species is also known to cause critical biological responses such as protein S-persulfidation. So far, many chemical tools for the studies of H2S and H2O2have been developed, such as the donors and sensors for H2S and H2O2. However, these tools are normally targeting single species (e.g., only H2S or only H2O2). As such, the crosstalk and synergetic effects between H2S and H2O2have hardly been studied with those tools. In this work, we report a unique H2S/H2O2dual donor system by employing 1-thio-β-d-glucose and glucose oxidase (GOx) as the substrates. This enzymatic system can simultaneously produce H2S and H2O2in a slow and controllable fashion, without generating any bio-unfriendly byproducts. This system was demonstrated to cause efficient S-persulfidation on proteins. In addition, we expanded the system to thiolactose and thioglucose-disulfide; therefore, additional factors (β-galactosidase and cellular reductants) could be introduced to further control the release of H2S/H2O2. This dual release system should be useful for future research on H2S and H2O2.

Published
2021
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30. A Sweet H 2 S/H 2 O 2 Dual Release System and Specific Protein S-Persulfidation Mediated by Thioglucose/Glucose Oxidase.

Author

Ni X, Li X, Shen TL, Qian WJ, and Xian M

Subjects
Glucose chemistry, Glucose metabolism, Glucose Oxidase chemistry, Humans, Hydrogen Peroxide chemistry, Hydrogen Sulfide chemistry, Protein S chemistry, Glucose analogs & derivatives, Glucose Oxidase metabolism, Hydrogen Peroxide metabolism, Hydrogen Sulfide metabolism, Protein S metabolism
Abstract

H 2 S and H 2 O 2 are two redox regulating molecules that play important roles in many physiological and pathological processes. While each of them has distinct biosynthetic pathways and signaling mechanisms, the crosstalk between these two species is also known to cause critical biological responses such as protein S-persulfidation. So far, many chemical tools for the studies of H 2 S and H 2 O 2 have been developed, such as the donors and sensors for H 2 S and H 2 O 2 . However, these tools are normally targeting single species (e.g., only H 2 S or only H 2 O 2 ). As such, the crosstalk and synergetic effects between H 2 S and H 2 O 2 have hardly been studied with those tools. In this work, we report a unique H 2 S/H 2 O 2 dual donor system by employing 1-thio-β-d-glucose and glucose oxidase (GOx) as the substrates. This enzymatic system can simultaneously produce H 2 S and H 2 O 2 in a slow and controllable fashion, without generating any bio-unfriendly byproducts. This system was demonstrated to cause efficient S-persulfidation on proteins. In addition, we expanded the system to thiolactose and thioglucose-disulfide; therefore, additional factors (β-galactosidase and cellular reductants) could be introduced to further control the release of H 2 S/H 2 O 2 . This dual release system should be useful for future research on H 2 S and H 2 O 2 .

Published
2021
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31. Synthesis and Characterization of a Magnetically Active 19 F Molecular Beacon.

Author

Dempsey ME, Marble HD, Shen TL, Fawzi NL, and Darling EM

Subjects
Gene Expression, Nucleic Acid Hybridization methods, Oligonucleotide Probes genetics, RNA, Messenger genetics, Fluorescent Dyes chemistry, Fluorine chemistry, Magnetic Resonance Spectroscopy methods, Oligonucleotide Probes chemistry, RNA, Messenger analysis
Abstract

Gene expression is used extensively to describe cellular characteristics and behaviors; however, most methods of assessing gene expression are unsuitable for living samples, requiring destructive processes such as fixation or lysis. Recently, molecular beacons have become a viable tool for live-cell imaging of mRNA molecules in situ. Historically, beacon-mediated imaging has been limited to fluorescence-based approaches. We propose the design and synthesis of a novel molecular beacon for magnetic resonance detection of any desired target nucleotide sequence. The biologically compatible synthesis incorporates commonly used bioconjugation reactions in aqueous conditions and is accessible for laboratories without extensive synthesis capabilities. The resulting beacon uses fluorine ( 19 F) as a reporter, which is broadened, or turned "off", via paramagnetic relaxation enhancement from a stabilized nitroxide radical spin label when the beacon is not bound to its nucleic acid target. Therefore, the 19 F NMR signal of the beacon is quenched in its hairpin conformation when the spin label and the 19 F substituent are held in proximity, but the signal is recovered upon beacon hybridization to its specific complementary nucleotide sequence by physical separation of the radical from the 19 F reporter. This study establishes a path for magnetic resonance-based assessment of specific mRNA expression, providing new possibilities for applying molecular beacon technology in living systems.

Published
2018
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32. Liquid chromatography-mass spectrometry and tandem mass spectrometry of peptides and proteins.

Author

Shen TL and Noon KR

Subjects
Chromatography, Liquid instrumentation, Chromatography, Liquid methods, Computational Biology methods, Databases, Protein, Mass Spectrometry instrumentation, Mass Spectrometry methods, Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization methods, Peptides analysis, Peptides isolation & purification, Proteins analysis, Proteins isolation & purification
Published
2004
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