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191 results on '"Lippert, Alexander R."'

19. Azide-based fluorescent probes: imaging hydrogen sulfide in living systems.

Author

Lin, Vivian S, Lippert, Alexander R, and Chang, Christopher J

Subjects
Cells, Cultured, Humans, Hydrogen Sulfide, Azides, Vascular Endothelial Growth Factor A, Fluorescent Dyes, Microscopy, Fluorescence, Cell Culture Techniques, Staining and Labeling, Human Umbilical Vein Endothelial Cells, Azide reduction, Fluorescence, Hydrogen sulfide, Microscopy, Reaction-based sensing, Redox biology, Biochemistry & Molecular Biology, Biochemistry and Cell Biology
Abstract

Hydrogen sulfide is a redox active sulfur species that is endogenously generated in mammalian systems as an antioxidant and signaling molecule to support cellular function. The fundamental and ubiquitous actions of hydrogen sulfide demand sensitive and specific methods to track this biomolecule as it is produced within living organisms with temporal and spatial regulation. In this context, the hydrogen sulfide-mediated reduction of an azide to an amine is a useful method for organic synthesis, and this reaction has successfully been exploited to yield biocompatible fluorescent probes for hydrogen sulfide detection in vitro and in cells. This chapter provides protocols and guidelines for applying azide-based fluorescence probes to detecting hydrogen sulfide in living systems, including a protocol that was used to detect endogenous hydrogen sulfide in living single cells using a confocal microscope.

Published
2015

20. Chapter Four Azide-Based Fluorescent Probes Imaging Hydrogen Sulfide in Living Systems

Author

Lin, Vivian S, Lippert, Alexander R, and Chang, Christopher J

Subjects
Biochemistry and Cell Biology, Biological Sciences, Generic health relevance, Azides, Cell Culture Techniques, Cells, Cultured, Fluorescent Dyes, Human Umbilical Vein Endothelial Cells, Humans, Hydrogen Sulfide, Microscopy, Fluorescence, Staining and Labeling, Vascular Endothelial Growth Factor A, Azide reduction, Fluorescence, Hydrogen sulfide, Microscopy, Reaction-based sensing, Redox biology, Biochemistry & Molecular Biology, Biochemistry and cell biology
Abstract

Hydrogen sulfide is a redox active sulfur species that is endogenously generated in mammalian systems as an antioxidant and signaling molecule to support cellular function. The fundamental and ubiquitous actions of hydrogen sulfide demand sensitive and specific methods to track this biomolecule as it is produced within living organisms with temporal and spatial regulation. In this context, the hydrogen sulfide-mediated reduction of an azide to an amine is a useful method for organic synthesis, and this reaction has successfully been exploited to yield biocompatible fluorescent probes for hydrogen sulfide detection in vitro and in cells. This chapter provides protocols and guidelines for applying azide-based fluorescence probes to detecting hydrogen sulfide in living systems, including a protocol that was used to detect endogenous hydrogen sulfide in living single cells using a confocal microscope.

Published
2015

24. A chemiluminescent probe for cellular peroxynitrite using a self-immolative oxidative decarbonylation reaction† †Electronic supplementary information (ESI) available: Additional experimental details, supplementary figures, and scanned spectra. See DOI: 10.1039/c7sc05087a

Author

Cao, Jian, An, Weiwei, Reeves, Audrey G., and Lippert, Alexander R.

Subjects
Chemistry
Abstract

Peroxynitrite is a damaging agent of oxidative stress that has been difficult to monitor in living cells. Here, an isatin-based chemiluminescent probe for peroxynitrite is reported., Peroxynitrite (ONOO–) is a highly reactive oxygen species which has been recognized as an endogenous mediator of physiological activities like the immune response as well as a damaging agent of oxidative stress under pathological conditions. While its biological importance is becoming clearer, many of the details of its production and mechanism of action remain elusive due to the lack of available selective and sensitive detection methods. Herein, we report the development, characterization, and biological applications of a reaction-based chemiluminescent probe for ONOO– detection, termed as PNCL. PNCL reacts with ONOO–via an isatin moiety through an oxidative decarbonylation reaction to initiate light emission that can be observed instantly with high selectivity against other reactive sulphur, oxygen, and nitrogen species. Detailed studies were performed to study the reaction between isatin and ONOO–, which confirm selectivity for ONOO– over NO2˙. PNCL has been applied for ONOO– detection in aqueous solution and live cells. Moreover, PNCL can be employed to detect cellular ONOO– generated in macrophages stimulated to mount an immune response with lipopolysaccharide (LPS). The sensitivity granted by chemiluminescent detection together with the specificity of the oxidative decarbonylation reaction provides a useful tool to explore ONOO– chemistry and biology.

Published
2018

36. Visible Light Chemical Micropatterning Using a Digital Light Processing Fluorescence Microscope

Author

Haris, Uroob, Plank, Joshua T., Li, Bo, Page, Zachariah A., and Lippert, Alexander R.

Abstract

Patterning chemical reactivity with a high spatiotemporal resolution and chemical versatility is critically important for advancing revolutionary emergent technologies, including nanorobotics, bioprinting, and photopharmacology. Current methods are complex and costly, necessitating novel techniques that are easy to use and compatible with a wide range of chemical functionalities. This study reports the development of a digital light processing (DLP) fluorescence microscope that enables the structuring of visible light (465–625 nm) for high-resolution photochemical patterning and simultaneous fluorescence imaging of patterned samples. A range of visible-light-driven photochemical systems, including thiol–ene photoclick reactions, Wolff rearrangements of diazoketones, and photopolymerizations, are shown to be compatible with this system. Patterning the chemical functionality onto microscopic polymer beads and films is accomplished with photographic quality and resolutions as high as 2.1 μm for Wolff rearrangement chemistry and 5 μm for thiol–ene chemistry. Photoactivation of molecules in living cells is demonstrated with single-cell resolution, and microscale 3D printing is achieved using a polymer resin with a 20 μm xy-resolution and a 100 μm z-resolution. Altogether, this work debuts a powerful and easy-to-use platform that will facilitate next-generation nanorobotic, 3D printing, and metamaterial technologies.

Published
2022
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38. Tuning the Photophysical Properties of Spirolactam Rhodamine Photoswitches.

Author

Li, Bo, Haris, Uroob, Aljowni, Maha, Nakatsuka, Andrew, Patel, Shreya K., and Lippert, Alexander R.

Subjects
FLUORESCENCE yield, RHODAMINES, MOLECULAR structure, SINGLE molecules, TRIFLUOROACETIC acid, EQUILIBRIUM reactions
Abstract

Spirolactam rhodamines are fluorescent photoswitches that are useful for single molecule localization microscopy, volumetric 3D digital light photoactivatable dye displays, and other applications. Measurement of the photophysical properties, particularly photoswitching kinetics and quantum yields, is challenging and a comprehensive understanding of how molecular structure affects these parameters remains incomplete. In this study, we have synthesized a series of N‐aryl spirolactam rhodamine photoswitches with fluorescent emissions at 585 nm and 518 nm. Extinction coefficients and fluorescence quantum yields of the fluorescent form of the photoswitch have been measured using excess trifluoroacetic acid to drive the equilibrium to the open form. A method to determine photoswitching kinetics and quantum yields was developed by monitoring the kinetics to reach equilibrium between the on‐state and off‐state and fitting this data to a rate equation for a reaction in equilibrium. Trends based on the electronic and steric properties of the aryl substituents were evaluated. Using this information, a proof‐of‐principle demonstration of 3D voxel formation was accomplished using a green (518 nm) emitting photoswitch, setting the foundation for a multi‐colour volumetric 3D display. [ABSTRACT FROM AUTHOR]

Published
2021
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45. Synthesis of phototrappable shape-shifting molecules for adaptive guest binding

Author

Lippert, Alexander R., Naganawa, Atsushi, Keleshian, Vasken L., and Bode, Jeffrey W.

Subjects
Olefins -- Chemical properties, Carbonates -- Structure, Carbonates -- Chemical properties, Porphyrins -- Structure, Porphyrins -- Chemical properties, Substitution reactions -- Analysis, Chemistry
Abstract

A study was conducted to design and synthesize oligosubstituted bullvalenes as adaptive molecules that could change their shapes in order to bind tightly to a suitable guest. Tightly binding species could be selectively isolated from a population of hundreds of interconverting structural isomers by incorporating a photolabile o-nitroveratryloxycarbonate (NVOC) group into bullvalenes.

Published
2010

46. Stereoretentive synthesis and chemoselective amide-forming ligations of C-terminal peptide [alpha]-ketoacids

Author

Lei Ju, Lippert, Alexander R., and Bode, Jeffrey W.

Subjects
Amides -- Structure, Amides -- Chemical properties, Oxidation-reduction reaction -- Analysis, Ylides -- Structure, Ylides -- Chemical properties, Phosphorus compounds -- Structure, Phosphorus compounds -- Chemical properties, Chemistry
Abstract

A chemoselective synthetic method to obtain C-terminal peptide [alpha]-ketoacids with minimal epimerization is described. The approach with solid-phase modifications can also be used to prepare longer [alpha]-peptide derived [alpha]-ketoacids suitable for use in decarboxylative peptide ligation reactions.

Published
2008

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