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Feng RR, Wang M, Zhang W, Gai F. Unnatural Amino Acids for Biological Spectroscopy and Microscopy. Chem Rev 2024; 124:6501-6542. [PMID: 38722769 DOI: 10.1021/acs.chemrev.3c00944] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/23/2024]
Abstract
Due to advances in methods for site-specific incorporation of unnatural amino acids (UAAs) into proteins, a large number of UAAs with tailored chemical and/or physical properties have been developed and used in a wide array of biological applications. In particular, UAAs with specific spectroscopic characteristics can be used as external reporters to produce additional signals, hence increasing the information content obtainable in protein spectroscopic and/or imaging measurements. In this Review, we summarize the progress in the past two decades in the development of such UAAs and their applications in biological spectroscopy and microscopy, with a focus on UAAs that can be used as site-specific vibrational, fluorescence, electron paramagnetic resonance (EPR), or nuclear magnetic resonance (NMR) probes. Wherever applicable, we also discuss future directions.
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Affiliation(s)
- Ran-Ran Feng
- Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Manxi Wang
- Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Wenkai Zhang
- Department of Physics and Applied Optics Beijing Area Major Laboratory, Beijing Normal University, Beijing 100875, China
| | - Feng Gai
- Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
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Allert MJ, Kumar S, Wang Y, Beese LS, Hellinga HW. Chromophore carbonyl twisting in fluorescent biosensors encodes direct readout of protein conformations with multicolor switching. Commun Chem 2023; 6:168. [PMID: 37598249 PMCID: PMC10439942 DOI: 10.1038/s42004-023-00982-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2023] [Accepted: 08/11/2023] [Indexed: 08/21/2023] Open
Abstract
Fluorescent labeling of proteins is a powerful tool for probing structure-function relationships with many biosensing applications. Structure-based rules for systematically designing fluorescent biosensors require understanding ligand-mediated fluorescent response mechanisms which can be challenging to establish. We installed thiol-reactive derivatives of the naphthalene-based fluorophore Prodan into bacterial periplasmic glucose-binding proteins. Glucose binding elicited paired color exchanges in the excited and ground states of these conjugates. X-ray structures and mutagenesis studies established that glucose-mediated color switching arises from steric interactions that couple protein conformational changes to twisting of the Prodan carbonyl relative to its naphthalene plane. Mutations of residues contacting the carbonyl can optimize color switching by altering fluorophore conformational equilibria in the apo and glucose-bound proteins. A commonly accepted view is that Prodan derivatives report on protein conformations via solvatochromic effects due to changes in the dielectric of their local environment. Here we show that instead Prodan carbonyl twisting controls color switching. These insights enable structure-based biosensor design by coupling ligand-mediated protein conformational changes to internal chromophore twists through specific steric interactions between fluorophore and protein.
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Affiliation(s)
- Malin J Allert
- Department of Biochemistry, Duke University Medical Center, Durham, NC, 27710, USA
| | - Shivesh Kumar
- Department of Biochemistry, Duke University Medical Center, Durham, NC, 27710, USA
- Department of Biochemistry and Molecular Biophysics, Washington University in St. Louis, St. Louis, MO, 63110, USA
| | - You Wang
- Department of Biochemistry, Duke University Medical Center, Durham, NC, 27710, USA
| | - Lorena S Beese
- Department of Biochemistry, Duke University Medical Center, Durham, NC, 27710, USA
| | - Homme W Hellinga
- Department of Biochemistry, Duke University Medical Center, Durham, NC, 27710, USA.
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3
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Islam J, Conroy P, Fercher C, Kim M, Yaari Z, Jones M, Bell TDM, Caradoc-Davies T, Law R, Whisstock J, Heller D, Mahler S, Corrie S. Design of Polarity-Dependent Immunosensors Based on the Structural Analysis of Engineered Antibodies. ACS Chem Biol 2023; 18:1863-1871. [PMID: 37440171 DOI: 10.1021/acschembio.3c00303] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/14/2023]
Abstract
"Reagentless" immunosensors are emerging to address the challenge of practical and sensitive detection of important biomarkers in real biological samples without the need for multistep assays and user intervention, with applications ranging from research tools to point-of-care diagnostics. Selective target binding to an affinity reagent is detected and reported in one step without the need for washing or additional reporters. In this study, we used a structure-guided approach to identify a mutation site in an antibody fragment for the polarity-dependent fluorophore, Anap, such that upon binding of the protein target cardiac troponin I, the Anap-labeled antibody would produce a detectable and dose-dependent shift in emission wavelength. We observed a significant emission wavelength shift of the Anap-labeled anti-cTnI mutant, with a blue shift of up to 37 nm, upon binding to the cTnI protein. Key differences in the resulting emission spectra between target peptides in comparison to whole proteins were also found; however, the affinity and binding characteristics remained unaffected when compared to the wild-type antibody. We also highlighted the potential flexibility of the approach by incorporating a near-infrared dye, IRDye800CW, into the same mutation site, which also resulted in a dose-dependent wavelength shift upon target incubation. These reagents can be used in experiments and devices to create simpler and more efficient biosensors across a range of research, medical laboratory, and point-of-care platforms.
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Affiliation(s)
- Jiaul Islam
- Department of Chemical and Biological Engineering, Monash University, Melbourne 3800, Australia
| | - Paul Conroy
- Dept. of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Monash University, Melbourne 3800, Australia
| | - Christian Fercher
- Australian Institute for Bioengineering and Nanotechnology (AIBN), The University of Queensland, Brisbane 4072, Australia
- ARC Training Centre for Biopharmaceutical Innovation, Australian Institute for Bioengineering and Nanotechnology (AIBN), The University of Queensland, Brisbane 4072, Australia
| | - Mijin Kim
- Molecular Pharmacology Program, Memorial Sloan Kettering Cancer Centre, New York 10065, United States
| | - Zvi Yaari
- Molecular Pharmacology Program, Memorial Sloan Kettering Cancer Centre, New York 10065, United States
- School of Pharmacy, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem 91905, Israel
| | - Martina Jones
- Australian Institute for Bioengineering and Nanotechnology (AIBN), The University of Queensland, Brisbane 4072, Australia
- ARC Training Centre for Biopharmaceutical Innovation, Australian Institute for Bioengineering and Nanotechnology (AIBN), The University of Queensland, Brisbane 4072, Australia
| | - Toby D M Bell
- School of Chemistry, Monash University, Melbourne 3800, Australia
| | - Tom Caradoc-Davies
- Dept. of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Monash University, Melbourne 3800, Australia
- Australian Synchrotron - ANSTO, Melbourne 3168, Australia
| | - Ruby Law
- Dept. of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Monash University, Melbourne 3800, Australia
| | - James Whisstock
- Dept. of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Monash University, Melbourne 3800, Australia
| | - Daniel Heller
- Molecular Pharmacology Program, Memorial Sloan Kettering Cancer Centre, New York 10065, United States
| | - Stephen Mahler
- Dept. of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Monash University, Melbourne 3800, Australia
- Australian Institute for Bioengineering and Nanotechnology (AIBN), The University of Queensland, Brisbane 4072, Australia
| | - Simon Corrie
- Department of Chemical and Biological Engineering, Monash University, Melbourne 3800, Australia
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Huynh GT, Kesarwani V, Walker JA, Frith JE, Meagher L, Corrie SR. Review: Nanomaterials for Reactive Oxygen Species Detection and Monitoring in Biological Environments. Front Chem 2021; 9:728717. [PMID: 34568279 PMCID: PMC8461210 DOI: 10.3389/fchem.2021.728717] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2021] [Accepted: 08/25/2021] [Indexed: 12/19/2022] Open
Abstract
Reactive oxygen species (ROS) and dissolved oxygen play key roles across many biological processes, and fluorescent stains and dyes are the primary tools used to quantify these species in vitro. However, spatio-temporal monitoring of ROS and dissolved oxygen in biological systems are challenging due to issues including poor photostability, lack of reversibility, and rapid off-site diffusion. In particular, ROS monitoring is hindered by the short lifetime of ROS molecules and their low abundance. The combination of nanomaterials and fluorescent detection has led to new opportunities for development of imaging probes, sensors, and theranostic products, because the scaffolds lead to improved optical properties, tuneable interactions with cells and media, and ratiometric sensing robust to environmental drift. In this review, we aim to critically assess and highlight recent development in nanosensors and nanomaterials used for the detection of oxygen and ROS in biological systems, and their future potential use as diagnosis tools.
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Affiliation(s)
- Gabriel T. Huynh
- Department of Chemical Engineering, Monash University, Clayton, VIC, Australia
- ARC Centre of Excellence in Convergent Bio-Nano Science and Technology, Monash Node, Clayton, VIC, Australia
| | - Vidhishri Kesarwani
- Department of Chemical Engineering, Monash University, Clayton, VIC, Australia
- ARC Centre of Excellence in Convergent Bio-Nano Science and Technology, Monash Node, Clayton, VIC, Australia
| | - Julia A. Walker
- Department of Chemical Engineering, Monash University, Clayton, VIC, Australia
- ARC Centre of Excellence in Convergent Bio-Nano Science and Technology, Monash Node, Clayton, VIC, Australia
| | - Jessica E. Frith
- Monash Institute of Medical Engineering, Monash University, Clayton, VIC, Australia
- Department of Material Science and Engineering, Monash University, Clayton, VIC, Australia
- ARC Training Centre for Cell and Tissue Engineering Technologies, Monash University, Clayton, VIC, Australia
| | - Laurence Meagher
- Department of Material Science and Engineering, Monash University, Clayton, VIC, Australia
- ARC Training Centre for Cell and Tissue Engineering Technologies, Monash University, Clayton, VIC, Australia
| | - Simon R. Corrie
- Department of Chemical Engineering, Monash University, Clayton, VIC, Australia
- ARC Centre of Excellence in Convergent Bio-Nano Science and Technology, Monash Node, Clayton, VIC, Australia
- ARC Training Centre for Cell and Tissue Engineering Technologies, Monash University, Clayton, VIC, Australia
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Fercher C, Jones ML, Mahler SM, Corrie SR. Recombinant Antibody Engineering Enables Reversible Binding for Continuous Protein Biosensing. ACS Sens 2021; 6:764-776. [PMID: 33481587 DOI: 10.1021/acssensors.0c01510] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Engineering antibodies to improve target specificity, reduce detection limits, or introduce novel functionality is an important research area for biosensor development. While various affinity biosensors have been developed to generate an output signal upon varying analyte concentrations, reversible and continuous protein monitoring in complex biological samples remains challenging. Herein, we explore the concept of directed evolution to modulate dissociation kinetics of a high affinity anti-epidermal growth factor receptor (EGFR) single-chain variable antibody fragment (scFv) to enable continuous protein sensing in a label-free binding assay. A mutant scFv library was generated from the wild type (WT) fragment via targeted permutation of four residues in the antibody-antigen-binding interface. A single round of phage display biopanning complemented with high-throughput screening methods then permitted isolation of a specific binder with fast reaction kinetics. We were able to obtain ∼30 times faster dissociation rates when compared to the WT without appreciably affecting overall affinity and specificity by targeting a single paratope that is known to contribute to the binding interaction. Suitability of a resulting mutant fragment to sense varying antigen concentrations in continuous mode was demonstrated in a modified label-free binding assay, achieving low nanomolar detection limits (KD = 8.39 nM). We also confirmed these results using an independent detection mechanism developed previously by our group, incorporating a polarity-dependent fluorescent dye into the scFv and reading out EGFR binding based on fluorescence wavelength shifts. In future, this generic approach could be employed to generate improved or novel binders for proteins of interest, ready for deployment in a broad range of assay platforms.
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Affiliation(s)
- Christian Fercher
- Australian Institute for Bioengineering and Nanotechnology, ARC Training Centre for Biopharmaceutical Innovation, The University of Queensland, St. Lucia, Queensland, 4072 Australia
- Australian Institute for Bioengineering and Nanotechnology, ARC Centre of Excellence in Convergent Bio-Nano Science and Technology, The University of Queensland, St. Lucia, Queensland, 4072 Australia
| | - Martina L. Jones
- Australian Institute for Bioengineering and Nanotechnology, ARC Training Centre for Biopharmaceutical Innovation, The University of Queensland, St. Lucia, Queensland, 4072 Australia
| | - Stephen M. Mahler
- Australian Institute for Bioengineering and Nanotechnology, ARC Training Centre for Biopharmaceutical Innovation, The University of Queensland, St. Lucia, Queensland, 4072 Australia
| | - Simon R. Corrie
- Department of Chemical Engineering, ARC Centre of Excellence in Convergent Bio-Nano Science and Technology, Monash University, Clayton, Victoria 3800 Australia
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Abstract
Fluorescence spectroscopy and microscopy are non-destructive methods that provide real-time measurements of ion channel structural dynamics. As such, they constitute a direct path linking the high-resolution structural models from X-ray crystallography and cryo-electron microscopy with the high-resolution functional data from ionic current measurements. The utility of fluorescence as a reporter of channel structure is limited by the palette of available fluorophores. Thiol-reactive fluorophores are small and bright, but are restricted in terms of the positions on a protein that can be labeled and present significant issues with background incorporation. Genetically encoded fluorescent protein tags are specific to a protein of interest, but are very large and usually only used to label the free N- and C-termini of proteins. L-3-(6-acetylnaphthalen-2-ylamino)-2-aminopropionic acid (ANAP) is a fluorescent amino acid that can be specifically incorporated into virtually any site on a protein of interest using amber stop-codon suppression. Due to its environmental sensitivity and potential as a donor in fluorescence resonance energy transfer experiments, it has been adopted by numerous investigators to study voltage, ligand, and temperature-dependent activation of a host of ion channels. Simultaneous measurements of ionic currents and ANAP fluorescence yield exceptional mechanistic insights into channel function. In this chapter, I will summarize the current literature regarding ANAP and ion channels and discuss the practical aspects of using ANAP, including potential pitfalls and confounds.
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Dong J, Ueda H. Recent Advances in Quenchbody, a Fluorescent Immunosensor. SENSORS 2021; 21:s21041223. [PMID: 33572319 PMCID: PMC7916128 DOI: 10.3390/s21041223] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/26/2020] [Revised: 01/27/2021] [Accepted: 02/06/2021] [Indexed: 12/29/2022]
Abstract
The detection of viruses, disease biomarkers, physiologically active substances, drugs, and chemicals is of great significance in many areas of our lives. Immunodetection technology is based on the specificity and affinity of antigen–antibody reactions. Compared with other analytical methods such as liquid chromatography coupled with mass spectrometry, which requires a large and expensive instrument, immunodetection has the advantages of simplicity and good selectivity and is thus widely used in disease diagnosis and food/environmental monitoring. Quenchbody (Q-body), a new type of fluorescent immunosensor, is an antibody fragment labeled with fluorescent dyes. When the Q-body binds to its antigen, the fluorescence intensity increases. The detection of antigens by changes in fluorescence intensity is simple, easy to operate, and highly sensitive. This review comprehensively discusses the principle, construction, application, and current progress related to Q-bodies.
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Affiliation(s)
- Jinhua Dong
- Tokyo Tech World Research Hub Initiative (WRHI), Institute of Innovative Research, Tokyo Institute of Technology, Yokohama 226-8503, Japan;
- Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, Yokohama 226-8503, Japan
- School of Life Science and Technology, Weifang Medical University, Weifang 261053, China
| | - Hiroshi Ueda
- Tokyo Tech World Research Hub Initiative (WRHI), Institute of Innovative Research, Tokyo Institute of Technology, Yokohama 226-8503, Japan;
- Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, Yokohama 226-8503, Japan
- Correspondence: ; Tel.: +81-45-924-5256
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Chandler PG, Buckle AM. Development and Differentiation in Monobodies Based on the Fibronectin Type 3 Domain. Cells 2020; 9:E610. [PMID: 32143310 PMCID: PMC7140400 DOI: 10.3390/cells9030610] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Revised: 02/24/2020] [Accepted: 03/01/2020] [Indexed: 12/13/2022] Open
Abstract
As a non-antibody scaffold, monobodies based on the fibronectin type III (FN3) domain overcome antibody size and complexity while maintaining analogous binding loops. However, antibodies and their derivatives remain the gold standard for the design of new therapeutics. In response, clinical-stage therapeutic proteins based on the FN3 domain are beginning to use native fibronectin function as a point of differentiation. The small and simple structure of monomeric monobodies confers increased tissue distribution and reduced half-life, whilst the absence of disulphide bonds improves stability in cytosolic environments. Where multi-specificity is challenging with an antibody format that is prone to mis-pairing between chains, multiple FN3 domains in the fibronectin assembly already interact with a large number of molecules. As such, multiple monobodies engineered for interaction with therapeutic targets are being combined in a similar beads-on-a-string assembly which improves both efficacy and pharmacokinetics. Furthermore, full length fibronectin is able to fold into multiple conformations as part of its natural function and a greater understanding of how mechanical forces allow for the transition between states will lead to advanced applications that truly differentiate the FN3 domain as a therapeutic scaffold.
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Affiliation(s)
- Peter G. Chandler
- Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Monash University, Clayton 3800, Australia;
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