1
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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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2
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Meng W, Peng HC, Liu Y, Stelling A, Wang L. Modeling the Infrared Spectroscopy of Oligonucleotides with 13C Isotope Labels. J Phys Chem B 2023; 127:2351-2361. [PMID: 36898003 DOI: 10.1021/acs.jpcb.2c08915] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/12/2023]
Abstract
The carbonyl stretching modes have been widely used in linear and two-dimensional infrared (IR) spectroscopy to probe the conformation, interaction, and biological functions of nucleic acids. However, due to their universal appearance in nucleobases, the IR absorption bands of nucleic acids are often highly congested in the 1600-1800 cm-1 region. Following the fruitful applications in proteins, 13C isotope labels have been introduced to the IR measurements of oligonucleotides to reveal their site-specific structural fluctuations and hydrogen bonding conditions. In this work, we combine recently developed frequency and coupling maps to develop a theoretical strategy that models the IR spectra of oligonucleotides with 13C labels directly from molecular dynamics simulations. We apply the theoretical method to nucleoside 5'-monophosphates and DNA double helices and demonstrate how elements of the vibrational Hamiltonian determine the spectral features and their changes upon isotope labeling. Using the double helices as examples, we show that the calculated IR spectra are in good agreement with experiments and the 13C isotope labeling technique can potentially be applied to characterize the stacking configurations and secondary structures of nucleic acids.
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Affiliation(s)
- Wenting Meng
- Department of Chemistry and Chemical Biology, Institute for Quantitative Biomedicine, Rutgers University, Piscataway, New Jersey 08854, United States
| | - Hao-Che Peng
- Department of Chemistry and Biochemistry, The University of Texas at Dallas, Richardson, Texas 75080, United States
| | - Yuanhao Liu
- Department of Statistics, Institute for Quantitative Biomedicine, Rutgers University, Piscataway, New Jersey 08854, United States
| | - Allison Stelling
- Department of Chemistry and Biochemistry, The University of Texas at Dallas, Richardson, Texas 75080, United States
| | - Lu Wang
- Department of Chemistry and Chemical Biology, Institute for Quantitative Biomedicine, Rutgers University, Piscataway, New Jersey 08854, United States
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3
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Caporaletti F, Bittermann MR, Bonn D, Woutersen S. Fluorescent molecular rotor probes nanosecond viscosity changes. J Chem Phys 2022; 156:201101. [DOI: 10.1063/5.0092248] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Viscosity is a key property of liquids, but it is difficult to measure in short-lived, metastable samples due to the long measuring times required by conventional rheology. Here, we show how this problem can be solved by using fluorescent molecular rotors. The excited-state fluorescence decay rate of these molecules is sensitive to the viscosity of their local environment, and by combining pulsed laser excitation with time-resolved fluorescence detection, we can measure viscosities with a time resolution of a few ns. We demonstrate this by measuring in real time the viscosity change in glycerol induced by a nanosecond temperature jump. This new approach makes it possible to measure the viscosity of extremely short-lived states of matter.
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Affiliation(s)
- Federico Caporaletti
- Van der Waals-Zeeman Institute, Institute of Physics, University of Amsterdam, 1098XH Amsterdam, The Netherlands
- Van ’t Hoff Institute for Molecular Sciences, University of Amsterdam, 1098XH Amsterdam, The Netherlands
| | - Marius R. Bittermann
- Van der Waals-Zeeman Institute, Institute of Physics, University of Amsterdam, 1098XH Amsterdam, The Netherlands
| | - Daniel Bonn
- Van der Waals-Zeeman Institute, Institute of Physics, University of Amsterdam, 1098XH Amsterdam, The Netherlands
| | - Sander Woutersen
- Van ’t Hoff Institute for Molecular Sciences, University of Amsterdam, 1098XH Amsterdam, The Netherlands
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4
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Siu HW, Hauser K. Observation of Oligomeric States Indicates a High Structural Flexibility Required for the Onset of Polyglutamine Fibrillization. J Phys Chem Lett 2022; 13:4543-4548. [PMID: 35580015 DOI: 10.1021/acs.jpclett.2c00203] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Polyglutamine (polyQ) diseases are caused by misfolding and aggregation of expanded polyQ tracts in the affected protein. PolyQ fibrils have been studied in detail; however, less is known about oligomeric precursor states. By a combination of time-resolved temperature-jump (T-jump) infrared (IR) spectroscopy and an appropriately tailored polyQ model peptide, we succeeded in disentangling conformational dynamics in the heterogeneous ensemble of states evolving during aggregation. Individual structural elements could be differentiated by IR-specific signatures, i.e., hairpin monomers, β-structured oligomers, and disordered structure. Submillisecond dynamics were observed for early oligomeric states in contrast to the slow dynamics of fibril growth. We propose that a high structural flexibility of oligomers is required to initiate fibril formation, but not after a fibrillar structure has consolidated and the fibril just grows. Our study reveals that structural flexibility changes at different stages in the aggregation process, from fibril initiation to fibril growth.
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Affiliation(s)
- Ho-Wah Siu
- Department of Chemistry, University of Konstanz, 78457 Konstanz, Germany
| | - Karin Hauser
- Department of Chemistry, University of Konstanz, 78457 Konstanz, Germany
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5
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PolyQ aggregation studied by model peptides with intrinsic tryptophan fluorophores. Biophys Chem 2022; 284:106782. [DOI: 10.1016/j.bpc.2022.106782] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Revised: 02/15/2022] [Accepted: 02/15/2022] [Indexed: 11/02/2022]
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6
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Fick RJ, Liu AY, Nussbaumer F, Kreutz C, Rangadurai A, Xu Y, Sommer RD, Shi H, Scheiner S, Stelling AL. Probing the Hydrogen-Bonding Environment of Individual Bases in DNA Duplexes with Isotope-Edited Infrared Spectroscopy. J Phys Chem B 2021; 125:7613-7627. [PMID: 34236202 PMCID: PMC8311644 DOI: 10.1021/acs.jpcb.1c01351] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
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Measuring the strength
of the hydrogen bonds between DNA base pairs
is of vital importance for understanding how our genetic code is physically
accessed and recognized in cells, particularly during replication
and transcription. Therefore, it is important to develop probes for
these key hydrogen bonds (H-bonds) that dictate events critical to
cellular function, such as the localized melting of DNA. The vibrations
of carbonyl bonds are well-known probes of their H-bonding environment,
and their signals can be observed with infrared (IR) spectroscopy.
Yet, pinpointing a single bond of interest in the complex IR spectrum
of DNA is challenging due to the large number of carbonyl signals
that overlap with each other. Here, we develop a method using isotope
editing and infrared (IR) spectroscopy to isolate IR signals from
the thymine (T) C2=O carbonyl. We use solvatochromatic studies
to show that the TC2=O signal’s position in the IR spectrum
is sensitive to the H-bonding capacity of the solvent. Our results
indicate that C2=O of a single T base within DNA duplexes experiences
weak H-bonding interactions. This finding is consistent with the existence
of a third, noncanonical CH···O H-bond between adenine
and thymine in both Watson–Crick and Hoogsteen base pairs in
DNA.
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Affiliation(s)
- Robert J Fick
- Department of Chemistry and Biochemistry, The University of Texas at Dallas, Richardson, Texas 75080, United States
| | - Amy Y Liu
- Department of Biochemistry, Duke University Medical Center, Durham, North Carolina 27710, United States
| | - Felix Nussbaumer
- Institute of Organic Chemistry and Center for Molecular Biosciences Innsbruck (CMBI), University of Innsbruck, Innsbruck 6020, Austria
| | - Christoph Kreutz
- Institute of Organic Chemistry and Center for Molecular Biosciences Innsbruck (CMBI), University of Innsbruck, Innsbruck 6020, Austria
| | - Atul Rangadurai
- Department of Biochemistry, Duke University Medical Center, Durham, North Carolina 27710, United States
| | - Yu Xu
- Department of Chemistry, Duke University, Durham, North Carolina 27710, United States
| | - Roger D Sommer
- Molecular Education, Technology, and Research Innovation Center, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Honglue Shi
- Department of Chemistry, Duke University, Durham, North Carolina 27710, United States
| | - Steve Scheiner
- Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322, United States
| | - Allison L Stelling
- Department of Chemistry and Biochemistry, The University of Texas at Dallas, Richardson, Texas 75080, United States.,Department of Biochemistry, Duke University Medical Center, Durham, North Carolina 27710, United States
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7
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Vosough F, Barth A. Characterization of Homogeneous and Heterogeneous Amyloid-β42 Oligomer Preparations with Biochemical Methods and Infrared Spectroscopy Reveals a Correlation between Infrared Spectrum and Oligomer Size. ACS Chem Neurosci 2021; 12:473-488. [PMID: 33455165 PMCID: PMC8023574 DOI: 10.1021/acschemneuro.0c00642] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
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Soluble oligomers of the amyloid-β(1-42)
(Aβ42) peptide,
widely considered to be among the relevant neurotoxic species involved
in Alzheimer’s disease, were characterized with a combination
of biochemical and biophysical methods. Homogeneous and stable Aβ42
oligomers were prepared by treating monomeric solutions of the peptide
with detergents. The prepared oligomeric solutions were analyzed with
blue native and sodium dodecyl sulfate polyacrylamide gel electrophoresis,
as well as with infrared (IR) spectroscopy. The IR spectra indicated
a well-defined β-sheet structure of the prepared oligomers.
We also found a relationship between the size/molecular weight of
the Aβ42 oligomers and their IR spectra: The position of the
main amide I′ band of the peptide backbone correlated with
oligomer size, with larger oligomers being associated with lower wavenumbers.
This relationship explained the time-dependent band shift observed
in time-resolved IR studies of Aβ42 aggregation in the absence
of detergents, during which the oligomer size increased. In addition,
the bandwidth of the main IR band in the amide I′ region was
found to become narrower with time in our time-resolved aggregation
experiments, indicating a more homogeneous absorption of the β-sheets
of the oligomers after several hours of aggregation. This is predominantly
due to the consumption of smaller oligomers in the aggregation process.
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Affiliation(s)
- Faraz Vosough
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm SE-106 91, Sweden
| | - Andreas Barth
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm SE-106 91, Sweden
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8
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Siu HW, Heck B, Kovermann M, Hauser K. Template-assisted design of monomeric polyQ models to unravel the unique role of glutamine side chains in disease-related aggregation. Chem Sci 2020; 12:412-426. [PMID: 33552461 PMCID: PMC7863018 DOI: 10.1039/d0sc05299j] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2020] [Accepted: 10/28/2020] [Indexed: 01/28/2023] Open
Abstract
PolyQ model peptides reveal the effect of individual glutamine side chains on fibril formation.
Expanded polyglutamine (polyQ) sequences cause numerous neurodegenerative diseases which are accompanied by the formation of polyQ fibrils. The unique role of glutamines in the aggregation onset is undoubtedly accepted and a lot structural data of the fibrils have been acquired, however side-chain specific structural dynamics inducing oligomerization are not well understood yet. To analyze spectroscopically the nucleation process, we designed various template-assisted glutamine-rich β-hairpin monomers mimicking the structural motif of a polyQ fibril. In a top-down strategy, we use a template which forms a well-defined stable hairpin in solution, insert polyQ-rich sequences into each strand and monitor the effects of individual glutamines by NMR, CD and IR spectroscopic approaches. The design was further advanced by alternating glutamines with other amino acids (T, W, E, K), thereby enhancing the solubility and increasing the number of cross-strand interacting glutamine side chains. Our spectroscopic studies reveal a decreasing hairpin stability with increased glutamine content and demonstrate the enormous impact of only a few glutamines – far below the disease threshold – to destabilize structure. Furthermore, we could access sub-ms conformational dynamics of monomeric polyQ-rich peptides by laser-excited temperature-jump IR spectroscopy. Both, the increased number of interacting glutamines and higher concentrations are key parameters to induce oligomerization. Concentration-dependent time-resolved IR measurements indicate an additional slower kinetic phase upon oligomer formation. The here presented peptide models enable spectroscopic molecular analyses to distinguish between monomer and oligomer dynamics in the early steps of polyQ fibril formation and in a side-chain specific manner.
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Affiliation(s)
- Ho-Wah Siu
- Department of Chemistry , University of Konstanz , 78457 Konstanz , Germany . ;
| | - Benjamin Heck
- Department of Chemistry , University of Konstanz , 78457 Konstanz , Germany . ;
| | - Michael Kovermann
- Department of Chemistry , University of Konstanz , 78457 Konstanz , Germany . ;
| | - Karin Hauser
- Department of Chemistry , University of Konstanz , 78457 Konstanz , Germany . ;
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9
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Keiderling TA. Structure of Condensed Phase Peptides: Insights from Vibrational Circular Dichroism and Raman Optical Activity Techniques. Chem Rev 2020; 120:3381-3419. [DOI: 10.1021/acs.chemrev.9b00636] [Citation(s) in RCA: 50] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Timothy A. Keiderling
- Department of Chemistry, University of Illinois at Chicago 845 West Taylor Street m/c 111, Chicago, Illinois 60607-7061, United States
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10
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Scheerer D, Chi H, McElheny D, Keiderling TA, Hauser K. Enhanced Sensitivity to Local Dynamics in Peptides by Use of Temperature-Jump IR Spectroscopy and Isotope Labeling. Chemistry 2020; 26:3524-3534. [PMID: 31782580 PMCID: PMC7155074 DOI: 10.1002/chem.201904497] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Indexed: 11/12/2022]
Abstract
Site-specific isotopic labeling of molecules is a widely used approach in IR spectroscopy to resolve local contributions to vibrational modes. The induced frequency shift of the corresponding IR band depends on the substituted masses, as well as on hydrogen bonding and vibrational coupling. The impact of these different factors was analyzed with a designed three-stranded β-sheet peptide and by use of selected 13 C isotope substitutions at multiple positions in the peptide backbone. Single-strand labels give rise to isotopically shifted bands at different frequencies, depending on the specific sites; this demonstrates sensitivity to the local environment. Cross-strand double- and triple-labeled peptides exhibited two resolved bands that could be uniquely assigned to specific residues, the equilibrium IR spectra of which indicated only weak local-mode coupling. Temperature-jump IR laser spectroscopy was applied to monitor structural dynamics and revealed an impressive enhancement of the isotope sensitivity to both local positions and coupling between them, relative to that of equilibrium FTIR spectroscopy. Site-specific relaxation rates were altered upon the introduction of additional cross-strand isotopes. Likewise, the rates for the global β-sheet dynamics were affected in a manner dependent on the distinct relaxation behavior of the labeled oscillator. This study reveals that isotope labels provide not only local structural probes, but rather sense the dynamic complexity of the molecular environment.
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Affiliation(s)
- David Scheerer
- Department of Chemistry, University of Konstanz, 78457, Konstanz, Germany
| | - Heng Chi
- Department of Chemistry, University of Illinois at Chicago, Chicago, IL, USA.,Jiangsu Food and Pharmaceutical Science College, Huai'an, P.R. China
| | - Dan McElheny
- Department of Chemistry, University of Illinois at Chicago, Chicago, IL, USA
| | | | - Karin Hauser
- Department of Chemistry, University of Konstanz, 78457, Konstanz, Germany
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11
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Minnes L, Greetham GM, Shaw DJ, Clark IP, Fritzsch R, Towrie M, Parker AW, Henry AJ, Taylor RJ, Hunt NT. Uncovering the Early Stages of Domain Melting in Calmodulin with Ultrafast Temperature-Jump Infrared Spectroscopy. J Phys Chem B 2019; 123:8733-8739. [PMID: 31557034 PMCID: PMC7007250 DOI: 10.1021/acs.jpcb.9b08870] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
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The signaling protein
calmodulin (CaM) undergoes a well-known change
in secondary structure upon binding Ca2+, but the structural
plasticity of the Ca2+-free apo state
is linked to CaM functionality. Variable temperature studies of apo-CaM indicate two structural transitions at 46 and 58
°C that are assigned to melting of the C- and N-terminal domains,
respectively, but the molecular mechanism of domain unfolding is unknown.
We report temperature-jump time-resolved infrared (IR) spectroscopy
experiments designed to target the first steps in the C-terminal domain
melting transition of human apo-CaM. A comparison
of the nonequilibrium relaxation of apo-CaM with
the more thermodynamically stable holo-CaM, with
4 equiv of Ca2+ bound, shows that domain melting of apo-CaM begins on microsecond time scales with α-helix
destabilization. These observations enable the assignment of previously
reported dynamics of CaM on hundreds of microsecond time scales to
thermally activated melting, producing a complete mechanism for thermal
unfolding of CaM.
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Affiliation(s)
- Lucy Minnes
- Department of Physics, SUPA , University of Strathclyde , Glasgow G4 0NG , United Kingdom
| | - Gregory M Greetham
- STFC Central Laser Facility, Research Complex at Harwell , Rutherford Appleton Laboratory , Harwell Campus , Didcot OX11 0QX , United Kingdom
| | | | - Ian P Clark
- STFC Central Laser Facility, Research Complex at Harwell , Rutherford Appleton Laboratory , Harwell Campus , Didcot OX11 0QX , United Kingdom
| | - Robby Fritzsch
- Department of Physics, SUPA , University of Strathclyde , Glasgow G4 0NG , United Kingdom
| | - Michael Towrie
- STFC Central Laser Facility, Research Complex at Harwell , Rutherford Appleton Laboratory , Harwell Campus , Didcot OX11 0QX , United Kingdom
| | - Anthony W Parker
- STFC Central Laser Facility, Research Complex at Harwell , Rutherford Appleton Laboratory , Harwell Campus , Didcot OX11 0QX , United Kingdom
| | | | | | - Neil T Hunt
- Department of Chemistry and York Biomedical Research Institute , University of York , Heslington, York YO10 5DD , United Kingdom
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12
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Ostrander JS, Lomont JP, Rich KL, Saraswat V, Feingold BR, Petti MK, Birdsall ER, Arnold MS, Zanni MT. Monolayer Sensitivity Enables a 2D IR Spectroscopic Immuno-biosensor for Studying Protein Structures: Application to Amyloid Polymorphs. J Phys Chem Lett 2019; 10:3836-3842. [PMID: 31246039 PMCID: PMC6823637 DOI: 10.1021/acs.jpclett.9b01267] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Immunosensors use antibodies to detect and quantify biomarkers of disease, though the sensors often lack structural information. We create a surface-sensitive two-dimensional infrared (2D IR) spectroscopic immunosensor for studying protein structures. We tether antibodies to a plasmonic surface, flow over a solution of amyloid proteins, and measure the 2D IR spectra. The 2D IR spectra provide a global assessment of antigen structure, and isotopically labeled proteins give residue-specific structural information. We report the 2D IR spectra of fibrils and monomers using a polyclonal antibody that targets human islet amyloid polypeptide (hIAPP). We observe two fibrillar polymorphs differing in their structure at the G24 residue, which supports the hypothesis that hIAPP polymorphs form from a common oligomeric intermediate. This work provides insight into the structure of hIAPP, establishes a new method for studying protein structures using 2D IR spectroscopy, and creates a spectroscopic immunoassay applicable for studying a wide range of biomarkers.
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Affiliation(s)
- Joshua S. Ostrander
- Department of Chemistry, University of Wisconsin—Madison, Madison, Wisconsin 53706, United States
| | - Justin P. Lomont
- Department of Chemistry, University of Wisconsin—Madison, Madison, Wisconsin 53706, United States
| | - Kacie L. Rich
- Department of Chemistry, University of Wisconsin—Madison, Madison, Wisconsin 53706, United States
| | - Vivek Saraswat
- Department of Materials Science and Engineering, University of Wisconsin—Madison, Madison, Wisconsin 53706, United States
| | - Benjamin R. Feingold
- Department of Materials Science and Engineering, University of Wisconsin—Madison, Madison, Wisconsin 53706, United States
| | - Megan K. Petti
- Department of Chemistry, University of Wisconsin—Madison, Madison, Wisconsin 53706, United States
| | - Erin R. Birdsall
- Department of Chemistry, University of Wisconsin—Madison, Madison, Wisconsin 53706, United States
| | - Michael S. Arnold
- Department of Materials Science and Engineering, University of Wisconsin—Madison, Madison, Wisconsin 53706, United States
| | - Martin T. Zanni
- Department of Chemistry, University of Wisconsin—Madison, Madison, Wisconsin 53706, United States
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13
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Oppermann M, Spekowius J, Bauer B, Pfister R, Chergui M, Helbing J. Broad-Band Ultraviolet CD Spectroscopy of Ultrafast Peptide Backbone Conformational Dynamics. J Phys Chem Lett 2019; 10:2700-2705. [PMID: 31059267 DOI: 10.1021/acs.jpclett.9b01253] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The far-UV spectral window widely used for the conformational analysis of biomolecules is not easily covered with broad-band lasers. This has made it difficult to use circular dichroism (CD) spectroscopy to directly follow fast structure changes. By combining transient CD spectroscopy in the deep-UV with thioamide substitution, we demonstrate a method to overcome this difficulty. We investigated a dipeptide whose two carbonyl oxygen atoms were replaced by sulfur, red-shifting the strong lowest-lying ππ* transitions into the more accessible 250-370 nm spectral window. Coupling of the two thioamide units cannot be resolved by achiral 2D-UV spectroscopy, but it gives rise to a pronounced bisignate CD spectrum. The transient CD spectra reveal weakening of this coupling in the electronically excited state, where conformational constraints are released. Our results show that direct local probing of fast backbone conformational change via CD spectroscopy is possible in combination with site-selective thio substitution in peptides and proteins.
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Affiliation(s)
- Malte Oppermann
- Laboratory of Ultrafast Spectroscopy, ISIC and Lausanne Centre for Ultrafast Science (LACUS) , École Polytechnique Fédérale de Lausanne , CH-1015 Lausanne , Switzerland
| | - Jasmin Spekowius
- Department of Chemistry , University of Zurich , Winterthurerstrasse 190 , CH-8057 Zürich , Switzerland
| | - Benjamin Bauer
- Laboratory of Ultrafast Spectroscopy, ISIC and Lausanne Centre for Ultrafast Science (LACUS) , École Polytechnique Fédérale de Lausanne , CH-1015 Lausanne , Switzerland
| | - Rolf Pfister
- Department of Chemistry , University of Zurich , Winterthurerstrasse 190 , CH-8057 Zürich , Switzerland
| | - Majed Chergui
- Laboratory of Ultrafast Spectroscopy, ISIC and Lausanne Centre for Ultrafast Science (LACUS) , École Polytechnique Fédérale de Lausanne , CH-1015 Lausanne , Switzerland
| | - Jan Helbing
- Department of Chemistry , University of Zurich , Winterthurerstrasse 190 , CH-8057 Zürich , Switzerland
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14
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Baronio CM, Baldassarre M, Barth A. Insight into the internal structure of amyloid-β oligomers by isotope-edited Fourier transform infrared spectroscopy. Phys Chem Chem Phys 2019; 21:8587-8597. [DOI: 10.1039/c9cp00717b] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Isotope-edited infrared spectroscopy reveals the structural unit of amyloid-β oligomers.
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Affiliation(s)
| | | | - Andreas Barth
- Department of Biochemistry and Biophysics
- Stockholm University
- Sweden
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