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Abstract
Optimization of pump-probe signal requires a complete understanding of how signal scales with experimental factors. In simple systems, signal scales quadratically with molar absorptivity, and linearly with fluence, concentration, and path length. In practice, scaling factors weaken beyond certain thresholds (e.g., OD > 0.1) due to asymptotic limits related to optical density, fluence and path length. While computational models can accurately account for subdued scaling, quantitative explanations often appear quite technical in the literature. This Perspective aims to present a simpler understanding of the subject with concise formulas for estimating absolute magnitudes of signal under both ordinary and asymptotic scaling conditions. This formulation may be more appealing for spectroscopists seeking rough estimates of signal or relative comparisons. We identify scaling dependencies of signal with respect to experimental parameters and discuss applications for improving signal under broad conditions. We also review other signal enhancement methods, such as local-oscillator attenuation and plasmonic enhancement, and discuss respective benefits and challenges regarding asymptotic limits that signal cannot exceed.
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Affiliation(s)
- Kevin C Robben
- Department of Chemistry, University of Iowa, Iowa City, Iowa 52242, USA
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2
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Wu Z, Xiong W. Neumann's principle based eigenvector approach for deriving non-vanishing tensor elements for nonlinear optics. J Chem Phys 2022; 157:134702. [PMID: 36209027 PMCID: PMC9531997 DOI: 10.1063/5.0118711] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2022] [Accepted: 09/05/2022] [Indexed: 11/14/2022] Open
Abstract
Physical properties are commonly represented by tensors, such as optical susceptibilities. The conventional approach of deriving non-vanishing tensor elements of symmetric systems relies on the intuitive consideration of positive/negative sign flipping after symmetry operations, which could be tedious and prone to miscalculation. Here, we present a matrix-based approach that gives a physical picture centered on Neumann's principle. The principle states that symmetries in geometric systems are adopted by their physical properties. We mathematically apply the principle to the tensor expressions and show a procedure with clear physical intuition to derive non-vanishing tensor elements based on eigensystems. The validity of the approach is demonstrated by examples of commonly known second and third-order nonlinear susceptibilities of chiral/achiral surfaces, together with complicated scenarios involving symmetries such as D6 and Oh symmetries. We then further applied this method to higher-rank tensors that are useful for 2D and high-order spectroscopy. We also extended our approach to derive nonlinear tensor elements with magnetization, which is critical for measuring spin polarization on surfaces for quantum information technologies. A Mathematica code based on this generalized approach is included that can be applied to any symmetry and higher order nonlinear processes.
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Affiliation(s)
- Zishan Wu
- Department of Chemistry and Biochemistry, UC San Diego, La Jolla, California 92093, USA
| | - Wei Xiong
- Authors to whom correspondence should be addressed: and
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3
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A polarization scheme that resolves cross-peaks with transient absorption and eliminates diagonal peaks in 2D spectroscopy. Proc Natl Acad Sci U S A 2022; 119:2117398119. [PMID: 35115405 PMCID: PMC8833161 DOI: 10.1073/pnas.2117398119] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/16/2021] [Indexed: 11/18/2022] Open
Abstract
Two-dimensional (2D) optical spectroscopy contains cross-peaks that are helpful features for determining molecular structure and monitoring energy transfer, but they can be difficult to resolve from the much more intense diagonal peaks. Transient absorption (TA) spectra contain transitions similar to cross-peaks in 2D spectroscopy, but in most cases they are obscured by the bleach and stimulated emission peaks. We report a polarization scheme, <0°,0°,+θ2(t2),-θ2(t2)>, that can be easily implemented in the pump-probe beam geometry, used most frequently in 2D and TA spectroscopy. This scheme removes the diagonal peaks in 2D spectroscopies and the intense bleach/stimulated emission peaks in TA spectroscopies, thereby resolving the cross-peak features. At zero pump-probe delay, θ2 = 60° destructively interferes two Feynman paths, eliminating all signals generated by field interactions with four parallel transition dipoles, and the intense diagonal and bleach/stimulated emission peaks. At later delay times, θ2(t2) is adjusted to compensate for anisotropy caused by rotational diffusion. When implemented with TA spectroscopy or microscopy, the pump-probe spectrum is dominated by the cross-peak features. The local oscillator is also attenuated, which enhances the signal two times. This overlooked polarization scheme reduces spectral congestion by eliminating diagonal peaks in 2D spectra and enables TA spectroscopy to measure similar information given by cross-peaks in 2D spectroscopy.
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4
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Limits in the Enhancement Factor in Near-Brewster Angle Reflection Pump-Probe Two-Dimensional Infrared Spectroscopy. CHINESE J CHEM PHYS 2022. [DOI: 10.1063/1674-0068/cjcp2111234] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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5
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Blackburn TJ, Tyler SM, Pemberton JE. Optical Spectroscopy of Surfaces, Interfaces, and Thin Films. Anal Chem 2022; 94:515-558. [DOI: 10.1021/acs.analchem.1c05323] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Thomas J. Blackburn
- Department of Chemistry and Biochemistry, University of Arizona, 1306 East University Boulevard, Tucson, Arizona 85721, United States
| | - Sarah M. Tyler
- Department of Chemistry and Biochemistry, University of Arizona, 1306 East University Boulevard, Tucson, Arizona 85721, United States
| | - Jeanne E. Pemberton
- Department of Chemistry and Biochemistry, University of Arizona, 1306 East University Boulevard, Tucson, Arizona 85721, United States
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6
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Lewis NHC, Tokmakoff A. Lineshape Distortions in Internal Reflection Two-Dimensional Infrared Spectroscopy: Tuning across the Critical Angle. J Phys Chem Lett 2021; 12:11843-11849. [PMID: 34871004 PMCID: PMC8686116 DOI: 10.1021/acs.jpclett.1c03432] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2021] [Accepted: 12/02/2021] [Indexed: 06/13/2023]
Abstract
Reflection mode two-dimensional infrared spectroscopy (R-2DIR) has recently emerged as a tool that expands the utility of ultrafast IR spectroscopy toward a broader class of materials. The impact of experimental configurations on the potential distortions of the transient reflectance (TR) spectra has not been fully explored, particularly in the vicinity of the critical angle θc and through the crossover from total internal reflection to partial reflection. Here we study the impact on the spectral lineshape of a dilute bulk solution as θc is varied across the incident angle by tuning the refractive index of the solvent. We demonstrate the significance of several distortions, including the appearance of phase twisted lineshapes and apparent changes in the spectral inhomogeneity, and show how these distortions impact the interpretation of the TR and R-2DIR spectroscopies.
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7
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Kübel J, Westenhoff S, Maj M. Giving voice to the weak: Application of active noise reduction in transient infrared spectroscopy. Chem Phys Lett 2021. [DOI: 10.1016/j.cplett.2021.139059] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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8
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Tiwari V. Multidimensional electronic spectroscopy in high-definition-Combining spectral, temporal, and spatial resolutions. J Chem Phys 2021; 154:230901. [PMID: 34241275 DOI: 10.1063/5.0052234] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Over the past two decades, coherent multidimensional spectroscopies have been implemented across the terahertz, infrared, visible, and ultraviolet regions of the electromagnetic spectrum. A combination of coherent excitation of several resonances with few-cycle pulses, and spectral decongestion along multiple spectral dimensions, has enabled new insights into wide ranging molecular scale phenomena, such as energy and charge delocalization in natural and artificial light-harvesting systems, hydrogen bonding dynamics in monolayers, and strong light-matter couplings in Fabry-Pérot cavities. However, measurements on ensembles have implied signal averaging over relevant details, such as morphological and energetic inhomogeneity, which are not rephased by the Fourier transform. Recent extension of these spectroscopies to provide diffraction-limited spatial resolution, while maintaining temporal and spectral information, has been exciting and has paved a way to address several challenging questions by going beyond ensemble averaging. The aim of this Perspective is to discuss the technological developments that have eventually enabled spatially resolved multidimensional electronic spectroscopies and highlight some of the very recent findings already made possible by introducing spatial resolution in a powerful spectroscopic tool.
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Affiliation(s)
- Vivek Tiwari
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore, Karnataka 560012, India
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9
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Baryiames CP, Garrett P, Baiz CR. Bursting the bubble: A molecular understanding of surfactant-water interfaces. J Chem Phys 2021; 154:170901. [PMID: 34241044 DOI: 10.1063/5.0047377] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Surfactant science has historically emphasized bulk, thermodynamic measurements to understand the microemulsion properties of greatest industrial significance, such as interfacial tensions, phase behavior, and thermal stability. Recently, interest in the molecular properties of surfactants has grown among the physical chemistry community. This has led to the application of cutting-edge spectroscopic methods and advanced simulations to understand the specific interactions that give rise to the previously studied bulk characteristics. In this Perspective, we catalog key findings that describe the surfactant-oil and surfactant-water interfaces in molecular detail. We emphasize the role of ultrafast spectroscopic methods, including two-dimensional infrared spectroscopy and sum-frequency-generation spectroscopy, in conjunction with molecular dynamics simulations, and the role these techniques have played in advancing our understanding of interfacial properties in surfactant microemulsions.
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Affiliation(s)
- Christopher P Baryiames
- Department of Chemistry, University of Texas at Austin, 105 E 24th St. Stop A5300, Austin, Texas 78712-1224, USA
| | - Paul Garrett
- Department of Chemistry, University of Texas at Austin, 105 E 24th St. Stop A5300, Austin, Texas 78712-1224, USA
| | - Carlos R Baiz
- Department of Chemistry, University of Texas at Austin, 105 E 24th St. Stop A5300, Austin, Texas 78712-1224, USA
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10
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Birdsall ER, Petti MK, Saraswat V, Ostrander JS, Arnold MS, Zanni MT. Structure Changes of a Membrane Polypeptide under an Applied Voltage Observed with Surface-Enhanced 2D IR Spectroscopy. J Phys Chem Lett 2021; 12:1786-1792. [PMID: 33576633 PMCID: PMC8162810 DOI: 10.1021/acs.jpclett.0c03706] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
The structures of many membrane-bound proteins and polypeptides depend on the membrane potential. However, spectroscopically studying their structures under an applied field is challenging, because a potential is difficult to generate across more than a few bilayers. We study the voltage-dependent structures of the membrane-bound polypeptide, alamethicin, using a spectroelectrochemical cell coated with a rough, gold film to create surface plasmons. The plasmons sufficiently enhance the 2D IR signal to measure a single bilayer. The film is also thick enough to conduct current and thereby apply a potential. The 2D IR spectra resolve features from both 310- and α-helical structures and cross-peaks connecting the two. We observe changes in the peak intensity, not their frequencies, upon applying a voltage. A similar change occurs with pH, which is known to alter the angle of alamethicin relative to the surface normal. The spectra are modeled using a vibrational exciton Hamiltonian, and the voltage-dependent spectra are consistent with a change in angle of the 310- and α-helices in the membrane from 55 to 44°and from 31 to 60°, respectively. The 310- and α-helices are coupled by approximately 10 cm-1. These experiments provide new structural information about alamethicin under a potential difference and demonstrate a technique that might be applied to voltage-gated membrane proteins and compared to molecular dynamics structures.
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Affiliation(s)
- Erin R Birdsall
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Megan K Petti
- 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
| | - Joshua S Ostrander
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
- Department of Chemistry, Indiana Wesleyan University, Marion, Indiana 46953, 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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11
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Petti MK, Ostrander JS, Birdsall ER, Kunz MB, Armstrong ZT, Alperstein AM, Zanni MT. A Proposed Method to Obtain Surface Specificity with Pump-Probe and 2D Spectroscopies. J Phys Chem A 2020; 124:3471-3483. [PMID: 32255629 PMCID: PMC7993518 DOI: 10.1021/acs.jpca.9b11791] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Surfaces and interfaces are ubiquitous in nature. From cell membranes, to photovoltaic thin films, surfaces have important function in both biological and materials systems. Spectroscopic techniques have been developed to probe systems like these, such as sum frequency generation (SFG) spectroscopies. The advantage of SFG spectroscopy, a second-order spectroscopy, is that it can distinguish between signals produced from molecules in the bulk versus on the surface. We propose a polarization scheme for third-order spectroscopy experiments, such as pump-probe and 2D spectroscopy, to select for surface signals and not bulk signals. This proposed polarization condition uses one pulse perpendicular compared to the other three to isolate cross-peaks arising from molecules with polar and uniaxial (i.e., biaxial) order at a surface, while removing the signal from bulk isotropic molecules. In this work, we focus on two of these cases: XXXY and YYYX, which differ by the sign of the cross-peak they create. We compare this technique to SFG spectroscopy and vibrational circular dichroism to provide insight to the behavior of the cross-peak signal. We propose that these singularly cross-polarized schemes provide odd-ordered spectroscopies the surface-specificity typically associated with even-ordered techniques.
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Affiliation(s)
- Megan K Petti
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Joshua S Ostrander
- 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
| | - Miriam Bohlmann Kunz
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Zachary T Armstrong
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Ariel M Alperstein
- Department of Chemistry, 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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12
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Ji Y, Yang X, Ji Z, Zhu L, Ma N, Chen D, Jia X, Tang J, Cao Y. DFT-Calculated IR Spectrum Amide I, II, and III Band Contributions of N-Methylacetamide Fine Components. ACS OMEGA 2020; 5:8572-8578. [PMID: 32337419 PMCID: PMC7178369 DOI: 10.1021/acsomega.9b04421] [Citation(s) in RCA: 184] [Impact Index Per Article: 46.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2019] [Accepted: 03/30/2020] [Indexed: 05/09/2023]
Abstract
The infrared spectrum (IR) characteristic peaks of amide I, amide II, and amide III bands are marked as amide or peptide characteristic peaks. Through the nuclear magnetic resonance study, N-methylacetamide has been determined to have six fine components, which include protonation, hydration, and hydroxy structures. Then the independent IR spectrum of every component in N-methylacetamide is calculated by using the density functional theory quantum chemistry method, and the contribution of each component to amide I, II, and III bands is analyzed. The results of this research can help to explain the formation of the amide infrared spectrum, which has positive significance in organic chemistry, analytical chemistry, and chemical biology.
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Affiliation(s)
- Yan Ji
- School
of Chemistry and Chemical Engineering, Henan
Normal University, Xinxiang 453007, China
| | - Xiaoliang Yang
- School
of Chemistry and Chemical Engineering, Nanjing
University, Nanjing 210000, China
| | - Zhi Ji
- School
of Chemistry and Chemical Engineering, Henan
Normal University, Xinxiang 453007, China
| | - Linhui Zhu
- College
of Chemical and Environmental Engineering, Shandong University of Science and Technology, Qingdao 266510, China
| | - Nana Ma
- School
of Chemistry and Chemical Engineering, Henan
Normal University, Xinxiang 453007, China
| | - Dejun Chen
- School
of Chemistry and Chemical Engineering, Henan
Normal University, Xinxiang 453007, China
| | - Xianbin Jia
- School
of Chemistry and Chemical Engineering, Henan
Normal University, Xinxiang 453007, China
| | - Junming Tang
- School
of Chemistry and Chemical Engineering, Henan
Normal University, Xinxiang 453007, China
| | - Yilin Cao
- School
of Chemistry and Chemical Engineering, Henan
Normal University, Xinxiang 453007, China
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13
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Ji Y, Yang X, Ji Z, Zhu L, Ma N, Chen D, Jia X, Tang J, Cao Y. DFT-Calculated IR Spectrum Amide I, II, and III Band Contributions of N-Methylacetamide Fine Components. ACS OMEGA 2020. [PMID: 32337419 DOI: 10.1021/acsomega.9b0442110.1021/acsomega.9b04421.s001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
The infrared spectrum (IR) characteristic peaks of amide I, amide II, and amide III bands are marked as amide or peptide characteristic peaks. Through the nuclear magnetic resonance study, N-methylacetamide has been determined to have six fine components, which include protonation, hydration, and hydroxy structures. Then the independent IR spectrum of every component in N-methylacetamide is calculated by using the density functional theory quantum chemistry method, and the contribution of each component to amide I, II, and III bands is analyzed. The results of this research can help to explain the formation of the amide infrared spectrum, which has positive significance in organic chemistry, analytical chemistry, and chemical biology.
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Affiliation(s)
- Yan Ji
- School of Chemistry and Chemical Engineering, Henan Normal University, Xinxiang 453007, China
| | - Xiaoliang Yang
- School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210000, China
| | - Zhi Ji
- School of Chemistry and Chemical Engineering, Henan Normal University, Xinxiang 453007, China
| | - Linhui Zhu
- College of Chemical and Environmental Engineering, Shandong University of Science and Technology, Qingdao 266510, China
| | - Nana Ma
- School of Chemistry and Chemical Engineering, Henan Normal University, Xinxiang 453007, China
| | - Dejun Chen
- School of Chemistry and Chemical Engineering, Henan Normal University, Xinxiang 453007, China
| | - Xianbin Jia
- School of Chemistry and Chemical Engineering, Henan Normal University, Xinxiang 453007, China
| | - Junming Tang
- School of Chemistry and Chemical Engineering, Henan Normal University, Xinxiang 453007, China
| | - Yilin Cao
- School of Chemistry and Chemical Engineering, Henan Normal University, Xinxiang 453007, China
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14
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Fritzsch R, Hume S, Minnes L, Baker MJ, Burley GA, Hunt NT. Two-dimensional infrared spectroscopy: an emerging analytical tool? Analyst 2020; 145:2014-2024. [PMID: 32051976 DOI: 10.1039/c9an02035g] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Ultrafast two-dimensional infrared (2D-IR) spectroscopy has provided valuable insights into biomolecular structure and dynamics, but recent progress in laser technology and data analysis methods have demonstrated the potential for high throughput 2D-IR measurements and analytical applications. Using 2D-IR as an analytical tool requires a different approach to data collection and analysis compared to pure research applications however and, in this review, we highlight progress towards usage of 2D-IR spectroscopy in areas relevant to biomedical, pharmaceutical and analytical molecular science. We summarise the technical and methodological advances made to date and discuss the challenges that still face 2D-IR spectroscopy as it attempts to transition from the state-of-the-art laser laboratory to the standard suite of analytical tools.
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Affiliation(s)
- Robby Fritzsch
- Department of Physics, SUPA, University of Strathclyde, Glasgow, G4 0NG, UK
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15
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Benderskii A, Morita A. Nonlinear spectroscopy and interfacial structure and dynamics. J Chem Phys 2019; 151:150401. [PMID: 31640380 DOI: 10.1063/1.5129103] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Alexander Benderskii
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
| | - Akihiro Morita
- Department of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
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16
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Mackin RT, Cohn B, Chuntonov L, Rubtsov IV. Intense-field interaction regime with weak laser pulses and localized plasmonic enhancement: Reference-free demonstration by 3rd- and 5th-order infrared spectroscopies. J Chem Phys 2019; 151:121103. [DOI: 10.1063/1.5120531] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Affiliation(s)
- Robert T. Mackin
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, USA
| | - Bar Cohn
- Schulich Faculty of Chemistry, and Solid State Institute, Technion, Haifa, Israel
| | - Lev Chuntonov
- Schulich Faculty of Chemistry, and Solid State Institute, Technion, Haifa, Israel
| | - Igor V. Rubtsov
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, USA
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17
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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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