1
|
Ress L, Malý P, Landgraf JB, Lindorfer D, Hofer M, Selby J, Lambert C, Renger T, Brixner T. Time-resolved circular dichroism of excitonic systems: theory and experiment on an exemplary squaraine polymer. Chem Sci 2023; 14:9328-9349. [PMID: 37712031 PMCID: PMC10498725 DOI: 10.1039/d3sc01674a] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Accepted: 07/28/2023] [Indexed: 09/16/2023] Open
Abstract
Experimental and theoretical foundations for femtosecond time-resolved circular dichroism (TRCD) spectroscopy of excitonic systems are presented. In this method, the system is pumped with linearly polarized light and the signal is defined as the difference between the transient absorption spectrum probed with left and with right circularly polarized light. We present a new experimental setup with a polarization grating as key element to generate circularly polarized pulses. Herein the positive (negative) first order of the diffracted light is left-(right-)circularly polarized and serves as a probe pulse in a TRCD experiment. The grating is capable of transferring ultrashort broadband pulses ranging from 470 nm to 720 nm into two separate beams with opposite ellipticity. By applying a specific chopping scheme we can switch between left and right circular polarizations and detect transient absorption (TA) and TRCD spectra on a shot-to-shot basis simultaneously. We perform experiments on a squaraine polymer, investigating excitonic dynamics, and we develop a general theory for TRCD experiments of excitonically coupled systems that we then apply to describe the experimental data in this particular example. At a magic angle of 54.7° between the pump-pulse polarization and the propagation direction of the probe pulse, the TRCD and TA signals become particularly simple to analyze, since the orientational average over random orientations of complexes factorizes into that of the interaction with the pump and the probe pulse, and the intrinsic electric quadrupole contributions to the TRCD signal average to zero for isotropic samples. Application of exciton theory to linear absorption and to linear circular dichroism spectra of squaraine polymers reveals the presence of two fractions of polymer conformations, a dominant helical conformation with close interpigment distances that are suggested to lead to short-range contributions to site energy shifts and excitonic couplings of the squaraine molecules, and a fraction of unfolded random coils. Theory demonstrates that TRCD spectra of selectively excited helices can resolve state populations that are practically invisible in TA spectroscopy due to the small dipole strength of these states. A qualitative interpretation of TRCD and TA spectra in the spectral window investigated experimentally is offered. The 1 ps time component found in these spectra is related to the slow part of exciton relaxation obtained between states of the helix in the low-energy half of the exciton manifold. The dominant 140 ps time constant reflects the decay of excited states to the electronic ground state.
Collapse
Affiliation(s)
- Lea Ress
- Institut für Physikalische und Theoretische Chemie, Universität Würzburg Am Hubland 97074 Würzburg Germany
| | - Pavel Malý
- Institut für Physikalische und Theoretische Chemie, Universität Würzburg Am Hubland 97074 Würzburg Germany
- Faculty of Mathematics and Physics, Charles University Ke Karlovu 5 121 16 Praha 2 Czech Republic
| | - Jann B Landgraf
- Institut für Physikalische und Theoretische Chemie, Universität Würzburg Am Hubland 97074 Würzburg Germany
- Freiburg Center for Interactive Materials and Bioinspired Technologies (FIT), Universität Freiburg Georges-Köhler-Allee 105 79110 Freiburg Germany
| | - Dominik Lindorfer
- Institut für Theoretische Physik, Johannes Kepler Universität Linz Altenberger Str. 69 4040 Linz Austria
| | - Michael Hofer
- Institut für Theoretische Physik, Johannes Kepler Universität Linz Altenberger Str. 69 4040 Linz Austria
| | - Joshua Selby
- Institut für Organische Chemie, Universität Würzburg Am Hubland 97074 Würzburg Germany
| | - Christoph Lambert
- Institut für Organische Chemie, Universität Würzburg Am Hubland 97074 Würzburg Germany
| | - Thomas Renger
- Institut für Theoretische Physik, Johannes Kepler Universität Linz Altenberger Str. 69 4040 Linz Austria
| | - Tobias Brixner
- Institut für Physikalische und Theoretische Chemie, Universität Würzburg Am Hubland 97074 Würzburg Germany
- Center for Nanosystems Chemistry (CNC), Universität Würzburg Theodor-Boveri-Weg 97074 Würzburg Germany
| |
Collapse
|
2
|
Andersen JH, Nanda KD, Krylov AI, Coriani S. Probing Molecular Chirality of Ground and Electronically Excited States in the UV-vis and X-ray Regimes: An EOM-CCSD Study. J Chem Theory Comput 2022; 18:1748-1764. [PMID: 35187935 DOI: 10.1021/acs.jctc.1c00937] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We present several strategies for computing electronic circular dichroism (CD) spectra across different frequency ranges at the equation-of-motion coupled-cluster singles and doubles level of theory. CD spectra of both ground and electronically excited states are discussed. For selected cases, the approach is compared with coupled-cluster linear response results as well as time-dependent density functional theory. The extension of the theory to include the effect of spin-orbit coupling is presented and illustrated by calculations of X-ray CD spectra at the L-edge.
Collapse
Affiliation(s)
- Josefine H Andersen
- DTU Chemistry, Technical University of Denmark, Kemitorvet Bldg 207, DK-2800 Kongens Lyngby, Denmark
| | - Kaushik D Nanda
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Anna I Krylov
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Sonia Coriani
- DTU Chemistry, Technical University of Denmark, Kemitorvet Bldg 207, DK-2800 Kongens Lyngby, Denmark
| |
Collapse
|
3
|
Morgenroth M, Scholz M, Cho MJ, Choi DH, Oum K, Lenzer T. Mapping the broadband circular dichroism of copolymer films with supramolecular chirality in time and space. Nat Commun 2022; 13:210. [PMID: 35017508 PMCID: PMC8752614 DOI: 10.1038/s41467-021-27886-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2021] [Accepted: 12/17/2021] [Indexed: 01/30/2023] Open
Abstract
Measurements of the electronic circular dichroism (CD) are highly sensitive to the absolute configuration and conformation of chiral molecules and supramolecular assemblies and have therefore found widespread application in the chemical and biological sciences. Here, we demonstrate an approach to simultaneously follow changes in the CD and absorption response of photoexcited systems over the ultraviolet-visible spectral range with 100 fs time resolution. We apply the concept to chiral polyfluorene copolymer thin films and track their electronic relaxation in detail. The transient CD signal stems from the supramolecular response of the system and provides information regarding the recovery of the electronic ground state. This allows for a quantification of singlet-singlet annihilation and charge-pair formation processes. Spatial mapping of chiral domains on femtosecond time scales with a resolution of 50 μm and diffraction-limited steady-state imaging of the circular dichroism and the circularly polarised luminescence (CPL) of the films is demonstrated.
Collapse
Affiliation(s)
- Marius Morgenroth
- Department Chemistry and Biology, Physical Chemistry 2, Faculty IV: School of Science and Technology, University of Siegen, Adolf-Reichwein-Str. 2, 57068, Siegen, Germany
| | - Mirko Scholz
- Department Chemistry and Biology, Physical Chemistry 2, Faculty IV: School of Science and Technology, University of Siegen, Adolf-Reichwein-Str. 2, 57068, Siegen, Germany
| | - Min Ju Cho
- Department of Chemistry, Research Institute for Natural Sciences, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul, 02841, Republic of Korea
| | - Dong Hoon Choi
- Department of Chemistry, Research Institute for Natural Sciences, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul, 02841, Republic of Korea
| | - Kawon Oum
- Department Chemistry and Biology, Physical Chemistry 2, Faculty IV: School of Science and Technology, University of Siegen, Adolf-Reichwein-Str. 2, 57068, Siegen, Germany.
| | - Thomas Lenzer
- Department Chemistry and Biology, Physical Chemistry 2, Faculty IV: School of Science and Technology, University of Siegen, Adolf-Reichwein-Str. 2, 57068, Siegen, Germany.
| |
Collapse
|
4
|
Hache F, Changenet P. Multiscale conformational dynamics probed by time-resolved circular dichroism from seconds to picoseconds. Chirality 2021; 33:747-757. [PMID: 34523161 DOI: 10.1002/chir.23359] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Revised: 08/27/2021] [Accepted: 08/28/2021] [Indexed: 01/08/2023]
Abstract
Time-resolved circular dichroism has been developed for a few decades to investigate rapid conformational changes in (bio)molecules. In our group, we have come up with several experimental set-ups allowing us to study pico-nanosecond local phenomena in molecular systems as well as much slower effects occurring in proteins and DNA in the folding processes. After an overview of the worldwide realizations in this domain, we present emblematic experiments that we have carried out, spanning time domain from picoseconds to seconds.
Collapse
Affiliation(s)
- François Hache
- Optics and Biosciences Laboratory, CNRS, INSERM, Ecole Polytechnique, Institut Polytechnique de Paris, Palaiseau, France
| | - Pascale Changenet
- Optics and Biosciences Laboratory, CNRS, INSERM, Ecole Polytechnique, Institut Polytechnique de Paris, Palaiseau, France
| |
Collapse
|
5
|
Scott M, Rehn DR, Norman P, Dreuw A. Ab Initio Excited-State Electronic Circular Dichroism Spectra Exploiting the Third-Order Algebraic-Diagrammatic Construction Scheme for the Polarization Propagator. J Phys Chem Lett 2021; 12:5132-5137. [PMID: 34030439 DOI: 10.1021/acs.jpclett.1c00839] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Excited-state rotatory strengths are reported for the first time at a correlated ab initio level, here with the algebraic diagrammatic construction scheme of the polarization propagator up to the third order. To demonstrate the capabilities of this computational approach, the gas phase S1 electronic circular dichroism spectra of the bicyclic ketones (1R)-camphor, (1R)-norcamphor, and (1R)-fenchone have been calculated at the ADC(3) level of theory. Furthermore, the solution excited-state spectra of the energetically lowest conformer of R-(+)-1,1'-bi(2-naphthol) have been computed with inclusion of a polarizable continuum model at the ADC(2) level of theory.
Collapse
Affiliation(s)
- Mikael Scott
- Interdisciplinary Center for Scientific Computing, Ruprecht-Karls University, Im Neuenheimer Feld 205, 69120 Heidelberg, Germany
| | - Dirk R Rehn
- Interdisciplinary Center for Scientific Computing, Ruprecht-Karls University, Im Neuenheimer Feld 205, 69120 Heidelberg, Germany
| | - Patrick Norman
- Department of Theoretical Chemistry and Biology, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, SE-106 91 Stockholm, Sweden
| | - Andreas Dreuw
- Interdisciplinary Center for Scientific Computing, Ruprecht-Karls University, Im Neuenheimer Feld 205, 69120 Heidelberg, Germany
| |
Collapse
|
6
|
Rogers DM, Jasim SB, Dyer NT, Auvray F, Réfrégiers M, Hirst JD. Electronic Circular Dichroism Spectroscopy of Proteins. Chem 2019. [DOI: 10.1016/j.chempr.2019.07.008] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
|
7
|
Scholz M, Morgenroth M, Cho MJ, Choi DH, Oum K, Lenzer T. Ultrafast Broadband Transient Absorption and Circular Dichroism Reveal Relaxation of a Chiral Copolymer. J Phys Chem Lett 2019; 10:5160-5166. [PMID: 31436421 DOI: 10.1021/acs.jpclett.9b02061] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
We present a study of the photoinduced dynamics of the chiral polyfluorene-phenylene copolymer PFPh in THF and in cholesteric thin films. After photoexcitation at 370 nm in THF, ultraviolet-visible-near-infrared (UV-vis-NIR) transient absorption spectra show fast subpicosecond to picosecond intrachain migration of singlet excitons, solvation dynamics, and an exciton lifetime of 410 ps. The PFPh thin film features also interchain singlet exciton migration and exhibits shorter (2.1 and 240 ps) and longer lifetime components (2800 ps, interchain recombination). Furthermore, a setup for ultrafast UV-vis broadband transient circular dichroism (TrCD) spectroscopy has been developed. Fast supramolecular relaxation processes are observed, which are linked to changes in the anisotropic polarizability and pitch length of the cholesteric film. Such combined ultrafast transient CD and absorption experiments hold promise to reveal not only details of relaxation processes in supramolecular arrangements but also structural rearrangements of chiral molecular systems featuring CD signals in the UV-vis region.
Collapse
Affiliation(s)
- Mirko Scholz
- Physical Chemistry, University of Siegen, Adolf-Reichwein-Str. 2, 57076 Siegen, Germany
| | - Marius Morgenroth
- Physical Chemistry, University of Siegen, Adolf-Reichwein-Str. 2, 57076 Siegen, Germany
| | - Min Ju Cho
- Department of Chemistry, Research Institute for Natural Sciences, Korea University, 5 Anam-dong, Sungbuk-gu, Seoul 136-701, Korea
| | - Dong Hoon Choi
- Department of Chemistry, Research Institute for Natural Sciences, Korea University, 5 Anam-dong, Sungbuk-gu, Seoul 136-701, Korea
| | - Kawon Oum
- Physical Chemistry, University of Siegen, Adolf-Reichwein-Str. 2, 57076 Siegen, Germany
| | - Thomas Lenzer
- Physical Chemistry, University of Siegen, Adolf-Reichwein-Str. 2, 57076 Siegen, Germany
| |
Collapse
|
8
|
Schmid M, Martinez-Fernandez L, Markovitsi D, Santoro F, Hache F, Improta R, Changenet P. Unveiling Excited-State Chirality of Binaphthols by Femtosecond Circular Dichroism and Quantum Chemical Calculations. J Phys Chem Lett 2019; 10:4089-4094. [PMID: 31260627 DOI: 10.1021/acs.jpclett.9b00948] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Time-resolved circular dichroism (TR-CD) is a powerful tool for probing conformational dynamics of biomolecules over large time scales that are crucial for establishing their structure-function relationship. However, such experiments, notably in the femtosecond regime, remain challenging due to their extremely weak signals, prone to polarization artifacts. By using binol and two bridged derivatives (PL1 and PL2) as chiral prototypes, we present here the first comprehensive study of this type in the middle UV, combining femtosecond TR-CD and quantum mechanical calculations (TD-DFT). We show that excitation of the three compounds induces large variations of their transient CD signals, in sharp contrast to those of their achiral transient absorption. We demonstrate that these variations arise from both the alteration of the electronic distribution and the dihedral angle in the excited state. These results highlight the great sensitivity of TR-CD detection to signals hardly accessible to achiral transient absorption.
Collapse
Affiliation(s)
- Marco Schmid
- Laboratoire d'Optique et Biosciences, CNRS, INSERM , Ecole Polytechnique, Institut Polytechnique de Paris , 91128 Palaiseau Cedex, France
| | - Lara Martinez-Fernandez
- LIDYL, CEA, CNRS , Université Paris-Saclay , F-91191 Gif-sur-Yvette , France
- Departamento de Química, Facultad de Ciencias, Modúlo13 , Universidad Autónoma de Madrid, Campus de Excelencia UAM-CSIC, Cantoblanco , 28049 Madrid , Spain
| | - Dimitra Markovitsi
- LIDYL, CEA, CNRS , Université Paris-Saclay , F-91191 Gif-sur-Yvette , France
| | - Fabrizio Santoro
- Consiglio Nazionale delle Ricerche , Istituto di Chimica dei Composti Organometallici, SS di Pisa, Area della Ricerca , via G. Moruzzi 1 , I-56124 Pisa , Italy
| | - François Hache
- Laboratoire d'Optique et Biosciences, CNRS, INSERM , Ecole Polytechnique, Institut Polytechnique de Paris , 91128 Palaiseau Cedex, France
| | - Roberto Improta
- LIDYL, CEA, CNRS , Université Paris-Saclay , F-91191 Gif-sur-Yvette , France
- Istituto Biostrutture e Bioimmagini , Consiglio Nazionale delle Ricerche , Via Mezzocannone 16 , I-80134 Napoli , Italy
| | - Pascale Changenet
- Laboratoire d'Optique et Biosciences, CNRS, INSERM , Ecole Polytechnique, Institut Polytechnique de Paris , 91128 Palaiseau Cedex, France
| |
Collapse
|
9
|
Stadnytskyi V, Orf GS, Blankenship RE, Savikhin S. Near shot-noise limited time-resolved circular dichroism pump-probe spectrometer. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2018; 89:033104. [PMID: 29604771 DOI: 10.1063/1.5009468] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We describe an optical near shot-noise limited time-resolved circular dichroism (TRCD) pump-probe spectrometer capable of reliably measuring circular dichroism signals in the order of μdeg with nanosecond time resolution. Such sensitivity is achieved through a modification of existing TRCD designs and introduction of a new data processing protocol that eliminates approximations that have caused substantial nonlinearities in past measurements and allows the measurement of absorption and circular dichroism transients simultaneously with a single pump pulse. The exceptional signal-to-noise ratio of the described setup makes the TRCD technique applicable to a large range of non-biological and biological systems. The spectrometer was used to record, for the first time, weak TRCD kinetics associated with the triplet state energy transfer in the photosynthetic Fenna-Matthews-Olson antenna pigment-protein complex.
Collapse
Affiliation(s)
- Valentyn Stadnytskyi
- Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana 47906, USA
| | - Gregory S Orf
- Departments of Biology and Chemistry, Photosynthetic Antenna Research Center, Washington University in St. Louis, St. Louis, Missouri 63130, USA
| | - Robert E Blankenship
- Departments of Biology and Chemistry, Photosynthetic Antenna Research Center, Washington University in St. Louis, St. Louis, Missouri 63130, USA
| | - Sergei Savikhin
- Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana 47906, USA
| |
Collapse
|
10
|
Hache F. Time-resolved circular dichroism: What can we learn on conformational changes? ACTA ACUST UNITED AC 2015. [DOI: 10.1117/12.2075705] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
|
11
|
Rüther A, Pfeifer M, Lórenz-Fonfría VA, Lüdeke S. Reaction Monitoring Using Mid-Infrared Laser-Based Vibrational Circular Dichroism. Chirality 2014; 26:490-6. [DOI: 10.1002/chir.22307] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2013] [Revised: 01/17/2014] [Accepted: 01/18/2014] [Indexed: 11/11/2022]
Affiliation(s)
- Anja Rüther
- Institute of Pharmaceutical Sciences; Albert-Ludwigs-Universität Freiburg; Freiburg Germany
| | - Marcel Pfeifer
- Fraunhofer Institute for Physical Measurement Techniques; Freiburg Germany
| | | | - Steffen Lüdeke
- Institute of Pharmaceutical Sciences; Albert-Ludwigs-Universität Freiburg; Freiburg Germany
| |
Collapse
|
12
|
Mendonça L, Hache F, Changenet-Barret P, Plaza P, Chosrowjan H, Taniguchi S, Imamoto Y. Ultrafast Carbonyl Motion of the Photoactive Yellow Protein Chromophore Probed by Femtosecond Circular Dichroism. J Am Chem Soc 2013; 135:14637-43. [DOI: 10.1021/ja404503q] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Lucille Mendonça
- Laboratoire d’Optique et Biosciences, Ecole Polytechnique/CNRS/INSERM, 91128 Palaiseau cedex, France
| | - François Hache
- Laboratoire d’Optique et Biosciences, Ecole Polytechnique/CNRS/INSERM, 91128 Palaiseau cedex, France
| | | | - Pascal Plaza
- Ecole Normale Supérieure,
Département de Chimie, UMR 8640 CNRS-ENS-UPMC, 24 rue Lhomond,
75005 Paris, France
| | - Haik Chosrowjan
- Institute for Laser Technology, 2-6 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Seiji Taniguchi
- Institute for Laser Technology, 2-6 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Yasushi Imamoto
- Department
of Biophysics, Graduate School of Sciences, Kyoto University, Kyoto 6068502, Japan
| |
Collapse
|
13
|
Rodriguez JJ, Mukamel S. Probing ring currents in Mg-porphyrins by pump-probe spectroscopy. J Phys Chem A 2012; 116:11095-100. [PMID: 22881200 PMCID: PMC3738187 DOI: 10.1021/jp3035874] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Theoretical studies of Manz et al. have shown that upon excitation of a Mg-porphyrin molecule with a circularly polarized laser pulse, a ring current can be generated that is much stronger than what can be induced by means of an external magnetic field with present technology. We show that the circular dichroism signal of a Mg-porphyrin molecule that has been excited to a state with an inner ring current is proportional to the magnitude of the probability of this ring current and can be used for the detection of this current. In analogy to magnetic circular dichroism, it probes the symmetry of degenerate excited states.
Collapse
Affiliation(s)
- Justo J Rodriguez
- Department of Chemistry, University of California, Irvine, California 92697, USA
| | | |
Collapse
|
14
|
Šanda F, Mukamel S. Novel coherent two-dimensional optical spectroscopy probes of chirality exchange and fluctuations in molecules. J Chem Phys 2011; 135:194201. [PMID: 22112074 DOI: 10.1063/1.3658277] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
We demonstrate how stochastic transitions between molecular configurations with opposite senses of chirality may be probed by 2D optical signals with specific pulse polarization configurations. The third-order optical response of molecular dimers (such as biphenyls) with dynamical axial chirality is calculated to order of k(2) in the wavevector of light. Spectroscopic signatures of equilibrium chirality fluctuations are predicted for three dynamical models (Ornstein-Uhlenbeck, two-state jump, and diffusion in double well) of the dihedral angle that controls the chirality.
Collapse
Affiliation(s)
- František Šanda
- Institute of Physics, Faculty of Mathematics and Physics, Charles University, Ke Karlovu 5, Prague, 121 16, Czech Republic.
| | | |
Collapse
|
15
|
Chen E, Goldbeck RA, Kliger DS. Nanosecond time-resolved polarization spectroscopies: tools for probing protein reaction mechanisms. Methods 2010; 52:3-11. [PMID: 20438842 PMCID: PMC2934884 DOI: 10.1016/j.ymeth.2010.04.015] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2010] [Revised: 04/26/2010] [Accepted: 04/27/2010] [Indexed: 11/25/2022] Open
Abstract
Polarization methods, introduced in the 1800s, offered one of the earliest ways to examine protein structure. Since then, many other structure-sensitive probes have been developed, but circular dichroism (CD) remains a powerful technique because of its versatility and the specificity of protein structural information that can be explored. With improvements in time resolution, from millisecond to picosecond CD measurements, it has proven to be an important tool for studying the mechanism of folding and function in many biomolecules. For example, nanosecond time-resolved CD (TRCD) studies of the sub-microsecond events of reduced cytochrome c folding have provided direct experimental evidence of kinetic heterogeneity, which is an inherent property of the diffusional nature of early folding dynamics on the energy landscape. In addition, TRCD has been applied to the study of many biochemical processes, such as ligand rebinding in hemoglobin and myoglobin and signaling state formation in photoactive yellow protein and prototropin 1 LOV2. The basic approach to TRCD has also been extended to include a repertoire of nanosecond polarization spectroscopies: optical rotatory dispersion (ORD), magnetic CD and ORD, and linear dichroism. This article will discuss the details of the polarization methods used in this laboratory, as well as the coupling of time-resolved ORD with the temperature-jump trigger so that protein folding can be studied in a larger number of proteins.
Collapse
Affiliation(s)
- Eefei Chen
- Department of Chemistry & Biochemistry University of California Santa Cruz Santa Cruz, California 95064
| | - Robert A. Goldbeck
- Department of Chemistry & Biochemistry University of California Santa Cruz Santa Cruz, California 95064
| | - David S. Kliger
- Department of Chemistry & Biochemistry University of California Santa Cruz Santa Cruz, California 95064
| |
Collapse
|
16
|
Thomas YG, Szundi I, Lewis JW, Kliger DS. Microsecond time-resolved circular dichroism of rhodopsin photointermediates. Biochemistry 2010; 48:12283-9. [PMID: 19905009 DOI: 10.1021/bi901657b] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Time-resolved circular dichroism measurements, over a spectral range from 300 to 700 nm, were made at delays of 5, 100, and 500 micros after room-temperature photoexcitation of bovine rhodopsin in a lauryl maltoside suspension. The purpose was to provide more structural information about intermediate states in the activation of rhodopsin and other G protein-coupled receptors. In particular, information was sought about photointermediates that are isochromic or nearly isochromic in their unpolarized absorbance. The circular dichroism spectrum of lumirhodopsin, obtained after correcting the 5 micros difference CD data for the bleached rhodopsin, was in reasonable agreement with the lumirhodopsin CD spectrum obtained previously by thermal trapping at -76 degrees C. Similarly, the metarhodopsin II spectrum obtained with a 500 micros delay was also in agreement with the results of previous work on the temperature-trapped form of metarhodopsin II. However, the CD of the mixture formed with a 100 micros delay after photoexcitation, whose only visible absorbing component is lumirhodopsin, could not be accounted for near 480 nm in terms of the initially formed, 5 micros lumirhodopsin CD spectrum. Thus, the CD spectrum of lumirhodopsin changes on the time scale from 5 to 100 micros, showing reduced rotational strength in its visible band, possibly associated with either a process responsible for a small spectral shift that occurs in the lumirhodopsin absorbance spectrum at earlier times or the Schiff base deprotonation-reprotonation which occurs during equilibration of lumirhodopsin with the Meta I(380) photointermediate. Either explanation suggests a chromophore conformation change closely associated with deprotonation which could be the earliest direct trigger of activation.
Collapse
Affiliation(s)
- Yiren Gu Thomas
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064, USA
| | | | | | | |
Collapse
|
17
|
Picosecond transient circular dichroism of the photoreceptor protein of the light-adapted form of Blepharisma japonicum. Chem Phys Lett 2009. [DOI: 10.1016/j.cplett.2009.10.059] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
|