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Kaufman LJ. Heterogeneity in Single-Molecule Observables in the Study of Supercooled Liquids. Annu Rev Phys Chem 2013; 64:177-200. [DOI: 10.1146/annurev-physchem-040412-110033] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Bulk approaches to studying heterogeneous systems obscure important details, as they report average behavior rather than the distribution of behaviors in such environments. Small-molecule and polymeric supercooled liquids, which display heterogeneity in their dynamics without an underlying structural heterogeneity that sets those dynamics, are important constituents of this category of condensed matter systems. A variety of approaches have been devised to unravel ensemble averaging in supercooled liquids. This review focuses on the ultimate subensemble approach, single-molecule measurements, as they have been applied to the study of supercooled liquids. We detail how three key experimental observables (single-molecule probe rotation, translation, and fluorescence lifetime) have been employed to provide detail on dynamic heterogeneity in supercooled liquids. Special attention is given to the potential for, but also the challenges in, discriminating spatial and temporal heterogeneity and detailing the length scales and timescales of heterogeneity in these systems.
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Affiliation(s)
- Laura J. Kaufman
- Department of Chemistry, Columbia University, New York, NY 10027
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Vallée RAL, Paul W, Binder K. Single Molecules Probing the Freezing of Polymer Melts: A Molecular Dynamics Study for Various Molecule-Chain Linkages. Macromolecules 2010. [DOI: 10.1021/ma101975j] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- R. A. L. Vallée
- Centre de Recherche Paul Pascal (CNRS), 115 avenue du docteur Albert Schweitzer, 33600 Pessac, France
| | - W. Paul
- Institut für Physik, Martin-Luther University, 06099 Halle, Germany
| | - K. Binder
- Institut für Physik, Johannes-Gutenberg University, 55099 Mainz, Germany
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Braeken E, De Cremer G, Marsal P, Pèpe G, Müllen K, Vallée RAL. Single Molecule Probing of the Local Segmental Relaxation Dynamics in Polymer above the Glass Transition Temperature. J Am Chem Soc 2009; 131:12201-10. [DOI: 10.1021/ja901636v] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Els Braeken
- Department of Chemistry and Institute of Nanoscale Physics and Chemistry, Katholieke Universiteit Leuven, Celestijnenlaan 200F, B-3001 Heverlee, Belgium, Centre Interdisciplinaire de Nanoscience de Marseille (UPR 3118, CNRS), Campus de Luminy, Case 913, F-13288 Marseille cedex 09, France, Max-Planck-Institut für Polymerforschnung, Ackermannweg 10, D-55128 Mainz, Germany, and Centre de Recherche Paul Pascal (UPR 8641, CNRS), 115 avenue du docteur Albert Schweitzer, F-33600 Pessac, France
| | - Gert De Cremer
- Department of Chemistry and Institute of Nanoscale Physics and Chemistry, Katholieke Universiteit Leuven, Celestijnenlaan 200F, B-3001 Heverlee, Belgium, Centre Interdisciplinaire de Nanoscience de Marseille (UPR 3118, CNRS), Campus de Luminy, Case 913, F-13288 Marseille cedex 09, France, Max-Planck-Institut für Polymerforschnung, Ackermannweg 10, D-55128 Mainz, Germany, and Centre de Recherche Paul Pascal (UPR 8641, CNRS), 115 avenue du docteur Albert Schweitzer, F-33600 Pessac, France
| | - Philippe Marsal
- Department of Chemistry and Institute of Nanoscale Physics and Chemistry, Katholieke Universiteit Leuven, Celestijnenlaan 200F, B-3001 Heverlee, Belgium, Centre Interdisciplinaire de Nanoscience de Marseille (UPR 3118, CNRS), Campus de Luminy, Case 913, F-13288 Marseille cedex 09, France, Max-Planck-Institut für Polymerforschnung, Ackermannweg 10, D-55128 Mainz, Germany, and Centre de Recherche Paul Pascal (UPR 8641, CNRS), 115 avenue du docteur Albert Schweitzer, F-33600 Pessac, France
| | - Gérard Pèpe
- Department of Chemistry and Institute of Nanoscale Physics and Chemistry, Katholieke Universiteit Leuven, Celestijnenlaan 200F, B-3001 Heverlee, Belgium, Centre Interdisciplinaire de Nanoscience de Marseille (UPR 3118, CNRS), Campus de Luminy, Case 913, F-13288 Marseille cedex 09, France, Max-Planck-Institut für Polymerforschnung, Ackermannweg 10, D-55128 Mainz, Germany, and Centre de Recherche Paul Pascal (UPR 8641, CNRS), 115 avenue du docteur Albert Schweitzer, F-33600 Pessac, France
| | - Klaus Müllen
- Department of Chemistry and Institute of Nanoscale Physics and Chemistry, Katholieke Universiteit Leuven, Celestijnenlaan 200F, B-3001 Heverlee, Belgium, Centre Interdisciplinaire de Nanoscience de Marseille (UPR 3118, CNRS), Campus de Luminy, Case 913, F-13288 Marseille cedex 09, France, Max-Planck-Institut für Polymerforschnung, Ackermannweg 10, D-55128 Mainz, Germany, and Centre de Recherche Paul Pascal (UPR 8641, CNRS), 115 avenue du docteur Albert Schweitzer, F-33600 Pessac, France
| | - Renaud A. L. Vallée
- Department of Chemistry and Institute of Nanoscale Physics and Chemistry, Katholieke Universiteit Leuven, Celestijnenlaan 200F, B-3001 Heverlee, Belgium, Centre Interdisciplinaire de Nanoscience de Marseille (UPR 3118, CNRS), Campus de Luminy, Case 913, F-13288 Marseille cedex 09, France, Max-Planck-Institut für Polymerforschnung, Ackermannweg 10, D-55128 Mainz, Germany, and Centre de Recherche Paul Pascal (UPR 8641, CNRS), 115 avenue du docteur Albert Schweitzer, F-33600 Pessac, France
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Prakash MK, Marcus RA. Dielectric dispersion interpretation of single enzyme dynamic disorder, spectral diffusion, and radiative fluorescence lifetime. J Phys Chem B 2007; 112:399-404. [PMID: 17956086 DOI: 10.1021/jp0758869] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A formulation based on measurable dielectric dispersion of enzymes is developed to estimate fluctuations in electrostatic interaction energy on time scales as long as milliseconds to seconds at a local site in enzymes. Several single molecule experimental obsevations occur on this time scale, currently unreachable by real time computational trajectory simulations. We compare the experimental results on the autocorrelation function of the fluctuations of catalysis rate with the calculations using the dielectric dispersion formulation. We also discuss the autocorrelation functions of the fluorescence lifetime and of spectral diffusion. We use a previously derived relation between the observables and the electric field fluctuations and calculate the latter using dielectric dispersion data for the proteins and the Onsager regression hypothesis.
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Affiliation(s)
- Meher K Prakash
- Noyes Laboratory of Chemical Physics MC 127-72, California Institute of Technology, Pasadena, CA 91125, USA
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Prakash MK, Marcus RA. An interpretation of fluctuations in enzyme catalysis rate, spectral diffusion, and radiative component of lifetimes in terms of electric field fluctuations. Proc Natl Acad Sci U S A 2007; 104:15982-7. [PMID: 17911244 PMCID: PMC2042148 DOI: 10.1073/pnas.0707859104] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Time-dependent fluctuations in the catalysis rate (deltak(t)) observed in single-enzyme experiments were found in a particular study to have an autocorrelation function decaying on the same time scale as that of spectral diffusion deltaomega(0)(t). To interpret this similarity, the present analysis focuses on a factor in enzyme catalysis, the local electrostatic interaction energy (E) at the active site and its effect on the activation free energy barrier. We consider the slow fluctuations of the electrostatic interaction energy (deltaE(t)) as a contributor to deltak(t) and relate the latter to deltaomega(0)(t). The resulting relation between deltak(t) and deltaomega(0)(t) is a dynamic analog of the solvatochromism used in interpreting solvent effects on organic reaction rates. The effect of the postulated deltaE(t) on fluctuations in the radiative component (deltagamma(r)(-1)(t)) of the fluorescence decay of chromophores in proteins also is examined, and a relation between deltagamma(r)(-1)(t) and deltaomega(0)(t) is obtained. Experimental tests will determine whether the correlation functions for deltak(t), deltaomega(0)(t), and deltagamma(r)(-1) are indeed similar for any enzyme. Measurements of dielectric dispersion, epsilon(omega), for the enzyme discussed elsewhere will provide further insight into the correlation function for deltaE(t). They also will determine whether fluctuations in the nonradiative component gamma(nr)(-1) of the lifetime decay has a different origin, fluctuations in distance for example.
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Affiliation(s)
- Meher K. Prakash
- Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, CA 91125
| | - R. A. Marcus
- Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, CA 91125
- *To whom correspondence should be addressed at:
Arthur Amos Noyes Professor of Chemistry, Noyes Laboratory of Chemical Physics, California Institute of Technology, 1200 East California Boulevard, MC 127-72, Pasadena, CA 91125. E-mail:
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Adhikari AN, Capurso NA, Bingemann D. Heterogeneous dynamics and dynamic heterogeneities at the glass transition probed with single molecule spectroscopy. J Chem Phys 2007; 127:114508. [PMID: 17887858 DOI: 10.1063/1.2768955] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
We studied the temperature dependence of the structural relaxation in poly(vinyl acetate) near the glass transition temperature with single molecule spectroscopy from Tg-1 K to Tg+12 K. The temperature dependence of the observed relaxation times matches results from bulk experiments; the observed relaxation times are, however, 80-fold slower than those from bulk experiments at the same temperature. We attribute this factor to the size of the probe molecule. The individual relaxation times of the single molecule environments are distributed normally on a logarithmic time scale, confirming that the dynamics in poly(vinyl acetate) is heterogeneous. The width of the distribution of individual relaxation times is essentially independent of temperature. The observed full width at half maximum (FWHM) on a logarithmic time axis is approximately 0.7, corresponding to a factor of about 5-fold, significantly narrower than the dielectric spectrum of the same material with a FWHM of about 2.0 on a logarithmic time axis, corresponding to a factor of about 100-fold. We explain this narrow width as the effect of temporal averaging of single molecule fluorescence signals over numerous environments due to a limited lifetime of the probed heterogeneities, indicating that heterogeneities are dynamic. We determine a loose upper limit for the ratio of the structural relaxation time to the lifetime of the heterogeneities (the rate memory parameter) of Q<80 for the range of investigated temperatures.
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Affiliation(s)
- Aashish N Adhikari
- Department of Chemistry, Williams College, 47 Lab Campus Drive, Williamstown, Massachusetts 01267, USA
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Vallée RAL, Baruah M, Hofkens J, De Schryver FC, Boens N, Van der Auweraer M, Beljonne D. Fluorescence lifetime fluctuations of single molecules probe the local environment of oligomers around the glass transition temperature. J Chem Phys 2007; 126:184902. [PMID: 17508827 DOI: 10.1063/1.2728902] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Single molecule fluorescence experiments have been performed on a BODIPY-based dye embedded in oligo(styrene) matrices to probe the density fluctuations and the relaxation dynamics of chain segments surrounding the dye molecules. The time-dependent fluorescence lifetime of the BODIPY probe was recorded as an observable for the local density fluctuations. At room temperature, the mean fraction of holes surrounding the probes is shown to be unaffected by the molecular weight in the glassy state. In contrast, the free volume increases significantly in the supercooled regime. These observations are discussed in the framework of the entropic theories of the glass transition.
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Affiliation(s)
- R A L Vallée
- Department of Chemistry and Institute of Nanoscale Physics and Chemistry (INPAC), Katholieke Universiteit Leuven, 3001 Heverlee, Belgium.
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Vallée RAL, Tomczak N, Vancso GJ, Kuipers L, van Hulst NF. Fluorescence lifetime fluctuations of single molecules probe local density fluctuations in disordered media: A bulk approach. J Chem Phys 2005; 122:114704. [PMID: 15836240 DOI: 10.1063/1.1861881] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We investigated the nanometer scale mobility of polymers in the glassy state by monitoring the dynamics of embedded single fluorophores. Recently we reported on fluorescence lifetime fluctuations which reflect the segmental rearrangement dynamics of the polymer in the surroundings of the single molecule probe. Here we focus on the nature of these fluorescence lifetime fluctuations. First the potential role of quenching and molecular conformational changes is discussed. Next we concentrate on the influence of the radiative density of states on the spontaneous emission of individual dye molecules embedded in a polymer. To this end we present a theory connecting the effective-medium theory to a cell-hole model, originating from the Simha-Somcynsky free-volume theory. The relation between the derived distributions of free volume and fluorescence lifetime allows one to determine the number of segments involved in the local rearrangement directly from experimental data. Results for two different polymers as a function of temperature are presented.
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Affiliation(s)
- R A L Vallée
- Applied Optics Group, MESA+ Institute for Nanotechnology, University of Twente, Enschede, The Netherlands.
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