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Abstract
Recent advances in ultrafast laser technology have spurred investigations of microheterogeneous solutions. In particular, researchers have explored details of reverse micelles (RMs), which present isolated droplets of polar solvent sequestered from a continuous nonpolar phase by a surfactant layer. This review explores recent studies utilizing a variety of ultrafast laser techniques to uncover details about structure and dynamics in various RMs. Using ultrafast vibrational spectroscopy, researchers have probed hydrogen-bond dynamics and vibrational energy relaxation in RMs. These studies have developed our understanding of reverse micellar structure, identifying varying water environments in the RMs. In a plethora of experiments employing probe molecules, researchers have explored the confined environment presented by RMs and their impact on a range of chemical reactions. These studies have shown that confinement, rather than the specific interactions with surfactants, is an important factor determining the impact of the reverse micellar environment on the chemistry.
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Affiliation(s)
- Nancy E Levinger
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, USA.
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Kondo M, Heisler IA, Conyard J, Rivett JPH, Meech SR. Reactive Dynamics in Confined Liquids: Interfacial Charge Effects on Ultrafast Torsional Dynamics in Water Nanodroplets. J Phys Chem B 2009; 113:1632-9. [DOI: 10.1021/jp808991g] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Minako Kondo
- School of Chemical Sciences and Pharmacy, University of East Anglia, Norwich NR4 7TJ, U.K
| | - Ismael A. Heisler
- School of Chemical Sciences and Pharmacy, University of East Anglia, Norwich NR4 7TJ, U.K
| | - Jamie Conyard
- School of Chemical Sciences and Pharmacy, University of East Anglia, Norwich NR4 7TJ, U.K
| | - Jasmine P. H. Rivett
- School of Chemical Sciences and Pharmacy, University of East Anglia, Norwich NR4 7TJ, U.K
| | - Stephen R. Meech
- School of Chemical Sciences and Pharmacy, University of East Anglia, Norwich NR4 7TJ, U.K
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Chieffo LR, Shattuck JT, Pinnick E, Amsden JJ, Hong MK, Wang F, Erramilli S, Ziegler LD. Nitrous Oxide Vibrational Energy Relaxation Is a Probe of Interfacial Water in Lipid Bilayers. J Phys Chem B 2008; 112:12776-82. [DOI: 10.1021/jp8012283] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Logan R. Chieffo
- Department of Chemistry, Department of Physics, Department of Biomedical Engineering and the Photonics Center, Boston University, 590 Commonwealth Avenue, Boston, MA 02215
| | - Jeffrey T. Shattuck
- Department of Chemistry, Department of Physics, Department of Biomedical Engineering and the Photonics Center, Boston University, 590 Commonwealth Avenue, Boston, MA 02215
| | - Eric Pinnick
- Department of Chemistry, Department of Physics, Department of Biomedical Engineering and the Photonics Center, Boston University, 590 Commonwealth Avenue, Boston, MA 02215
| | - Jason J. Amsden
- Department of Chemistry, Department of Physics, Department of Biomedical Engineering and the Photonics Center, Boston University, 590 Commonwealth Avenue, Boston, MA 02215
| | - M. K. Hong
- Department of Chemistry, Department of Physics, Department of Biomedical Engineering and the Photonics Center, Boston University, 590 Commonwealth Avenue, Boston, MA 02215
| | - Feng Wang
- Department of Chemistry, Department of Physics, Department of Biomedical Engineering and the Photonics Center, Boston University, 590 Commonwealth Avenue, Boston, MA 02215
| | - Shyamsunder Erramilli
- Department of Chemistry, Department of Physics, Department of Biomedical Engineering and the Photonics Center, Boston University, 590 Commonwealth Avenue, Boston, MA 02215
| | - Lawrence D. Ziegler
- Department of Chemistry, Department of Physics, Department of Biomedical Engineering and the Photonics Center, Boston University, 590 Commonwealth Avenue, Boston, MA 02215
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Karunakaran V, Pfaffe M, Ioffe I, Senyushkina T, Kovalenko SA, Mahrwald R, Fartzdinov V, Sklenar H, Ernsting NP. Solvation oscillations and excited-state dynamics of 2-amino- and 2-hydroxy-7-nitrofluorene and its 2'-deoxyriboside. J Phys Chem A 2008; 112:4294-307. [PMID: 18386856 DOI: 10.1021/jp712176m] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Push-pull substituted fluorenes are considered for use as dynamic solvation probes in polynucleotides. Their fluorescence band is predicted (by simulations) to show weak spectral oscillations on the subpicosecond time scale depending on the nucleotide sequence. The oscillations reflect the local far-infrared spectrum of the environment around the probe molecule. A connection is provided by the continuum theory of polar solvation which, however, neglects molecular aspects. We examine the latter using acetonitrile solution as a test case. A collective librational solvent mode at 100 cm(-1) is observed with 2-amino-7-nitrofluorene, 2-dimethylamino-7-nitrofluorene, 2-hydroxy-7-nitrofluorene, and its 2'-deoxyriboside. Different strengths of the oscillation indicate that rotational friction of nearby acetonitrile molecules depends on the solute structure or that H bonding is involved in launching the librational coherence. Polar solvation in methanol is used for comparison. With hydroxynitrofluorenes, the observation window is limited by intersystem crossing for which rates are reported. A prominent excited-state absorption band of nitrofluorenes at 430 nm can be used to monitor polar solvation. Structural and electronic relaxation pathways are discussed with the help of quantum chemical calculations.
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55
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Berg MA, Coleman RS, Murphy CJ. Nanoscale structure and dynamics of DNA. Phys Chem Chem Phys 2008; 10:1229-42. [DOI: 10.1039/b715272h] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Boyle-Roden E, Hoefer N, Dey KK, Grandinetti PJ, Caffrey M. High resolution 1H NMR of a lipid cubic phase using a solution NMR probe. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2007; 189:13-9. [PMID: 17855136 DOI: 10.1016/j.jmr.2007.08.010] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2007] [Revised: 08/08/2007] [Accepted: 08/11/2007] [Indexed: 05/17/2023]
Abstract
The cubic mesophase formed by monoacylglycerols and water is an important medium for the in meso crystallogenesis of membrane proteins. To investigate molecular level lipid and additive interactions within the cubic phase, a method was developed for improving the resolution of (1)H NMR spectra when using a conventional solution state NMR probe. Using this approach we obtained well-resolved J-coupling multiplets in the one-dimensional NMR spectrum of the cubic-Ia3d phase prepared with hydrated monoolein. A high resolution t-ROESY two-dimensional (1)H NMR spectrum of the cubic-Ia3d phase is also reported. Using this new methodology, we have investigated the interaction of two additive molecules, L-tryptophan and ruthenium-tris(2,2-bipyridyl) dichloride (rubipy), with the cubic mesophase. Based on the measured chemical shift differences when changing from an aqueous solution to the cubic phase, we conclude that L-tryptophan experiences specific interactions with the bilayer interface, whereas rubipy remains in the aqueous channels and does not associate with the lipid bilayer.
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Affiliation(s)
- E Boyle-Roden
- Department of Chemistry, The Ohio State University, 120 W. 18th Avenue, Columbus, OH 43210-1173, USA
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Qiu W, Wang L, Lu W, Boechler A, Sanders DAR, Zhong D. Dissection of complex protein dynamics in human thioredoxin. Proc Natl Acad Sci U S A 2007; 104:5366-71. [PMID: 17369362 PMCID: PMC1838516 DOI: 10.1073/pnas.0608498104] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2006] [Indexed: 11/18/2022] Open
Abstract
We report our direct study of complex protein dynamics in human thioredoxin by dissecting into elementary processes and determining their relevant time scales. By combining site-directed mutagenesis with femtosecond spectroscopy, we have distinguished four partly time-overlapped dynamical processes at the active site of thioredoxin. Using intrinsic tryptophan as a molecular probe and from mutation studies, we ascertained the negligible contribution to solvation by protein sidechains and observed that the hydration dynamics at the active site occur in 0.47-0.67 and 10.8-13.2 ps. With reduced and oxidized states, we determined the electron-transfer quenching dynamics between excited tryptophan and a nearby disulfide bond in 10-17.5 ps for three mutants. A robust dynamical process in 95-114 ps, present in both redox states and all mutants regardless of neighboring charged, polar, and hydrophobic residues around the probe, is attributed to the charge transfer reaction with its adjacent peptide bond. Site-directed mutations also revealed the electronic quenching dynamics by an aspartate residue at a hydrogen bond distance in 275-615 ps. The local rotational dynamics determined by the measurement of anisotropy changes with time unraveled a relatively rigid local configuration but implies that the protein fluctuates on the time scale of longer than nanoseconds. These results elucidate the temporal evolution of hydrating water motions, electron-transfer reactions, and local protein fluctuations at the active site, and show continuously synergistic dynamics of biological function over wide time scales.
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Affiliation(s)
- Weihong Qiu
- *Departments of Physics, Chemistry, and Biochemistry, Programs of Biophysics, Chemical Physics, and Biochemistry, Ohio State University, Columbus, OH 43210; and
| | - Lijuan Wang
- *Departments of Physics, Chemistry, and Biochemistry, Programs of Biophysics, Chemical Physics, and Biochemistry, Ohio State University, Columbus, OH 43210; and
| | - Wenyun Lu
- *Departments of Physics, Chemistry, and Biochemistry, Programs of Biophysics, Chemical Physics, and Biochemistry, Ohio State University, Columbus, OH 43210; and
| | - Amanda Boechler
- Department of Chemistry, University of Saskatchewan, Saskatoon, SK, Canada S7N 5C9
| | - David A. R. Sanders
- Department of Chemistry, University of Saskatchewan, Saskatoon, SK, Canada S7N 5C9
| | - Dongping Zhong
- *Departments of Physics, Chemistry, and Biochemistry, Programs of Biophysics, Chemical Physics, and Biochemistry, Ohio State University, Columbus, OH 43210; and
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Li T, Hassanali AA, Kao YT, Zhong D, Singer SJ. Hydration dynamics and time scales of coupled water-protein fluctuations. J Am Chem Soc 2007; 129:3376-82. [PMID: 17319669 DOI: 10.1021/ja0685957] [Citation(s) in RCA: 206] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We report experimental and theoretical studies on water and protein dynamics following photoexcitation of apomyoglobin. Using site-directed mutation and with femtosecond resolution, we experimentally observed relaxation dynamics with a biphasic distribution of time scales, 5 and 87 ps, around the site Trp7. Theoretical studies using both linear response and direct nonequilibrium molecular dynamics (MD) calculations reproduced the biphasic behavior. Further constrained MD simulations with either frozen protein or frozen water revealed the molecular mechanism of slow hydration processes and elucidated the role of protein fluctuations. Observation of slow water dynamics in MD simulations requires protein flexibility, regardless of whether the slow Stokes shift component results from the water or protein contribution. The initial dynamics in a few picoseconds represents fast local motions such as reorientations and translations of hydrating water molecules, followed by slow relaxation involving strongly coupled water-protein motions. We observed a transition from one isomeric protein configuration to another after 10 ns during our 30 ns ground-state simulation. For one isomer, the surface hydration energy dominates the slow component of the total relaxation energy. For the other isomer, the slow component is dominated by protein interactions with the chromophore. In both cases, coupled water-protein motion is shown to be necessary for observation of the slow dynamics. Such biologically important water-protein motions occur on tens of picoseconds. One significant discrepancy exists between theory and experiment, the large inertial relaxation predicted by simulations but clearly absent in experiment. Further improvements required in the theoretical model are discussed.
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Affiliation(s)
- Tanping Li
- Biophysics Program, The Ohio State University, Columbus, Ohio 43210, USA
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