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Summary

In my laboratory, we use ultrashort bursts of light to trigger, then observe, rapid chemical and physical processes in solution. Our lasers can produce pulses less than 15 femtoseconds in duration, which is the time scale on which vibrational motions occur in molecules. We are studying a wide variety of chemical and biophysical properties of molecular dynamics and photo-reactivity in solution.

As we focus our femtosecond laser beams into a solution sample, we prepare excited electronic states of the molecules that absorb the laser, and launch coherent wave packets of vibrational energy. Using fluorescence, Raman, and absorption spectroscopy, we can track the evolution of the molecular dynamics and reactivity with greater time resolution than with any other technique. Thus, we can study some of the fastest known chemical reactions, as well as complex hydrogen-bonding phenomena that occur in aqueous solutions including proteins and DNA. To further understand and assign the ultrafast dynamics we observe in the femtosecond laser experiments, we use a variety of other techniques including steady-state spectroscopy, NMR experiments, and computational chemistry. Computational approaches rely on both electronic structure programs (such as Gaussian03) and molecular dynamics (GROMACS) and Monte Carlo classical force field calculations. With these, we can predict stable geometries, electrostatic properties (dipole moments and electric potentials), and vibrational spectra.

Current projects

Dynamics, Interactions, and Structure in Novel Room-Temperature Ionic Liquids
Probing supercooled liquid properties of non-aromatic molten salts by time-resolved fluorescence spectroscopy
OHD-RIKES as a probe of intermolecular dynamics and orientational relaxation
Anomalous transport in ionic liquids probed by NMR
Creation of novel ionic liquids with silicon-substituted cations
Comparative studies of ionic liquids and their homologous neutral binary solution analogs

Friction, Dynamics, and Microviscosity in Hydrophilic Polymers
Micelles, reverse micelles, and hydrogels of A-B-A triblock copolymers
Hydrogen bonds and intermolecular interactions in polymer solutions

Photo-induced Electron-Transfer in Condensed Phases and at Interfaces
Ultrafast charge separation in donor-bridge-acceptor systems

E. W. Castner, Jr., J. F. Wishart, and H. Shirota, "Intermolecular Dynamics, Interactions and Solvation in Ionic Liquids", Accounts of Chemical Research, 2007, 40(11), 1217-1227. doi: 10.1021/ar700169g

B. J. Lee, M. Barch, E. W. Castner, Jr., J. Völker, and K. J. Breslauer, "Structure and Dynamics in DNA looped Domains: CAG Triplet Repeat Sequence Dynamics Probed by 2-Aminopurine Fluorescence", Biochemistry, 2007, 46, 10756-10766. doi: 10.1021/bi7005674

J. F. Wishart and E. W. Castner, Jr., Editorial, ``The Physical Chemistry of Ionic Liquids'', J. Phys. Chem. B, 2007, 111(18), 4639-4640. doi: 10.1021/jp072262u. This editorial for the May 10, 2007 special issue of JPC B on the "Physical Chemistry of Ionic Liquids" was no. 14 on the Most-Accessed list for 2007.

S. H. Chung, R. Lopato, S. G. Greenbaum, H. Shirota, E. W. Castner, Jr., and J. F. Wishart, "A Nuclear Magnetic Resonance Study of the Dynamics of Imidazolium Ionic Liquids with -CH2Si(CH3)3 vs. -CH2C(CH3)3 substituents", J. Phys. Chem. B, 2007, 111(18), 4885-4893. doi: 10.1021/jp071755w

J. B. Issa, A. Salameh, E. W. Castner, Jr., J. F. Wishart, and S. S. Isied, "Conformational Analysis of the Electron Transfer Kinetics across Oligoproline Peptides Using N,N-dimethyl-1,4-benzenediamine Donors and Pyrene-1-sulfonyl Acceptors", J. Phys. Chem. B, 2007, 111, 6878-6886. doi: 10.1021/jp071599t

A. M. Funston, T. A. Fadeeva, J. F. Wishart, E. W. Castner Jr., "Fluorescence Probing of Temperature-Dependent Dynamics and Friction in Ionic Liquid Local Environments", J. Phys. Chem. B, 2007, 111(18), 4963-4977. doi: 10.1021/jp068298o. This paper was no. 9 on the Most-Cited Articles list for calendar 2007 (Mar. 31, 2008 data).

K. E. Steege, J. Wang, K. E. Uhrich, and E. W. Castner, Jr., "Local Polarity and Microviscosity in the Hydrophobic Cores of Amphiphilic Star-Like and Scorpion-Like Macromolecules", Macromolecules, 2007, 40(10), 3739-3748. doi: 10.1021/ma061779l

H. Shirota, J. F. Wishart, and E. W. Castner, Jr., "Intermolecular Interactions and Dynamics of Room Temperature Ionic Liquids That Have Silyl- and Siloxy-Substituted Imidazolium Cations", J. Phys. Chem. B, 2007, 111(18), 4819-4829. doi: 10.1021/jp067126o.

G. B. Shaw, C. D. Grant, H. Shirota, E. W. Castner Jr., G. J. Meyer, L. X. Chen, "Ultrafast Structural Rearrangements in the MLCT Excited State for Copper(I) bis-Phenanthrolines in Solution", J. Am. Chem. Soc., 2007, 129(7), 2147-2160. doi: 10.1021/ja067271f

H. Shirota and E. W. Castner, Jr., "Molecular Dynamics and Interactions in Aqueous and Dichloromethane Solutions of Polyvinylpyrrolidone", Journal of Chemical Physics, 125(3), 034904 (2006) (14 pages). doi: 10.1063/1.2208356

C. D. Grant, K. E. Steege, M. R. Bunagan, and E. W. Castner, Jr., "Microviscosity in Multiple Regions of Complex Aqueous Solutions of Poly(ethylene oxide) oxide)-poly(propylene oxide) oxide)-poly(ethylene oxide)", J. Phys. Chem. B, 2005, 109(47), 22273-22284. doi:10.1021/jp053929k

H. Shirota and E. W. Castner, Jr., "Why Are Viscosities Lower for Ionic Liquids with -CH2Si(CH3)3 vs.-CH2C(CH3)3 Substitutions on the Imidazolium Cations?", J. Phys. Chem. B, 2005 , 109(46), 21576-21585. doi:10.1021/jp053930j. This paper ranked no. 7 on the JPC B Hot Papers list, Sept. 2007.

H. Shirota and E. W. Castner, Jr., "Physical Properties and Intermolecular Dynamics of an Ionic Liquid Compared with its Isoelectronic Neutral Binary Solution", J. Phys. Chem. A, 2005, 109(42), 9388-9392. doi:10.1021/jp054664c This paper ranked no. 15 on the
JPC A Most-Accessed Articles list, Fall 2005.

E. M. Olano, C. D. Grant, T. J. Norman, Jr., E. W. Castner, Jr., and J. Z. Zhang, "Photoluminescence Decay Dynamics and Mechanism of Energy Transfer in Undoped and Mn2+ Doped ZnSe Nanoparticles", Journal of Nanoscience and Nanotechnology, 5(9), 1492-1497 (2005). doi:10.1166/jnn.2005.315

H. Shirota, A. M. Funston, J. F. Wishart, and E. W. Castner, Jr., "Ultrafast Dynamics of Pyrrolidinium Cation Ionic Liquids", Journal of Chemical Physics, 122(18), 184512 (2005) (12 pages). doi:10.1063/1.1893797

C. D. Grant, M. R. DeRitter, K. E. Steege, T. A. Fadeeva, and E. W. Castner, Jr., "Fluorescence Probing of Interior, Interfacial, and Exterior Regions in Solution Aggregates of Poly(ethylene oxide)-Poly(propylene oxide)-Poly(ethylene oxide) Triblock Copolymers", Langmuir, 2005, 21(5), 1745-1752. doi:10.1021/la047560m

E. W. Castner, Jr., review of J. Michael Hollas' "Modern Spectroscopy", 4th Edition, in J. Chem. Ed. (2005), 82(1), 43-44.

T. Ishida, P. J. Rossky, and E. W. Castner, Jr., "A Theoretical Investigation of the Shape and Hydration Properties of Aqueous Urea: Evidence for Nonplanar Urea Geometry", J. Phys. Chem. B, 2004,108(45), 17583-17590. doi:10.1021/jp0473218

Y. Sun, E. W. Castner Jr., C. L. Lawson, P. G. Falkowski, "Biophysical Characterization of Natural and Mutant Fluorescent Proteins Cloned from Zooxanthellate Corals", FEBS Letters 570 (2004) 175–183. doi:10.1016/j.febslet.2004.06.043

Alfred B. Roney, Brian Space, E. W. Castner, R. L. Napoleon and P. B. Moore, "A Molecular Dynamics Study of Aggregation Phenomena in Aqueous n-Propanol", J. Phys. Chem. B 2004, 108, 7389-7401. doi:10.1021/jp037922j

Alan K. Soper, Edward W. Castner, Jr., and Alenka Luzar, "Impact of Urea on Water Structure: a clue to its properties as a denaturant?", Biophysical Chemistry, 105, 649-666, 2003. doi:10.1016/S0301-4622(03)00095-4

R. J. Cave and E. W. Castner, Jr., “A Time-Dependent Density Functional Theory Investigation of the Ground and Excited States of Coumarins 102, 152, 153, and 343, J. Phys. Chem. A, 2002, 106, 12117-12123. doi:10.1021/jp026718d

R. J. Cave, K. Burke and E. W. Castner, Jr., "Theoretical Investigations of the Ground and Excited States of Coumarin 151 and Coumarin 120", J. Phys. chem. A, 2002, 106, 9294-9305. doi:10.1021/jp026071x

L. Frauchiger, H. Shirota, K. E. Uhrich, and E. W. Castner, Jr., "Dynamic Fluorescence Probing of the Local Environments within Amphiphilic Star-like Macromolecules", J. Phys. Chem. B, 2002, 106, 7463-7468. doi:10.1021/jp020746e

H. Shirota and E. W. Castner, Jr., "Ultrafast Dynamics in Aqueous Polymer Solutions: Polyacrylamide", J. Am. Chem. Soc., 2001, 123, 12877-12885. doi:10.1021/ja010290z

E. W. Castner, Jr., D. Kennedy, and R. J. Cave, "Solvent as Electron Donor: Donor/Acceptor Electronic Coupling Is a Dynamical Variable", J. Phys. Chem. A, 104 (13) 2869-2885 (2000). doi:10.1021/jp9936852 (cover picture for this issue!)