This research aims to learn about ultrafast processes in molecules, ions, molecular aggregates and proteins by means of subpicosecond and picosecond laser methods. The work will focus on dynamical processes which include: vibrational energy relaxation in simple systems such as aqueous ions; vibrational energy transfer and partitioning in molecular aggregates; studies of the heating of molecules by laser excitation and the subsequent cooling pathways and dynamics; more precise and shorter timescale characterization of molecular motion of both ground and excited states in model condensed phase systems and of amino acid residues in proteins; and extensive studies of heme-ligand dynamics and cooperative effects in hemoglobin and related proteins using a variety of novel spectroscopic methods. The methods include: subpicosecond transient absorption spectroscopy; ultrafast (ca. 350 fs) fluorescence decays, anisotropies and spectra of amino acids, particularly tryptophans and tyrosines; picosecond transient Raman spectroscopy; a new approach to picosecond infrared spectroscopy; and nonlinear spectroscopies such as transient gratings and polarization methods. The goal of the hemeprotein experiments is to track the structural processes induced by ligand photodissociation into regions of the protein that are appropriately distant from the heme. In particular UV absorption, polarization spectra and subpicosecond fluorescence decays will be used to explore side chain responses to photodeligation. Fundamental questions concerning the effects of molecular motion on energy transfer will be addressed. Of particular interest is the study of ultrafast motions occurring in the nearly free rotation regime. The motional studies are brought into relation with theory by means of moleculary dynamics simulations.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
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Molecular and Cellular Biophysics Study Section (BBCA)
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University of Pennsylvania
Schools of Arts and Sciences
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Chuntonov, Lev; Pazos, Ileana M; Ma, Jianqiang et al. (2015) Kinetics of exchange between zero-, one-, and two-hydrogen-bonded states of methyl and ethyl acetate in methanol. J Phys Chem B 119:4512-20
Ghosh, Ayanjeet; Tucker, Matthew J; Gai, Feng (2014) 2D IR spectroscopy of histidine: probing side-chain structure and dynamics via backbone amide vibrations. J Phys Chem B 118:7799-805
Ma, Jianqiang; Pazos, Ileana M; Gai, Feng (2014) Microscopic insights into the protein-stabilizing effect of trimethylamine N-oxide (TMAO). Proc Natl Acad Sci U S A 111:8476-81
Ghosh, Ayanjeet; Wang, Jun; Moroz, Yurii S et al. (2014) 2D IR spectroscopy reveals the role of water in the binding of channel-blocking drugs to the influenza M2 channel. J Chem Phys 140:235105
Pazos, Ileana M; Ghosh, Ayanjeet; Tucker, Matthew J et al. (2014) Ester carbonyl vibration as a sensitive probe of protein local electric field. Angew Chem Int Ed Engl 53:6080-4
Ma, Jianqiang; Komatsu, Hiroaki; Kim, Yung Sam et al. (2013) Intrinsic structural heterogeneity and long-term maturation of amyloid ? peptide fibrils. ACS Chem Neurosci 4:1236-43
Singh, Prabhat K; Kuroda, Daniel G; Hochstrasser, Robin M (2013) An ion's perspective on the molecular motions of nanoconfined water: a two-dimensional infrared spectroscopy study. J Phys Chem B 117:9775-84
Kuroda, Daniel G; Abdo, Mohannad; Chuntonov, Lev et al. (2013) Vibrational dynamics of a non-degenerate ultrafast rotor: the (C12,C13)-oxalate ion. J Chem Phys 139:164514
Kuroda, Daniel G; Bauman, Joseph D; Challa, J Reddy et al. (2013) Snapshot of the equilibrium dynamics of a drug bound to HIV-1 reverse transcriptase. Nat Chem 5:174-81
Chuntonov, Lev; Kuroda, Daniel G; Ghosh, Ayanjeet et al. (2013) Quantum Beats and Coherence Decay in Degenerate States Split by Solvation. J Phys Chem Lett 4:1866-1871

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