Ultrafast Optical Processes Laboratory

Ultrafast Optical Processes Laboratory

Research Emphasis

The resource develops laser-based methods for investigating structures, dynamics, structural changes, and ultrafast processes in biologically relevant samples. Available ultrafast (femtosecond, picosecond, and nanosecond) laser-based methodologies cover the whole spectral range from ultraviolet (UV) to infrared (IR). Phase-controlled IR pulse methods are used and further developed for multidimensional IR spectroscopy for structural and dynamical studies in peptides and proteins; transient spectroscopy (UV/VIS/IR) and multiphoton absorption techniques are used to study electron and energy transfer dynamics, photo-induced processes in light-sensitive biomolecules, and photophysics down to the single molecule level; time-correlated single-photon counting is used for fluorescence lifetime measurements; laser-induced temperature jumps are used to study protein-folding dynamics; and (time-resolved) confocal and total internal reflection fluorescence microscopy is used to study the diffusion and dynamics of single biomolecules and their complexes in various environments, including vesicles and cells.

Current Research

Two-dimensional IR spectroscopy (IR analogues of nuclear magnetic resonance) to study the dynamics of structures occurring in proteins and peptides; coherent IR methods to examine structural fluctuations through vibrational correlation functions; IR/VIS pump-probe methods with vibrational mode selectivity to study (vibrational) dynamics, mode coupling, and energy transfer; transient IR/VIS probing of protein folding and conformational dynamics through the application of T-jump, stopped-flow, and isotope-editing techniques; time- and frequency-resolved spectroscopy of single proteins and biological assemblies, including the application of lifetime imaging and fluorescence resonance energy transfer techniques in combination with confocal microscopy; and total internal reflection microscopy of single molecules in living cells and large lipid vesicles.

Resource Capabilities

Methods

Single/dual frequency two-dimensional/three-dimensional spectroscopy, pump-probe UV/VIS/IR spectroscopy, transient UV/VIS/IR spectroscopy, T-jump and stopped-flow protein-folding experiments, time-correlated single-photon counting, confocal microscopy (fluorescence correlation spectroscopy, photon trajectories, and lifetime imaging), and total internal reflection fluorescence microscopy.

Instruments

Instrumentation at the laboratory includes phase-controlled IR femtosecond pulses and tunable IR pulses; femtosecond to nanosecond fluorescence spectrometers; femtosecond to millisecond transient absorption spectrometers using Ti:Sapphire lasers; inverted confocal microscope with time-correlated single-photon counting, lifetime imaging, photon trajectory and multiphoton excitation capabilities; total internal reflection fluorescence microscope with fast charge-coupled device detector; femtosecond pulse excitation capabilities; rapid recording of fluorescence in the range of 100 fs to many ns by time-correlated photon counting and fluorescence upconversion methods; facilities for pump-probe experiments using all optical wavelengths available from optical parametric amplification; and T-jump apparatus with IR and UV/VIS probe wavelengths.

Software

Two-dimensional IR spectral calculations and fluorescence lifetime fitting.

Special Features

The laboratory has developed phase-controlled tunable IR pulses for multidimensional spectroscopy of peptides and small proteins. Transient absorption spectra at visible and IR wavelengths can be acquired in the fs to ms regime. Instrumentation has also been developed to perform transient spectroscopy with temperature jump initiation. Confocal and total internal reflection microscopes have been constructed for the investigation of single molecules, molecular assemblies, and protein folding. The Ultrafast Optical Processes Laboratory can accommodate essentially any laser-based experiment with emphasis on short pulsed methods. The staff is skilled in creating novel experimental configurations based on lasers needed for both short-term and long-term projects.

Publications

1. Hochstrasser, R. M., Dynamical models for two-dimensional infrared spectroscopy of peptides. Advances in Chemical Physics 132:1–56, 2006.
2. Krause, C. D., Lavnikova, N., Xie, J., Mei, E., Mirochnitchenko, O. V., Jia, Y., Hochstrasser, R. M., et al., Preassembly and ligand-induced restructuring of the chains of the INF-gamma receptor complex: The roles of Jak kinases, Stat1 and the receptor chains. Cell Research 16:55–69, 2006.
3. Kim, Y.-S. and Hochstrasser, R. M., Chemical exchange 2D IR of hydrogen-bond making and breaking. Proceedings of the National Academy of Sciences USA 102:11185–11190, 2005.
4. Fang, C. and Hochstrasser, R. M., Two-dimensional infrared spectra of the 13C=18O isotopomers of alanine residues in an alpha-helix. Journal of Physical Chemistry B 109:18652–18663, 2005.