Research
Research in the Zanni group is aimed at exploring molecular structures and dynamics through vibrational motions and couplings. To accomplish this, sophisticated ultrafast multi-dimensional spectroscopies are being developed that correlate vibrational modes and measure frequency fluctuations. Emphasis is placed on understanding the molecular vibrations of complex biomolecules or materials to monitor their structures, dynamics and function.
Click on one of the following summaries for more information.
-
2D IR spectroscopy is a powerful technique for investigating molecular structures and dynamics. Using pair of pump pulses we "tag" the initial vibrational frequencies in the sample, and then use a probe pulse at some later time to monitor how they evolve. Information about dynamics is contained in 2D IR diagonal lineshapes, and information about molecular structures in diagonal peaks and cross-peaks. -
We developed a mid-IR pulse shaper which uses a germanium acousto-optic modulator (AOM) to manipulate the phase and amplitude of our mid-IR pump pulses. Using this shaper, we can control the time delay and phase of the pump pulses on a shot-to-shot basis, dramatically increasing the acquisition speed and the signal-to-noise of our 2D IR spectra, and enabling experiments requiring more complex pump pulses as well. -
We used isotope labeling and rapid-acquisition 2D IR to obtain real-time information about the kinetics of aggregation at specific residues within hIAPP. We showed folding is initiated in the turn region, followed by beta sheet formation. This is the most detailed information about the hIAPP aggregation pathway to date. -
We study molecules that inhibit amyloid formation in order to better understand how drugs might help fight amyloid diseases. We use 2D IR and residue-specific isotope labeling to obtain detailed structural information on amyloid-inhibitor complexes. We have found that the interactions in these complexes can be quite complex and evolve with time. -
2D IR linewidths are strongly sensitive to environment. By isotope-labeling individual residues within a membrane-bound peptide and monitoring the 2D IR linewidths of the isotope-labeled peak as a function of label location, we are able to probe the residue's location within the membrane and the peptide's structure on the membrane surface. -
We use transient IR, 2D IR, and transient 2D IR to study the structures and electron-transfer kinetics of rhenium-based dyes on TiO2 nanocrystalline films. 2D IR reveals that the dyes bind to the surface in multiple conformations, and transient 2D IR suggests that these conformations have radically different electron-transfer efficiencies. -
The Amide-I mode in the peptide backbone is strongly sensitive to peptide secondary structure. We use isotope-exchange processes and solid-phase peptide synthesis to insert 13C-18O labels into peptide backbones in precisely controlled locations, shifting the Amide I frequency to a less cluttered region of the IR spectrum. This allows us to study residue-specific structure and kinetics in small peptide aggregation processes. -
We built a mid-IR polarization shaper which can manipulate the polarization of our mid-IR pulses in addition to their amplitude and phase. Polarization shaping will allow us to disentangle overlapping responses in 2D IR spectra, greatly simplifying the interpretation of complex spectra.