AutoCAD 2014

Infra Red Multiple Photon Spectroscopy

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Vibrational spectroscopy has been applied for decades as a powerful probe of polypeptide and protein secondary structures. The underlying assumption is that the function of biological molecules is related to the three-dimensional stucture. While linear infrared and Raman vibrational spectroscopies are well established and largely applied in the condensed phase, the past decade was witnessed the development of several experimental set-ups in order to probe the vibrational properties of polypeptides in the gas phase. For ionic molecules, an emerging gas phase technique at room temperature is based on action spectroscopy either using a messenger method (IR-PD infrared photon dissociation) or multiple photon dissociation (IR-MPD infrared multiple photon dissociation).

These techniques are based on the detection by mass spectrometry of ionic fragments that comes from the parent molecules upon (multiple) photon fragmentation processes.

With the growth in complexity of the biomolecules under scrutiny, with these new experimental set-ups, theoretical calculations have become more essential in order to understand the conformations that are responsible for the experimental spectroscopic fingerprints.

The most common approach has involved comparing IRMPD spectra to harmonic frequency calculations at the density-fuctional theory (DFT) level of theory. 

In collaboration with the group of Prof. Simonetta Fornarini and Prof. Maria Elisa Crestoni we are investigating the lowest energy equilibrium conformations for S-nitroso glutathione and S-nitroso cysteine. In order to answers as to which isomers can be responsible for the experimental vibrational signatures we are using a combination of classical Molecular Dynamics and Quantum Chemistry calculations.

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