Structure and Dynamics of Biolmolecules in the Gas Phase Using Vibrationally and Rotationally Resolved Electronic Spectroscopy

Thomas, Jessica Anne (2011) Structure and Dynamics of Biolmolecules in the Gas Phase Using Vibrationally and Rotationally Resolved Electronic Spectroscopy. Doctoral Dissertation, University of Pittsburgh.

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Abstract

Rotationally resolved electronic spectroscopy is used to determine the rotational constants of small aromatic molecules. These rotational constants, when compared to calculated low energy structures, provide a precise description of the structure of the molecule. In addition, by comparing rotational constants for the structure in the ground and excited electronic states, as well as those associated with various vibronic transitions, an understanding of the dynamics of the molecule can be obtained. In this work, molecules containing double rings, including 1,3-benzodioxole, coumaran, and 1-phenylpyrrole, were studied using rotationally resolved electronic spectroscopy to determine their structures, low frequency vibrational motions, and changes in electronic distribution upon electronic excitation. Laser ablation, a technique used to produce gas phase samples of moderately sized biomolecules with significantly less decomposition than with thermal vaporization, was used to obtain gas phase samples of short peptide sequences. These molecules were studied using a IR/UV double resonance technique which enabled the collection of IR spectra with resolved transitions in the amide A and OH stretch regions. Specifically, several short sequences found in a folding nucleus of β-lactoglobulin were compared to calculated structures in order to identify intramolecular interactions that stabilize the structures.

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