The spectroscopy and dynamics of flexible biomolecules in the gas phase

The work presented in the volume focuses on understanding the complex potential energy landscapes of flexible biomolecules in the gas phase. Through a variety of double and triple resonance spectroscopic techniques, the structure and dynamics of flexible biomolecules can be elucidated and information about the connectivity and barriers to isomerization can be revealed. This work is presented in three main sections. The first focuses on the conformational preferences of two dipeptide mimetics: n-acetyltryptophan amide and n-acetyltryptophan methyl amide. It is found that two main conformational structures exist: an extended backbone C5 structure and a contracted backbone that has an intramolecular hydrogen bond between the amide groups. The effects of the conformation on the electronic spectroscopy of the molecules is also studied. It is found that the conformation of the backbone in both molecules has a dramatic effect on the ordering of the excited electronic states: 1Lb, 1La and 1πσ*. The second section focuses on the isomerization efficiency of melatonin in addition to the aforementioned species. Through the novel techniques of hole-filling spectroscopy and infrared induced population transfer spectroscopy isomerization quantum yields are determined. In the final section, hole-filling spectroscopy is used to study the vibrational cooling dynamics in a super-sonic expansion, and is coupled to stimulated-emission pumping as a means to probe the barriers to isomerization in the molecule tryptamine