BIOIONS · Biological ions in the gas-phase: New techniques for structural characterization of isolated biomolecular ions

Recent intensive research on the laser spectroscopy of neutral gas-phase biomolecules has yielded a detailed picture of their structures and conformational preferences away from the complications of the bulk environment. In contrast, work on ionic systems has been sparse despite the fact that many important molecular groups are charged under physiological conditions. To address this probelm, we have developed a custom-built laser spectrometer, which incorporates a distincitive electrospray ionisation (ESI) cluster ion source, dedicated to producing biological anions (ATP,oligonucleotides) and their microsolvated clusters for structural characterization. Many previous laser spectrometers with ESI sources have suffered from producing hot" congested spectra as the ions were produced at ambient temperatures. This is a particularly serious limitation for spectroscopic studies of biomolecules, since these systems can possess high internal energies due tothe presence of numerous low frequency modes. Our spectrometer overcomes this problem by exploiting the newly developed physics technique of "buffer gas cooling" to produce cold ESI molecular ions. In this proposal, we now seek to exploit the new laser-spectrometer to perform detailed spectroscopic interrogations of ESI generated biomolecular anions and clusters. In addition to traditional ion-dissociation spectroscopies, we propose to develop two new laser spectroscopy techniques (Two-color tuneable IR spectroscopy and Dipole-bound excited state spectroscopy) to give the broadest possible structural characterizations of the systems of interest. Studies will focus on ATP/GTP-anions, olignonucleotides, and sulphated and carboxylated sugars. These methodologies will provide a general approach for performing temperature-controlled spectroscopic characterizations of isolated biological ions, with measurements on the corresponding micro-solvated clusters providing details of how the molecules are perturbed by solvent."