In an effort to understand the vast complexity of the underlying processes within a cell at
a molecular level, the first step lies in revealing the fundamental physical and chemical
properties, as well as the structure, of biopolymers (proteins and DNA). With the
development of modern experimental techniques it has become possible to study these
large molecules under well-defined conditions in the gas phase, by closely inspecting
their interactions with energetic photons and electrons.
In this Thesis, we present the experimental setups for the action spectroscopy of peptides,
proteins and nucleotides, as well as the hydrated complexes (hydrated nucleotides), in the
gas phase. We present the details and the operation of the two experimental setups based
on coupling the linear quadrupole ion trap with: (1) a VUV or a soft X-ray synchrotron
beamline and (2) a focusing electron gun.
In the case (1), the existing experimental setup consisting of a commercial quadrupole
ion trap mass spectrometer (LTQ XL from Thermo Scientific), equipped with an
electrospray ion source, was coupled to the VUV beamline DESIRS and the soft X-ray
beamline PLEIADES at the synchrotron SOLEIL (France). The setups were used to study
the photo-induced ionization/fragmentation of trapped biopolymers and nanosolvated
species. The results obtained with this setups include VUV action spectroscopy of
protonated Leucine-Enkephalin peptide (both a monomer and a dimer) and a
nanosolvated nucleotide Adenosine monophosphate (AMP), in (5-15) eV photon energy
range. The inner-shell action spectroscopy in the soft X-ray energy range (around C and
N K-edge), was performed for multiply charged precursor of Ubiquitin protein. The
photo-dissociation and photo-fragmentation ion yields for several fragment ions from all
above mentioned macromolecules were extracted and the obtained spectral features were
discussed considering relevant photon-induced processes.
In the case (2), new experimental setup was developed by coupling the same LTQ XL
ion trap with a focusing electron gun, in order to perform an electron activation tandem
mass spectrometry, as well as an electron-impact action spectroscopy of trapped
biopolymer ions. The ion optic simulations using SIMION program were performed in
order to investigate the propagation of the electron beam in the RF+DC ion trap. Tests
measurements for electron-induced fragmentation of Substance P, Melittin and Ubiquitin
are presented for the impact energy of 300 eV. Finally, we present the electron-impact
inner-shell action spectroscopy of the multiply charged Ubiquitin protein, in the vicinity
of C K-edge energies of (280-300) eV. The electron-impact results are compared with the
soft X-ray photon-impact action spectroscopy results obtained for the same target.
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