Fragmentation of proteins
using highly charged heavy ions
C. Ruehlicke*(a), Dieter Schneider(a),
Robert DuBois(c) , Rodney Balhorn(b)
This is an abstract
for a talk to be given at the
Fifth
Foresight Conference on Molecular Nanotechnology.
The full paper is now available.
Determining the sequence of amino acids in proteins is an
important step towards understanding the structure and function
of proteins. Currently not all proteins are accessible for
sequencing due to the limited availability of proteases, enzymes
that cleave proteins at specific amino acids. Therefore a need
for additional fragmentation methods exists. We are exploring the
fragmentation of proteins with highly charged heavy ions (HCI),
using ions extracted from the EBIT (electron beam ion trap)
facility at Livermore. The ions carry charges of up to 65+ (Au,
e.g.), which translate into potential energies comparable to the
kinetic energies of a few 100 keV, stressing electronic
interaction rather than collisional. In interaction studies with
surfaces HCI have been found to extract up to a few 100 electrons
per ion on approaching the surface. Oligopeptides deposited on a
solid substrate were used as a target on which the ions were
directed. Mass spectra of secondary ions ejected from the sample
were obtained using a time-of-flight spectrometer. We have
observed several processes, most notably the ejection of a series
of distinctive molecular fragments, characteristic for each
molecule. This indicates a specificity in the fragmentation
processes, where cleavage occurs preferably at certain molecular
sites. Intact molecule ejection also has been found to occur, as
well as the attachment of alkali or halogenide ions to molecules.
Besides fragmentation chemical alterations of the molecules are
possible due to the removal of binding electrons. The occurrence
of these processes is indicated by mass components exceeding the
intact molecule mass in the spectra.
Further studies are underway.
*Corresponding Address:
Christiane Ruehlicke, Lawrence Livermore National Laboratory,
Mail Stop: L-421, P.O. Box 808, Livermore, CA 94550, ph: (510)
423-7650, fax: (510) 422-5940, email: [email protected]
|