Mass spectrometry analysis of in vitro Nuclear Aggregates of Polyamines

RATIONALE: In the nuclei of eukaryotic cells, polyamines and phosphate ions self-assemble via
ionic interactions and hydrogen bonding, generating three families of supramolecular compounds
that have been named large (l-), medium (m-) and small (s-) nuclear aggregates of polyamines
(NAPs). In a simulated nuclear environment, polyamines and phosphate ions generate the in vitro
NAPs (ivNAPs) that share strict structural and functional analogies with their cellular cognates.
Mass spectrometric data are expected to provide important structural details of NAPs/ivNAPs.
METHODS: We used both electrospray (ESI) and nitrocellulose (NC) matrix assisted laser
desorption ionization - time of flight (MALDI-TOF) mass spectrometry (MS) to support a variety
of analytical techniques previously addressed to structurally characterize NAPs/ivNAPs.
RESULTS: The dominant m/z values of s-ivNAP (m/z 735, 749, 761) are compatible with a defined
set of cyclic or linear aggregates. On the basis of the experimental molecular mass (a cluster centred
at m/z 2980), the m-ivNAP corresponds to the supramolecular assembly of 4 modules of s-ivNAPs.
No informative mass spectra were obtained for the l-ivNAP.
CONCLUSIONS: MS data support the models of NAPs that have been inferred by using an array
of analytical techniques. NC MALDI-MS contributed much more effectively than ESI-MS to the
structural characterization of ivNAPs.