Mass spectrometric 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 ionization (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 four 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.