Nanoflow electrospray mass spectrometry was used
to monitor the formation of protein heterodimers of HU
proteins from Bacillus stearothermophilus and
Bacillus subtilis. This has enabled us to analyze
both thermodynamic and kinetic features associated with
the dissociation of homodimeric HU proteins. The results
obtained correlate well with the kinetics of the protein
dissociation process and the free energy difference between
homo- and heterodimeric species anticipated from other
studies. We suggest that this approach will have general
applicability in studying protein association and dissociation
under near-equilibrium conditions and will be relevant
to a wide range of biological systems.