Fig. 1.

Temperature-induced changes in HSP18.1 oligomerization. A nES mass spectra of HSP18.1 obtained at temperatures from 22 °C to 46 °C. At the lowest temperatures we observe HSP18.1 to exist almost exclusively as a 216 kDa dodecamer, with charge states centered around 6,350 m/z At higher temperatures monomers and dimers are observed at low m/z, and higher-order oligomers at high m/z, demonstrating the temperature-dependent dissociation and augmentation of the dodecamers. B A plot of the relative amount of HSP18.1 subunits existing in different oligomeric states shows that most of the HSP18.1 is redistributed from the dodecamers to high-order oligomers under heat-shock conditions. C Close examination of the abundance of the different species at 46 ° C shows a clear preference relative to a Gaussian distribution (p < 0.01) for oligomers with an even number of subunits. D Plots of the difference in free energy between a subunit free in solution or incorporated into either a dimer or dodecamer follow linear trends, suggesting that neither undergo significant structural change upon thermal activation. In all graphs the data and error bars represent the mean and standard deviation of three independent experiments.