  We report that protein confinement within nanoscopic vesicular compartments
corresponds to a liquid-liquid phase transition with the protein/water within
vesicle lumen interacting very differently than in bulk. We show this effect
leads to considerable structural changes on the proteins with evidence
suggesting non-alpha helical conformations. Most importantly both aspects lead
to a significant improvement on protein stability against thermal denaturation
up to 95degC at neutral pH, with little or no evidence of unfolding or reduced
enzymatic activity. The latter parameter does indeed exhibit an increase after
thermal cycling. Our results suggest that nanoscopic confinement is a promising
new avenue for the enhanced long-term storage of proteins. Moreover, our
investigations have potentially important implications for the origin of life,
since such compartmentalization may well have been critical for ensuring the
preservation of primordial functional proteins under relatively harsh
conditions, thus playing a key role in the subsequent emergence of primitive
life forms.
