Metastable liquid clusters in super- and undersaturated protein solutions.

Dense liquid phases, metastable with respect to a solid phase, but stable with respect to the solution, have been known to form in solutions of proteins and small-molecule substances. Here, with the protein lumazine synthase as a test system, using dynamic and static light scattering and atomic force microscopy, we demonstrate submicron size clusters of dense liquid. In contrast to the macroscopic dense liquid, these clusters are metastable not only with respect to the crystals, but also with respect to the low-concentration solution: the characteristic cluster lifetime is limited to approximately 10 s, after which they decay.

Determination of liposome size: a tool for protein reconstitution.

Reconstitution of proteins into liposomes is a widespread approach to analyzing their biological function. Many protocols exist for this procedure and for the subsequent analysis of proteins. Here, we establish a procedure for preparation and analysis of liposomes with a lipid composition reflecting the outer envelope of chloroplasts.

A metastable prerequisite for the growth of lumazine synthase crystals.

Dense liquid phases, metastable with respect to a solid phase, form in solutions of proteins and small-molecule materials. They have been shown to serve as a prerequisite for the nucleation of crystals and other ordered solid phases. Here, using crystals of the protein lumazine synthase from Bacillus subtilis, which grow by the generation and spreading of layers, we demonstrate that within a range of supersaturations the only mechanism of generation of growth layers involves the association of submicrometer-size droplets of the dense liquid to the crystal surface.