The interior of living cells is both structurally and functionally organized.  Heterogeneity is maintained even in the absence of membranous boundaries such as those that surround organelles.  We are developing simple experimental models for cytoplasmic organization based on aqueous phase separation, which is a common phenomenon in crowded solutions of macromolecules.  When phases are present, solutes such as proteins or nucleic acids can be compartmentalized by partitioning into one of the phases, and the extent of localization can be controlled by compartment size.  Compartmentalization in aqueous phases can provide dramatic increases in reaction rates, for example nearly 70-fold rate enhancements for an RNA cleavage reaction. Aqueous two-phase systems can also be prepared inside cell-sized lipid vesicles by encapsulating both PEG and dextran polymers at several weight percent.  The resulting structures, where a lipid membrane surrounds two coexisting aqueous phases, are a primitive model of biological cells.

Experimental models for intracellular organization based on phase separation in aqueous polymer solutions

245th National Meeting (2013)

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