Biophysical and Materials Chemistry: Bottom-up Assembly of Synthetic Cells

We are developing a synthetic cytoplasm within lipid vesicles to enable reversible control of intracellular architecture. Our synthetic cytoplasm is comprised of aqueous polymer solutions that both mimic the crowded internal environment of living cells and are capable of phase separation to form two distinct and immiscible aqueous phases. Phase separation within living cells has been hypothesized as an explanation for the inhomogeneous distribution of many intracellular components not bounded by membranes. This phenomenon, referred to as microcompartmentation, is characteristic of living cells and is thought to have profound implications for cell function. Macromolecules are present in living cells at levels well above those required for phase separation in aqueous polymer solutions; the occurrence of phase separation would result in microcompartmentation, but has thus far been observed only in special cases such as eye lens cells.

Our experiments thus far suggest that aqueous phase separation is one viable mechanism for, and could contribute to, microcompartmentation in living cells. Further, they provide an experimental model system in which the mechanisms and functional significance of microcompartmentation for processes such as sequential enzymatic reactions, protein folding, and DNA condensation can be investigated.

Representative publications:

• “Aqueous phase separation in giant vesicles,” Helfrich, M. R.; Mangeney-Slavin, L. K.; Long, M. S.; Djoko, K. Y.; Keating, C. D. Journal of the American Chemical Society 2002, 124, 13374-13375.

• “Partitioning and assembly of metal nanoparticles and their bioconjugates in aqueous two-phase systems,” Helfrich, M. R.; El-Kouedi, M.; Etherton, M. R.; Keating, C. D. Langmuir 2005, 21, 8478-8486.

• “Dynamic microcompartmentation within synthetic cells,” Long, M. S.; Jones, C.; Helfrich, M. R.; Mangeney-Slavin, L. K.; Keating, C. D., Proc. Natl. Acad. Sci. USA, 2005, 102, 5920-5925.

• “Towards enzyme microcompartmentation in synthetic cells,” Long, M. S.; Helfrich, M. R.; Keating, C. D. Polymeric Materials: Science and Engineering 2005, 92, 554.

• “Nanoparticle conjugation increases protein partitioning in aqueous two-phase systems,” Long, M. S.; Keating, C. D. Analytical Chemistry 2006, 78, 379-386.