A Robust and Highly Permeable Outer Membrane Protein Pore Design for Potential Biomimetic Membrane Development

Precise chemical separations such as desalination and distillation are among the most challenging and resource intensive industrial process operations practiced today. Membrane separations offers advantages such as higher selectivity, simpler operation, and higher compactness over other separation processes. However, several challenges still remain in membrane materials design, particularly at the “pore” scale and translation of such designs to large areas necessary for application including: (1) Overcoming the trade-off between selectivity and permeability to develop membranes with high selectivity and permeability; (2) Designing subnanometer scale pores that result in the same subnanomter scale separations in synthesized membranes, which would be critical for the efficient small molecules (such as ions, gases and small organics) separation; (3) Synthesizing membranes with uniform pore size distributions. To meet these criteria, new materials, including carbon nanotubes, graphene oxide, and membrane proteins (and its mimics) have emerged as advanced membrane materials to assemble the desired pore geometry. However, designing sub-nm pores with perfectly monodisperse distributions is still an unmet challenge and no procedure exists to rationally design the continuum of pore sizes between 2 and 10 Å. In this talk, we will introduce a membrane protein design procedure along with molecular dynamics simulations to redesign the Outer membrane protein F (OmpF) and obtained an array of designs with varying pore sizes. Experimental results of representative mutants revealed a range of designs that an order of magnitude higher single channel water permeabilities comparing with classical aquaporins(~ 10⁹ water molecules/s) , while providing specific pore designs that exclude sucrose and larger solutes (>360 Da), glucose and larger solutes (>180 Da) or salt and larger solutes (>58 Da). This novel membrane protein pore design provided us the ability to develop membrane protein based biomimetic membrane with different subnanometer scale pore size, and applied for small molecule separations