The Aqueous Two Phase System (ATPS) Deserves Plausible Real-World Modeling for the Structure and Function of Living Cells

ABSTRACTAn aqueous two phase system (ATPS) is composed of binary hydrophilic polymers, for example, polyethylene glycol (PEG) and dextran, under an immiscible condition, and can also exhibit micro-segregation to produce cell-sized microcompartments like water-in-water microdroplets. Without membranes, interestingly, the microdroplet can serve as a micro-vessel (reactor) that contains various biochemical macromolecules like DNAs and proteins. We here present that PEG/dextran ATPS micro-segregation can provide an effective soft boundary to separate these biochemical macromolecules from the external environment. Trapped DNAs and proteins were concentrated inside such small spaces, and therefore, their interaction could be highly promoted to cause passive aggregation and controlled cross-linking if a certain cross-linker was added. We believe that the ATPS microdroplets might be associated with complicated structures and functions of living cells.