Additionally, could coacervate systems have somehow contributed to the emergence of a fatty acid-bound membrane as a mechanism to transition from membraneless to membrane-bound protocells? In particular, coacervate systems containing fatty acid monomers that can readily assemble and form a fatty acid membrane outside the coacervate when a specific pH or ionic strength is present have been developed. Other membraneless protocell models (in this case, a poly(ethylene glycol)-dextran aqueous two-phase system) have shown the capability to host fatty acid membranes as well. Further efforts have also been taken to study the plausibility of phospholipid-bound (which would have evolved from fatty acids at some point in the origin of life) membraneless compartments. In fact, "membranization" of coacervates, that has led to coacervates with non-lipid-based membranes, such as yeast cell wall fragments, is another avenue of current research relevant to understanding the emergence of membranes on early Earth. Therefore, although coacervates lack membranes, the conversion of membrane-free to membrane-bound compartmentalization could have occurred through the scaffolding of lipid-based membranes by a primitive coacervate-based "cytoplasm".