All living cells use membranes to define physical boundaries and control the movement of biomolecules. Movement of molecules through membranes is a primary means of sending signals to and from cells.
Natural cells use enzymes to catalyze the biochemical reactions that manufacture their membranes from thioester precursors, but in this case Devaraj's team was able to get membranes to assemble spontaneously, without enzymes, through a process called native chemical ligation.