PACE has been instrumental in expanding the foundations for the creation of artificial cells.
PACE is not the first project to focus on creation of artificial cells that can begin to have life-like properties. Prior efforts include Luisi, Szostak, Noireaux and Libchaber. All these prior efforts, however, have been substantially based on chemical subsystems that have been taken directly from Nature. On one hand, this is to be expected, because Nature gives us our only example of life. On the other hand, restricting attention to Natural chemical subsystems may be limiting for a variety of reasons. One reason is that the chemical subsystems present in contemporary life are extremely evolved, to such an extent that they may not be able to exist in a living form without the full complement of all the chemical systems present in natural living cells. Simpler forms of life were undoubtedly present in the origins of life, but exactly what chemical subsystems were operative then are a matter of debate.
PACE has been the first project to expand the quest for artificial living cells from purely natural chemical subsystems to a wider arena including both novel chemical systems that are motivated not by their possible role in life as we know it, but rather by the pragmatic view that they may have needed properties for life yet to be engineered. Novel chemical subsystems not found in existing life, used in PACE, include informational molecules based on PNA, autocatalytic forms of DNA, and various synthetic lipids, all described in the section "Chemical substems for artificial cells".
Besides novel chemical subsystems, PACE has also broadened the arena to include technological components as possible parts of a living system, where technology may be used to provide functionalities to a system that are crucial to making it alive. This process of combining technology with chemical subsystems has been termed "complementation", since the technology is providing functionality that is complementary to that of the chemical systems. The main approach for complementation explored in PACE has been the development of microfluidic technology to provide complementary functionality, as described in the section on "Microfluidic support systems for artificial cells".
PACE has, in its broadening of the arena within which artificial cell science may be pursued, established new modalities for the programmability of living matter. No longer is the programming of life constrained to make modifications of the genetic code (the DNA) of existing organisms, as is the case with traditional synthetic biology approaches. Technological complementation gives several direct alternatives for programmability, in the design of the technology (e.s. configuration of the geometry of microfluidic devices) as well as the microprogramming of the devices. Another approach to programmability of artificial cell subsystems is the use of evolutionary optimization, as described in the section "Evolutionary optimization towards artificial cells".