Division into daughter vesicles can be induced either by mild

agitation or through the oxidation of thiol containing LDE225 compounds that interact with the membrane when oxidized [33•]. The fluid shear force division mechanism can go through multiple growth and division cycles through forces imparted by the environment. The latter thiol oxidation mechanism suggests that if a metabolic-like oxidation–reduction cycle were reconstituted within the vesicle, then multiple rounds of growth and division could be mediated by internal processes rather than by external forces. An alternative pathway developed by the Sugawara laboratory uses DNA replication to drive vesicle division. The lipid composition is more complex, including a mixture of natural and unnatural lipids plus a catalyst that converts precursor molecules into more lipid [34••]. During intravesicular DNA replication through PCR, ionic interactions between DNA and the membrane results in the division of the vesicle. Not only does this system couple two processes crucial for constructing cellular life, that is genomic replication

and compartment division, the molecular components used are compatible with biological Nutlin-3a price machinery, suggesting that cellular mimics that more closely resemble life as we know it could be built. However, the lipid composition of the membrane changes over the course of the reaction so that multiple rounds of division are not possible. There are now available many mechanisms for vesicle division that could be exploited for the construction of a cell. However, as noted above, the construction of a self-replicating system in the absence of other distinguishing features of life is unlikely to be perceived as living. A more convincing

cellular mimic would sense and Bcl-w respond to internal and external stimuli in order to coordinate different physiological processes and to adapt to changing environmental conditions. For example, natural cells ensure that division only occurs after genomic replication, and natural organisms adapt to fluctuating temperatures by modulating membrane compositions and protein chaperone levels. Interestingly, some of the environmental fluctuations that a cell must cope with arise from the cell itself, since living systems modify their environment by acquiring food and releasing waste. Although examples of in vitro constructed sense–response systems are few, recent developments suggest viable routes forward in exploiting sensory pathways for the building of cellular mimics. In vitro genetic systems can be constructed to sense and respond to the availability of small molecules. An in vitro cascading genetic network, for example, was built to control the production of protein in response to IPTG [ 35]. More recently, in vitro negative feedback loops exploiting tetracycline [ 36] and arabinose transcriptional repressors [ 37] were built.