If cell-free protein synthesis has been used, i.e. without living biological cells, this synthesis apparatus, e.g. an RNA-protein fusion such as that described by Roberts & Szostak (45) or a cell-free synthesis system as in Jermutus (44), can be encapsulated into particles such as liposomes or a water-in-oil emulsion, Tawfik and Griffiths (47), for generation of the gene product and sorting Polynu