title: Formation and vesiculation of biomembranes during spaceflight.
abstract: Shuttle flight, sounding rocket flight, and parabolic flight experiments demonstrate the formation of bilayer membrane vesicles (liposomes) in reduced gravity, following the dilution of detergent from detergent-phospholipid mixed micelles.  The reduction in detergent concentration initiates assembly of bilayer membrane sheets, which are sensitive to solution disturbances.  An increase in disturbances by forced dilution results in small diameter liposomes (< 150 nm), in both ground and flight samples.  In the absence of forced dilution, liposomes remain small at 1-g, but exhibit much larger diameters at 0-g (1000-2000 nm).  Our spaceflight data reveal that membrane assembly and vesiculation are strongly influenced by gravity-induced solution disturbances (e.g., convection currents), which limit vesicle diameter.
authors.affiliation: Division of Biology, NSCORT, Kansas State University, Manhattan 66506.
authors.forename: D E
authors.initials: DE
authors.lastname: Claassen
authors.forename: J S
authors.initials: JS
authors.lastname: van Twest
authors.forename: B S
authors.initials: BS
authors.lastname: Spooner
mesh_terms: D008081:Liposomes / Q000138:chemical synthesis* / Q000737:chemistry; D046911:Macromolecular Substances; D008560:Membrane Fluidity; D008563:Membrane Lipids / Q000138:chemical synthesis / Q000737:chemistry; D008567:Membranes, Artificial; D008823:Micelles; D010743:Phospholipids / Q000138:chemical synthesis / Q000737:chemistry; D013026:Space Flight; D014893:Weightlessness
chemical_list: D008081:Liposomes; D046911:Macromolecular Substances; D008563:Membrane Lipids; D008567:Membranes, Artificial; D008823:Micelles; D010743:Phospholipids