Membrane-bound protein in giant vesicles: induced contraction and growth.

Cell-sized giant vesicles, produced by electroformation, were composed of phospholipids and zein (a hydrophobic protein that occupied a substantial percentage of the vesicle surface). Addition of sodium dodecyl sulfate removed the protein into the bulk phase, which led to a shrinkage of the vesicles. The vesicle bilayers were able to heal themselves from the damage caused by the departure of the zein, allowing the bilayers to maintain their spherical morphology.

Bolaforms with fourteen galactose units: a proposed site-directed cohesion of cancer cells.

[structure: see text] The multistep synthesis of a calixarene joined to a second calixarene via a long spacer is described. Since each calixarene bears multiple galactose-based units (known to bind strongly to rat hepatoma cells), there existed the possibility of cross-linking the cancer cells into a network. The compounds did not serve this purpose, a fact potentially correctable by adjusting or rigidifying the spacer.

Internally catalyzed separation of adhered lipid membranes.

When a giant vesicle composed of POPC (rendered anionic with 5 mol % POPG) touches a giant POPC vesicle (rendered cationic with 5 mol % of DDAB), the two vesicles adhere strongly. When, however, low levels (0.1-2 mol %) of a perylene-substituted lipid are incorporated in to the bilayer, the vesicles separate at a rate that depends on the additive concentration.

In-lens cryo-high resolution scanning electron microscopy: methodologies for molecular imaging of self-assembled organic hydrogels.

The micro- and nanoarchitectures of water-swollen hydrogels were routinely analyzed in three dimensions at very high resolution by two cryopreparation methods that provide stable low-temperature specimens for in-lens high magnification recordings. Gemini surfactants (gS), poly-N-isopropylacrylamides (p-NIP Am), and elastin-mimetic di- (db-E) and triblock (tb-E) copolymer proteins that form hydrogels have been routinely analyzed to the sub-10-nm level in a single day. After they were quench or high pressure frozen, samples in bulk planchets were subsequently chromium coated and observed at low temperature in an in-lens field emission SEM.

Migration of poly-L-lysine through a lipid bilayer.

When a giant vesicle, composed of neutral and anionic lipid (90:10 mol %), comes into contact with various poly-l-lysines (MW 500-29 300), ropelike structures form within the vesicle interior. By using fluorescence lipids and epi-fluorescence microscopy, we have shown that both neutral and anionic lipids are constituents of the ropes. Evidence that the ropes are also comprised of poly-l-lysine comes from two experiments: (a) direct microinjection of poly(acrylic acid) into rope-containing vesicles causes the ropes to contract into small particles, an observation consistent with a polycation/polyanion interaction; and (b) direct microinjection of fluorescein isothiocyanate (a compound that covalently labels poly-l-lysine with a fluorescent moiety) into rope-containing vesicles leads to fluorescent ropes.

Colloidal assemblies of branched geminis studied by cryo-etch-HRSEM. High-resolution scanning electron microscopy.

Cryo-etch-HRSEM is introduced as a useful method for exploring colloidal systems. The method fast freezes an aqueous sample (to -105 degrees C in 6-7 ms), removes some or all of the surface water by sublimation (etching), and magnifies the resulting colloidal structure by up to a million. Three new structurally similar gemini surfactants served to illustrate the technique.

Gemini-induced columnar jointing in vitreous ice. Cryo-HRSEM as a tool for discovering new colloidal morphologies.

A gemini surfactant is able to promote columnar jointing in vitreous ice where long pillars, often of hexagonal cross section, are formed. This jointing is visible by cryo-high-resolution scanning electron microscopy (cryo-HRSEM), in which colloidal suspensions in bulk water are cooled rapidly in liquid ethane, thereby avoiding the potential artifacts with other types of EM. The jointing is proposed to arise from a new type of colloidal morphology where the surfactant self-assembles into hexagonal columns.

Chemical Reaction between Colliding Vesicles.

An organic reaction between two populations of vesicles, one containing a nucleophile (blue) and the other an electrophile (red), was examined kinetically. By comparing the rates with those of suitable controls, it was demonstrated that the electrophile is transferred during vesicle collisions, and a fast intra-vesicular reaction ensues.