In mixtures of cetyltrimethylammonium bromide (CTAB) and sodium perfluorooctanoate (FC 7) in aqueous solution, novel bilayer cylinders with hemispherical end caps and open, flat discs coexist with spherical unilamellar vesicles, apparently at equilibrium. Such equilibrium among bilayer cylinders, spheres, and discs is only possible for systems with a spontaneous curvature, R o, and a positive Gaussian curvature modulus, . We have measured the size distributions of the spherical vesicles, cylinders, and discs by using cryo-electron microscopy; a simple analysis of this length distribution allows us to independently determine that the mean curvature modulus, Ϸ 5 ؎ 1 kBT and Ϸ 2 ؎ 1 kBT. This is one of the few situations in which R o, , and can be determined from the same experiment. From a similar analysis of the disk size distribution, we find that the edges of the discs are likely stabilized by excess CTAB. The fraction of discs, spherical vesicles, and cylinders depends on the CTAB͞FC 7 mole ratio: increasing CTAB favors discs, while decreasing CTAB favors cylinders. This control over aggregate shape with surfactant concentration may be useful for the design of templates for polymerization, mesoporous silicates, etc.cryogenic transmission electron microscopy ͉ surfactants ͉ vesicles T he starting point for the description of bilayer organization in solution is the harmonic approximation to the bending free energy (1):R 1 and R 2 are the principle radii of curvature of the structures, R o is the spontaneous radius of curvature, and are the mean and Gaussian curvature elastic constants, respectively, and A is the area of the bilayer membrane. The harmonic approximation is appropriate when the membrane thickness (1-3) [here Ϸ3 nm (4)] and the Debye length for ionic surfactants (2, 5, 6) [also Ϸ1-3 nm (4)] are small compared with R 1 and R 2 (Ϸ20-30 nm, see Fig. 1). The differences of the bending free energy, F B , of different aggregate geometries can often be of the order of k B T, leading to the possibility of multiple structures in equilibrium.The two elastic constants, and , play very different roles in determining bilayer organization. The magnitude of reflects the energy needed to bend the bilayer away from its spontaneous radius of curvature, R o . For ϳ k B T, thermal fluctuations give rise to significant curvature fluctuations, which lead to a net repulsive interaction between bilayers at short distances. This steric repulsion can stabilize unilamellar vesicles over multilamellar liposomes (3,4,7,8). Larger values of (ӷk B T), combined with a spontaneous curvature that picks out a particular vesicle radius, lead to unilamellar vesicles as the curvature variations inherent to multilamellar structures are energetically prohibited (3,4,9). A spontaneous bilayer curvature (1͞R o 0) is only possible when nonideal surfactant mixing causes the interior and exterior monolayers of the vesicle bilayer to have different compositions or environments (3, 10, 11).influences only the topology (and hence the number) of t...

Nanobiotechnology raises fascinating possibilities for new analytical assays in various fields such as bioelectronic assembly, biomechanics and sampling techniques, as well as in chips or micromachined devices. Recently, nanotechnology has greatly impacted biotechnological research with its potential applications in smart devices that can operate at the level of molecular manipulation. Micro total analysis system (micro-TAS) offers the potential for highly efficient, simultaneous analysis of a large number of biologically important molecules in genomic, proteomic and metabolic studies. This review aims to describe the present state-of-the-art of microsystems for use in biotechnological research, medicine and diagnostics.

Although recent progresses have unveiled the diverse in vivo functions of LKB1, detailed molecular mechanisms governing these processes still remain enigmatic. Here, we showed that Drosophila LKB1 negatively regulates organ growth by caspase-dependent apoptosis, without affecting cell size and cell cycle progression. Through genetic screening for LKB1 modifiers, we discovered the JNK pathway as a novel component of LKB1 signaling; the JNK pathway was activated by LKB1 and mediated the LKB1-dependent apoptosis. Consistently, LKB1-null mutant was defective in embryonic apoptosis and displayed a drastic hyperplasia in the central nervous system; these phenotypes were fully rescued by ectopic JNK activation as well as wild-type LKB1 expression. Furthermore, inhibition of LKB1 resulted in epithelial morphogenesis failure, which was associated with a decrease in JNK activity. Collectively, our studies unprecedentedly elucidate JNK as the downstream mediator of the LKB1-dependent apoptosis, and provide a new paradigm for understanding the diverse LKB1 functions in vivo.