Spontaneous transformation from micelles to vesicles associated with sequential conversions of comprising amphiphiles within assemblies.

A morphological transformation from hybrid micelles to giant vesicles was observed in aqueous dispersion associated with formation of a double-chained amphiphile as a result of the migration of dodecylamine from the amphiphilic imine to the amphiphilic aldehyde within the hydrophobic environment of amphiphilic aggregates.

Autocatalytic membrane-amplification on a pre-existing vesicular surface.

In water, phosphoric membrane molecule (V(-)) self-assembled to form an anionic giant vesicle, the surface of which served as a catalyst for the autocatalytic formation of V(-) from its membrane precursor (V*), and the amplified V(-) produced a new vesicle using the original vesicle as a scaffold.

Population study of sizes and components of self-reproducing giant multilamellar vesicles.

Population analysis of a system of self-reproducing giant multilamellar vesicles (GMVs) was carried out by means of flow cytometry. The multidimensional distribution of forward light scattering (FS), side light scattering (SS), and fluorescence (FL) intensities originating from each GMV provided information about changes in a population composed of 104 vesicles. FS-FL dot plots indicated that, after the addition of the membrane precursor, the size distribution of the newly generated vesicles was nearly the same as that of the original, but the catalyst content was reduced. This result can be interpreted as evidence for the occurrence of the self-reproduction of GMVs. Moreover, the new GMVs recovered the amount of catalyst to the initial value, keeping their size distribution constant, when a solution of the catalyst was added to the new GMVs. These results are the first experimental evidence for a novel phenomenon on GMV size distribution during their self-reproducing cycle.

Fluorescence microscopic investigation on morphological changes of giant multilamellar vesicles induced by amphiphilic additives.

Adding an artificial bolaamphiphile to a dispersion of giant multilamellar vesicles (GMVs) made of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylcholine (POPC) induced a cup-shaped deformation in GMVs accompanied by partial extrusion of the inner vesicle; thereafter, the deformed vesicles returned to their original shape. On the other hand, when the artificial bolaamphiphile together with a surfactant was added to the vesicular dispersion, these deformation and reformation dynamics were transmitted from the outer membranes in GMVs to the inner membranes until an intact inner vesicle was extruded out of the outer membrane. The microscopic aspects of these processes were investigated using amphiphiles tagged with individual fluorophores.

Membrane dynamics of a myelin-like giant multilamellar vesicle applicable to a self-reproducing system.

A real time observation of a myelin-like giant multilamellar vesicle (mGMV) revealed that it divided into relatively small mGMVs when an aqueous solution of an electrolyte was added. Furthermore, the mGMV showed a division process accompanied by the growth of the dividing mGMVs when a bolaamphiphile which was composed of an electrolyte unit and a vesicular amphiphile unit was added. This vesicular system can be regarded as a self-reproduction of mGMV, where the added amphiphile acts as a supplier of both the vesicular amphiphile and the division initiator.

A novel system of self-reproducing giant vesicles.

Novel self-reproducing giant vesicles, consisting of a vesicular amphiphile with an imine group in its hydrophobic chain, were constructed. This vesicular amphiphile, the product of a dehydrocondensation reaction between amphiphilic aldehyde and a lipophilic aniline derivative, could be prepared within the giant vesicles. When a protected form of the aldehyde precursor was added to a suspension of giant vesicles containing the lipophilic aniline precursor and a catalyst, dehydrocondensation between the two precursors took place inside the vesicles and produced the same amphiphile as the one which constitutes the original vesicle. The newly formed amphiphiles self-assembled in the inner water pool to form small vesicles, which were eventually extruded through the outer layer of the original vesicle to the bulk water. Accordingly, this kinetic system can be designated as a self-reproducing system of giant vesicles.

Structure and Properties of 3-(Diethylboryl)pyridines(1).

3-(Diethylboryl)pyridine (1a), a versatile starting material for the preparation of arylpyridines, is notable for its stability under ambient conditions, in spite of little steric hindrance on the boron atom. (1)H and (13)C spectra of 1a indicated that the boryl group does not act as a mere pi-acceptor and that the boron atom is shielded by ca. 50 ppm even when compared with trivalent boron atoms conjugated with the pi-donor. A single-crystal X-ray crystallographic study for 1a revealed formation of a cyclic-tetramer with a void via the intermolecular boron-nitrogen coordination bond. Vapor pressure osmometry in various solvents suggested that 1a comprises the tetramer in these solutions. In order to know the actual structure, synthesis of 3-(2-methoxyethoxy)-5-(diethylboryl)pyridine (1b) and its scrambling experiment with 1a were carried out. Heating at 100 degrees C for 24 h was required to attain the equilibrium of the scrambling of the component molecules in the tetramers. This means that 3-(diethylboryl)pyridines 1a and 1b comprise the rigid cyclic-tetramer in solution at ambient temperature. Compound 1b is stable in aerated tetrahydrofuran containing up to 33 % water.