The concept of micelles was first proposed in 1913 by McBain and has rationalized numerous experimental results of the self-aggregation of surfactants. It is generally agreed that the aggregation number (Nagg) for spherical micelles has no exact value and a certain distribution. However, our studies of calix[4]arene surfactants showed that they were monodisperse with a defined Nagg whose values are chosen from 6, 8, 12, 20, and 32. Interestingly, some of these numbers coincide with the face numbers of Platonic solids, thus we named them “Platonic micelles”. The preferred Nagg values were explained in relation to the mathematical Tammes problem: how to obtain the best coverage of a sphere surface with multiple identical circles. The coverage ratio D(N) can be calculated and produces maxima at N = 6, 12, 20, and 32, coinciding with the observed Nagg values. We presume that this “Platonic nature” may hold for any spherical micelles when Nagg is sufficiently small.

beta-1,3-D-glucans have been isolated from fungi as right-handed 6(1) triple helices. They are categorized by the side chains bound to the main triple helix through beta-(1-->6)-D-glycosyl linkage. Indeed, since a glucose-based side chain is water soluble, the presence and frequency of glucose-based side chains give rise to significant variation in the physical properties of the glucan family. Curdlan has no side chains and self-assembles to form an water-insoluble triple helical structure, while schizophyllan, which has a 1,6-D-glucose side chain on every third glucose unit along the main chain, is completely water soluble. A thermal fluctuation in the optical rotatory dispersion is observed for the side chain, indicating probable co-operative interaction between the side chains and water molecules. This paper documents molecular dynamics simulations in aqueous solution for three models of the beta-1,3-D-glucan series: curdlan (no side chain), schizophyllan (a beta-(1-->6)-D-glycosyl side-chain at every third position), and a hypothetical triple helix with a side chain at every sixth main-chain glucose unit. A decrease was observed in the helical pitch as the population of the side chain increased. Two types of hydrogen bonding via water molecules, the side chain/main chain and the side chain/side chain hydrogen bonding, play an important role in determination of the triple helix conformation. The formation of a one-dimensional cavity of diameter about 3.5 A was observed in the schizophyllan triple helix, while curdlan showed no such cavity. The side chain/side chain hydrogen bonding in schizophyllan and the hypothetical beta-1,3-D-glucan triple helix could cause the tilt of the main-chain glucose residues to the helix.

A certain length of poly(deoxyadenylic acid) (dA(X)) can form a novel complex with β-1,3-D-glucan schizophyllan (SPG) with a stoichiometric composition of one dA binding two main chain glucoses. We measured dilute solution properties for the complex with light and small-angle X-ray scattering as well as intrinsic viscosity and found that the complex behaves as a semiflexible rod without branching or cross-linking. We analyzed the data with the wormlike cylinder model, and the chain dimensions and the persistence length for the complexes were consistently determined. The chain flexibility was reduced to almost 25% upon complexation for dA/SPG and to 15% for S-dA/SPG, where S-dA denotes the phosphorothioated DNA analogue. The changes in the molar mass per unit length and the diameter indicated that the helix was elongated or stretched along the axis direction upon the complexation.

A novel calix[4]arene amphiphilic molecule, denoted by CCaL3, was synthesized and found to form a spherical micelle consisting of 12 molecules at low pH in aqueous solution. Furthermore, uniform Au nanoparticles with 2.0 nm in diameter were synthesized in aqueous solution on the template consisting of the four cysteines of the upper rim of CCaL3. Asymmetric field flow fractionation coupled with light scattering showed that there was no dispersity in the CCaL3 micellar aggregation number. When AuCl4(-) ions were added into the CCaL3 micelle solution, induced circular dichroism (ICD) appeared, indicating appearance of the structural chirality of the CCaL3/AuCl4(-) complex. A combination of electron microscopy and small-angle X-ray scattering showed that helically coiled bilayer sheets were formed upon addition of AuCl4(-). Subsequent reduction with the amine of cysteine moieties led to uniform Au nanoparticles formation with 2.0 nm in diameter on the micellar plate surface. The nanoparticle size was almost equal to the size of cavity constructed by the four cysteines on the calix[4]arene upper rim, indicating that the growth of Au nanoparticles was spatially controlled by the host-guest interaction between the cysteines and Au.