J. Appl. Cryst.の発刊に際して

Glycobiology: Toward Understanding the Function of Sugars.

About Dendrimers: Structure, Physical Properties, and Applications

THE recent synthesis of silica-based mesoporous materials1,2 by the cooperative assembly of periodic inorganic and surfactant-based structures has attracted great interest because it extends the range of molecular-sieve materials into the very-large-pore regime. If the synthetic approach can be generalized to transition-metal oxide mesostructures, the resulting nanocomposite materials might find applications in electrochromic or solid-electrolyte devices3,4, as high-surface-area redox catalysts5 and as substrates for biochemical separations. We have proposed recently6 that the matching of charge density at the surfactant/inorganic interfaces governs the assembly process; such co-organization of organic and inorganic phases is thought to be a key aspect of biomineralization7. Here we report a generalized approach to the synthesis of periodic mesophases of metal oxides and cationic or anionic surfactants under a range of pH conditions. We suggest that the assembly process is controlled by electrostatic complementarity between the inorganic ions in solution, the charged surfactant head groups and—when these charges both have the same sign—inorganic counterions. We identify a number of different general strategies for obtaining a variety of ordered composite materials.

Generalized synthesis of periodic surfactant/inorganic composite materials

Convergent Dendrons and Dendrimers: from Synthesis to Applications

The first observation of a cubic phase in lipid-water systems was reported in the early days of lipid polymorphism [1], at a time when the very existence of non-lamellar phases still met widespread skepticism. That cubic phase (Q230, see below) was the object of controversial reports: its structure was firmly established in 1967 [2,3]. Several other cubic phases were discovered since. In 1972, TARDIEU [4] listed five different phases of that class: more recently some of those phases, and others as well, have been observed in a variety of systems (see [5] and below).

The Cubic Phases of Liquid-Containing Systems: Physical Structure and Biological Implications

This study describes the preparation, characterization and in vitro release of monoolein aqueous dispersions (MAD) encapsulating quercetin (QT). As emulsifier, sodium cholate was employed at two different concentrations, namely 0.15% and 0.25% with respect to the total weight of the formulation. Cryogenic Transmission electron microscopy and X-ray analysis indicated that MAD015 are a mixture of vesicles and cubic structures, whilst MAD025 are mainly characterized by unilamellar vesicular structures. Photon correlation spectroscopy (PCS) and Sedimentation Field Flow Fractionation (SdFFF) showed a MAD size higher than 300 nm that over 100 days from analysis reduces up to 200 nm. In vitro Franz cell experiments showed that the two systems had a similar behaviour in the release of QT. Experiments on antioxidant activity of MAD containing QT demonstrated that their activity parallel with the content of encapsulated QT within the MAD formulations produced. Taken together these results allow us to conclude that MAD can be potentially proposed for the delivery of QT.

Monoolein aqueous dispersions as a delivery system for quercetin

The cyclic dinucleotide d(cGpGp) undergoes a self-association process in water to give, first, columnar aggregates similar to the four-stranded helix of poly(G). Successively, at higher concentration, these aggregates self-organize to give a cholesteric and a hexagonal mesophase, the former of which appears only in biphasic systems. The self-assembly process in isotropic solution has been studied by CD spectroscopy and the structure of the mesophases was investigated by optical microscopy and X-ray diffraction.

Chromonic lyomesophases formed by the self-assembly of the cyclic dinucleotide d(cGpGp)

X-ray diffraction results in magnetically oriented samples of aqueous solutions of the sodium salt of the dinucleoside phosphate G2 in the cholesteric N∗ phase are presented The symmetry of the diffraction confirms a model of stacking of tetrameric disks forming cylindrical aggregates in the N∗ phase A weak band at 7 A not previously observed gives further information on the inner structure of the cylindrical aggregates Analysis of the diffraction peak position in low angle evidences a change in functional behaviour of the distance α between cylinder axes as a function of the volume concentration cv of G2 In the H phase, a α cv −1/2 as it should for infinite cylinders; in the N∗ phase, a α cv −1/3, typical of finite cylinders The cross-over of functional behaviour occurs at the N∗[sbnd]H phase transition There is therefore cylinder growth along the N∗ phase

Structural study of the aggregates formed by the dinucleoside phosphate G2 in aqueous solution

While the handedness of the cholesteric phases formed by assembled guanosine derivatives (G-wires) follow the correlation right-handed helices-->right-handed cholesterics (left-handed -->left-handed), the cholesteric phase formed by B-DNA (right-handed helix) is left-handed. This apparent discrepancy is overcome by considering pitch (p) variations with temperature. Plots of p(-1) versus T(-1) have, in fact, the same trend (positive intercept and negative slope) in the case of right-handed G-wires and B-DNA, while for the left-handed G-wire of deoxyguanosine monophosphate (dGMP), the opposite behavior is observed (negative intercept and positive slope). Therefore, the relation between molecular handedness and cholesteric helicity cannot, in general, be assessed by using measurements based on a single temperature; hence the temperature variation of the cholesteric parameters should be investigated. In all cases there is no remarkable salt effect on the cholesteric parameters.

Paolo Mariani

Papers

The Cubic Phases of Liquid-Containing Systems: Physical Structure and Biological Implications

Monoolein aqueous dispersions as a delivery system for quercetin

Chromonic lyomesophases formed by the self-assembly of the cyclic dinucleotide d(cGpGp)

Structural study of the aggregates formed by the dinucleoside phosphate G2 in aqueous solution

The Chirality of the Cholesteric Phases of DNA and G-Wires: Its Connection to their Molecular Structures