STRUCTURAL-PROPERTIES OF SEVERAL AMPHIPHILE CYCLODEXTRINS AND SOME RELATED NANOSPHERES - AN X-RAY-SCATTERING AND FREEZE-FRACTURE ELECTRON-MICROSCOPY STUDY

Amphiphilic cyclodextrins bearing fatty acyl chains covalently linked to their secondary hydroxyl groups are able to form nanospheres with a n internal organization. The structure of several cyclodextrins with d ifferent acyl chain lengths (CD-Cn) was investigated using X-ray scatt ering and freeze fracture electron microscopy. From the experimental d ata and using physicochemical arguments; we propose structure models. beta CD-C6, beta CD-C8, beta CD-C10, beta CD-C12, and gamma CD-C14 for m polar columns, surrounded by the paraffin chains, and associated in a 2-D hexagonal lattice. The structure of alpha CD-C14 and beta CD-C14 is body-centered cubic; it comprises one lattice of dimers aligned al ong the edges of the cubic cell and a second identical lattice with a translation of the half in the three directions. This results in the f ormation of two globules, one at the apex and one at the center of the cell. The structures are unusual for cyclodextrin molecules; they res ult from the presence of the numerous paraffin chains linked to each m olecule. Indeed, the structures are reminiscent of those found in lipi d systems.