13 August 1999
Vol 285, Issue 5430

About The Cover

Cover image expansion

COVER Twelve p-sulfonatocalix[4]arene anions (six are shown in colored space-fill mode), located at the vertices of an icosahedron, form a spherical supramolecular assembly (diameter, 2.8 nm). The sphere core (not shown) has a volume of 1700 Å3 and contains a cluster made up of two sodium ions and 30 water molecules. Lanthanide ions and pyridine N-oxide molecules (shown in stick mode) are important in determining the overall geometry. See page 1049 [Image: G. W. Orr, L. J. Barbour, J. L. Atwood]