Symmetry abounds in nature, but the beauty of proteins and other biological polymers lies in their asymmetry. Chirality, or handedness, of DNA and other biopolymers plays a critical role in their biochemical pathways: The binding properties of a left-handed DNA double helix differ significantly from those of the right-handed counterpart. Mimicking nature has not proven easy for scientists attempting to model, study, and engineer asymmetric polymers. Colloids—nanometer- to micron-sized particles—have emerged as molecular building-block candidates (see Physics Today, Physics Today June 2006, page 15 ). Left alone, however, they spontaneously clump together or form ordered crystals. A key to making helical structures is steric hindrance, in which the size of the building blocks—atoms, molecules, or colloids—constricts the resulting bond angles. A team of scientists from the Paris Institute of Technology in France and New York University have discovered that binary silica microspheres, joined into dumbbell shapes and with an...

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