DNA Origami: World’s Smallest Smiley Face.

Paul Rothemund of Caltech used "scaffolded DNA origami" technique to create the world’s smallest smiley face.

Rothemund made DNA strands into structures such as squares, smiley faces, stars, rectangles and hollow triangles, each about 100 nm across. He based each shape on a single strand of DNA roughly 7000 nucleotides long taken from a virus. (A nucleotide is the structural unit that makes up DNA and some other biological molecules.) The so-called "scaffold strand" was folded into the desired shape and held together by short "staple strands" of DNA.

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