Figure 5.

Cryogenic electron microscopy images of different stages of collagen mineralization and cryogenic electron tomography of collagen fibrils mineralized by DNA‐ACP. a–c) Unstained, reconstituted collagen fibrils that had been immersed in DNA‐ACP medium for 3, 5, and 24 h (bars: 200 nm). Minerals began to form within the fibrils after 3 h. At 24 h, complete intrafibrillar and extrafibrillar mineralization were achieved with apatite crystallites (indicated by SAED insert). d,e) 3D reconstruction from an electron tomography tilt series of DNA‐directed intrafibrillar mineralization (bars: 200 nm; movie available as Movie S2, Supporting Information). d[i]) Surface rendering of a collagen fibril that was mineralized for 24 h. d[ii]) Segmentation of the 3D volume to illustrate intrafibrillar and extrafibrillar mineralization (movie available as Movie S3, Supporting Information). e) 3D rendering of a heavily mineralized collagen fibril at 24 h.