Figure 3: Scanning transmission electron microscopy (STEM) analysis of NHMUK R4493.
From: Fibres and cellular structures preserved in 75-million–year-old dinosaur specimens
(a) Bright-field STEM micrograph depicting fibre fragments showing a banded pattern consistent with banding typically observed in collagen fibrils. The arrow indicates the fibre analysed in e and f. Scale bar, 200 nm. (b) Dark-field STEM micrograph showing detail of fibres in a. Scale bar, 100 nm. (c) STEM of fibre analysed by electron energy loss spectroscopy (EELS) indicating spectra locations. Scale bar, 50 nm. (d) EELS spectra showing a carbon peak on the fibre. A smaller peak is seen on the adjacent material. (e) Grey intensity distribution over fibre (indicated by the arrow) in a. Vertical lines in red are spaced 67 nm apart and generally correspond with peaks in grey intensity. (f) Periodicity characterization of e confirming the ∼67 nm banding. (g) Diagram representing the structure of a generic collagen molecule that produces 67 nm banding; I banded collagen fibrils surrounded by bone mineral matrix; II individual fibrils are composed of numerous collagen molecules arranged to produce 67 nm banding; III the canonical collagen triple helix.
