Skin collagen has an unusual d-spacing.

Small angle X-ray diffraction patterns show a d-spacing of 65 +/- 0.5 nm for the collagen in wet intact skin of amphibian larvae (tadpole) as well as from that of nature frogs, chickens and mice. The collagen in these tissues is largely collagen I which exhibits a d-spacing of 67 +/- 0.5 nm in wet intact unstretched tendons. The d-spacing of the skin collagen did not decrease on drying, while it is well known that that of tendon collagen does decrease on drying. The reasons for the decreased d-spacing in the normal skin are not known but we suggest that the different glycosaminoglycan content of skin may be an important factor.