Small-Angle X-Ray Diffraction Patterns of Collagen

IN the investigation briefly reported here, the collagen fibres used were from beef achilles tendon. The diffraction patterns were obtained with an evacuated camera and a rotating anode X-ray tube having a copper or chromium target. The results discussed refer only to copper K α radiation; the chromium target was used solely for confirming intensity measurements. The observations on dry collagen were made with vacuum-dried fibres which remained in vacuo throughout the experiments, whereas wet fibres were mounted in a cell with beryllium windows and remained in a saturated atmosphere for the duration of the exposure. Photographs were obtained from which measurements were made of the intensities of twenty-five orders in the pattern for wet fibres, and twenty-three orders in the case of dry fibres. Exposure times involved may be indicated by giving the times required to give an intensity in the first order of D = 1.0 above the background. For dry achilles tendon this time was 2.5–3 hr., whereas for wet fibres the time was about thirty minutes, the apparatus running under identical conditions with the tube operated at 30 kV., 80 m.amp. The long spacing d of the dry fibres was 635 A. and for the wet fibres 670 A.