Fig. 2.

The depth-wise variation in SAXS derived parameters in bovine articular cartilage. Sample SAXS patterns from a single sample of full thickness cartilage are shown in part (a) (beam-stop region masked with a circle). The depth-wise fibrillar alignment (ν-parameter), collagen D-Period and intrafibrillar order versus depth are shown in (b)–(d) respectively. In (b), blue line-patterns show different degrees of fibrillar alignment across the tissue and the correlation with ν-parameter. A representative radial integration is shown in (e) which indicates how the ν-parameter is calculated which a representative azimuthal integration is shown in (f) and (g) showing how both D-period and intrafibrillar order are determined, respectively [40]. (h) Schematic showing the structural meaning of fibrillar strain and order, in terms of inter-molecular arrangement within the fibril and related SAXS pattern. The staggered arrangement of tropocollagen molecules is shown schematically in the centre, with the regions of high density (overlap) and low density (gap) shown at the fibrillar (centre) and intrafibrillar level (offset centre). The left images show fibrils undergoing compressive strain (shift in D-period) without intrafibrillar rearrangement (shift in meridional SAXS peak). The right image show intrafibrillar rearrangements of molecules (disordering), leading to reduction of SAXS peak intensity. As the data shown is from a single sample, no error bars are indicated on the plots. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)