Purslow P P, Wess T J, Hukins D W
School of Molecular and Medical Biosciences, University of Wales College of Cardiff, UK.
J Exp Biol. 1998 Jan;201(Pt 1):135-42. doi: 10.1242/jeb.201.1.135.
Collagen fibres form cross-helical, cross-ply or quasi-random feltworks in extensible connective tissues; strain-induced reorientation of these networks gives rise to the non-linear mechanical properties of connective tissue at finite strains. Such tissues are also generally viscoelastic (i.e. display time-dependent properties). The hypothesis that time-dependent reorientation of collagen fibres is responsible for the viscoelasticity of such tissues is examined here using time-resolved X-ray diffraction measurements during stress-relaxation and creep transients applied to rat skin and bovine intramuscular connective tissue. Differences in the intensity and angular orientation of the third and fifth orders of the 67 nm meridional D-spacing of collagen molecules were shown before and after the application of loads or displacements. However, no changes in the D-spacing or angular orientation of collagen occurred during the time course of either stress-relaxation or creep in both tissues. This indicates that collagen fibre reorientation is not a primary source of their viscoelastic properties. The non-linear (strain-dependent) nature of the stress-relaxation response in these tissues suggests that relaxation processes within the collagen fibres or at the fibre-matrix interface may be responsible for their viscoelastic nature.
在可延展的结缔组织中，胶原纤维形成交叉螺旋、交叉层状或准随机的纤维网络；这些网络的应变诱导重排导致结缔组织在有限应变下呈现非线性力学特性。这类组织通常也具有粘弹性（即表现出与时间相关的特性）。本文利用时间分辨X射线衍射测量技术，在对大鼠皮肤和牛肌肉内结缔组织施加应力松弛和蠕变瞬变过程中，检验了胶原纤维随时间的重排是此类组织粘弹性成因的假说。在施加负荷或位移前后，胶原分子67纳米子午向D间距的三阶和五阶强度及角取向出现了差异。然而，在两种组织的应力松弛或蠕变过程中，胶原的D间距或角取向均未发生变化。这表明胶原纤维重排并非其粘弹性特性的主要来源。这些组织中应力松弛响应的非线性（应变依赖性）特性表明，胶原纤维内部或纤维 - 基质界面处的松弛过程可能是其粘弹性的成因。
