Chapman J A
Biopolymers. 1989 Aug;28(8):1367-82. doi: 10.1002/bip.360280803.
A possible mechanism for regulating the lateral growth of collagen fibrils in vivo is considered. A growth inhibitor associated with a particular part of the long semiflexible collagen molecule restricts that part of the molecule to the surface of the growing assembly. Lateral accretion ceases when these inhibitors form a complete circumferential layer around the fibril surface. Cell-mediated removal of the inhibitors allows lateral growth to proceed to a second limiting layer, and so on to subsequent limiting layers. In this way, cycles of inhibitor removal and limited lateral accretion permit growth to be synchronized over large populations of fibrils. Observed diameter distributions in bundles of embryonic and neonatal fibrils are those expected from a mechanism of this kind. The mechanism depends on the existence of axial order (D-periodicity) in fibrils, but not on any specific lateral packing of molecules. Rather, contacts between newly assembled molecules are presumed to be partly fluid-like in lateral directions (except where covalent cross-links have formed). Some initial fluidity in lateral packing prior to cross-linking does not preclude the subsequent emergence of quasi-crystalline packing as cross-links form. The cylindrical shape of fibrils in vivo may also be attributable in part to fluidity of intermolecular contacts at the growing surface.
本文探讨了一种在体内调节胶原纤维侧向生长的可能机制。一种与长半柔性胶原分子特定部分相关的生长抑制剂，会将该分子部分限制在生长聚集体的表面。当这些抑制剂在纤维表面形成完整的圆周层时，侧向堆积就会停止。细胞介导的抑制剂去除使得侧向生长能够进行到第二个限制层，依此类推至后续的限制层。通过这种方式，抑制剂去除和有限侧向堆积的循环使得大量纤维的生长能够同步。在胚胎和新生纤维束中观察到的直径分布正是这种机制所预期的。该机制依赖于纤维中轴向秩序（D周期性）的存在，但不依赖于分子的任何特定侧向堆积。相反，新组装分子之间的接触在侧向方向上被认为部分类似流体（共价交联形成的地方除外）。交联之前侧向堆积的一些初始流动性并不排除随着交联形成随后出现准晶体堆积。体内纤维的圆柱形形状也可能部分归因于生长表面分子间接触的流动性。
