Collagen fibrils lateral packing

From the earlier work described here, it is clear that the collagen fibril is a complex structure. Many molecular species interplay to produce a fibril whose overall structure plays a specific role in the architecture of the tissue. In spite of such molecular heterogeneity, there are some central structural features of collagen packing that pertain more or less to all fibrillar structures. The purpose of this section is to discuss the generic and specific modulation in axial and lateral packing, and show how these lead to... 

TEM). The banding periodicity varies with age, species, pathology, and state (e.g., wet vs. dry) of the specimen. Molecularly different stmctures, like heterotypic type 1 and 111 collagen fibrils, show a similar liquid-like lateral ordering and axial packing. 

Connective tissue, such as tendon and cartilage, differs from other solid tissues In that most of Its volume Is made up of extracellular matrix rather than cells. This matrix Is packed with Insoluble protein fibers and contains proteoglycans, various multladhesive proteins, and hyaluronan, a very large, nonsulfated GAG. The most abundant fibrous protein In connective tissue Is collagen. Rubberlike elastin fibers, which can be stretched and relaxed, also are present In deformable sites (e.g., skin, tendons, heart). As discussed later, the fibronectins, a family of multladhesive matrix proteins, form their own distinct fibrils In the matrix of some connective tissues. Although several types of cells are found In connective tissues, the various ECM components are produced largely by cells called fibroblasts. 

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