Kent State University Biomaterials Worksheet

Collagen and proteoglycans are most important macromolecules of the corneal extra cellularmatrix.
26 different type of collagen which can be categorized into 3 have been described in vertebrates
thus far.
1. Fibril-forming collagens
2. FACIT collagens
3. Nonfibrillar collagens
All type of collagens have a triple helix structure composed of three polypeptide, known as
alpha-chains, consisting of Gly-X-Y repeats where X is any amino acids and Y is frequently
proline or hyroxyproline. Each chain is a left handed helix, and the three chains wind around
each other in a right handed super helix.
proteoglycans are macromolecules composed of a protein core with covalently linked
glycosaminoglycan side chains with predominant components dermatan sulfate, keratan sulfate
and with smaller amount of heparin sulfate.
Collagen and proteoglycans always coexist in the extra-cellular matrix of the connective tissue.
Each of these components has its own specific role in the tissue. Collagen is a structure that gives
stiffness and a high degree of tensile strength to the matrix; the highly hydrated proteoglycans
confer rigidity to the matrix as well as allowing transport of ‘moving’ molecules and impeding
diffusion of large molecules due to their mesh-like structure. In actual fact, collagen and
proteoglycans also interact with each other, for instance, by influencing collagen fibril formation
and growth as well as the assembly of the collagen fibrils and their three-dimensional
arrangement according to the specific primary function of the tissue.