Collagen is an extracellular matrix found in the dermis, ligaments, bones, etc., and accounts for approximately 30% of the total protein in the human body. The most abundant type of collagen is type I collagen, which has a molecular weight of approximately 300 kDa and comprises three polypeptides.
The molecular structure of collagen is a right-handed triple helix region and telopeptide (non-helical) regions at the N-terminal and C-terminal of the molecule. These telopeptide regions are composed of two α1 chains and one α2 chain. The triple helix region is conserved among species and shows low immunogenicity, while the telopeptide regions exhibit high immunogenicity. Removal of the telopeptide regions by protease treatment produces atelocollagen, which retains the same properties as collagen. We have developed atelocollagen-based medical devices.

Unwinding of the triple helix of collagen and atelocollagen by heat degeneration produces gelatine. Gelatine is a random coil single polypeptide and has high immunogenicity.
Peptides obtained by hydrolysis with strong acids, strong alkalis, or by enzymatic treatment are called hydrolysed collagen. Gelatine and hydrolysed collagen have totally different properties from collagen due to their structural differences compared to collagen.