the presence of a large excess of alpha 1 ( i ) chains over the normal ratio for type i collagen indicated that both type i collagen [ alpha 1 ( i ) ] 2 alpha 2 and [ alpha 1 ( i ) ] 3 or type i trimer were present both in the culture medium and in the extracellular matrix .
C0041455
type i collagen
C0015350
extracellular matrix