Syndecans are transmembrane proteoglycans that, together with integrins, control 
cell interactions with extracellular matrix components. Despite structural 
similarities between all members of the syndecan family, their specific 
attachment to extracellular matrix proteins is defined by heparan and 
chondroitin chains. We postulate various unbinding kinetics for each type of 
single syndecan complex. Force spectroscopy data, recorded by atomic force 
microscope, were analyzed using two theoretical approaches describing 
force-induced unbinding, authored by Bell-Evans and Dudko-Hummer-Szabo. Our 
results reveal distinct unbinding pathways dependent on the syndecan family 
member. Syndecan-1 unbinds by passing over two energy barriers, inner and outer. 
Syndecan-4 unbinds by crossing over only one energy barrier. It has already been 
reported that both syndecans bear heparan chains that are structurally 
indistinguishable. Our finding reveals that unbinding of single syndecan 
complexes is family-member-dependent. Distinct unbinding pathways can be 
attributed to structural differences of heparan and chondroitin chains.