FAU researchers explain unique property of collagen
The protein collagen is the main component of human skin. It has unique properties: it remains soft and flexible under low stress and stiffens when stress is increased. FAU researchers have now discovered the mechanisms that cause collagen’s mechanical stiffness to adapt to external stress. Their observations could contribute to improving synthetic materials. The researchers’ findings have been published in the journal ‘Proceedings of the National Academy of Sciences’ (PNAS)* .
Collagen is widely known as the protein responsible for keeping the skin firm. It is the most abundant protein in the human body and is responsible for the mechanical stability of the skin, the tendons, the muscles, the bones and connective tissue. Collagen is unique in the sense that it remains soft and flexible under low stress and becomes stiffer when stress is increased. Collagen therefore ensures that the body’s cells are able to withstand a certain degree of internal and external stress. This extraordinary property is the reason why collagen can also be used for commercial purposes, for instance, as tanned collagen for shoe leather or in artificial heart valves. Together with researchers from VU University Amsterdam and Harvard University FAU physicists have now uncovered another aspect of this mechanical behaviour of collagen.
The structure of collagen is similar to that of a rope. Three chains of collagen molecules wind around each other and form a rope. Several of these ropes, in turn, assemble into what are known as fibrils, stronger ropes. These then combine to form collagen fibres. The researchers have now shown that collagen forms networks from these fibres. The individual network fibres can be flexed easily but it is hard to stretch them. Under increased stress, more and more fibres are stretched and begin to organise into networks similar to tight fishnets. Using mathematical analysis, the researchers established that not all fibres bear the same load. The proportion of load-bearing fibres changes and ensures that the entire network’s mechanical stability adapts perfectly to external mechanical stress, irrespective of how tightly the fibres are assembled. The researchers hope that this principle can be used in future to design new synthetic materials with adaptive mechanical properties.
*Albert James Licup, Stefan Münster, Ahbinav Sharma et al.: Stress controls the mechanics of collagen networks. Proceedings of the National Academy of Sciences (USA). doi: 10.1073/pnas.1504258112
Prof. Dr. Ben Fabry
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