protein threads in the blood extremely stretchy
Stopping bleeding is not only an important task for the organism - it is also an extreme mechanical strain. A large part of this load is carried by molecular threads, which, with a diameter of around 100 billionths of a meter, are around a thousand times thinner than a human hair. Scientists working with Martin Guthold from Wake Forest University in the US have now investigated what stresses such a fibrin molecule can withstand before it tears.
In their experiments, the researchers pulled on individual threads with the tip of a scanning force microscope and at the same time followed the process with a light microscope. It turned out that the fibrin threads can be stretched up to 2.8 times their normal length without being damaged. In order to tear them, they even have to be stretched 4 or 3 times, in some cases even more than six times their normal length.
These results on individual fibrin molecules are astonishing insofar as complete blood clots can only be stretched to twice their dimensions without rupturing. Apparently, the connections between the molecules are more likely to be lost than internal cracks. In any case, according to the scientists, fibrin is the most elastic natural thread-like material that we know. Even spider silk isn't as resistant to traction.