New details of blood clotting: a computer model of fibrinogen has been created
The joint work of scientists from the University of Illinois at Urbana-Champaign and the Mayo College of Medicine has shown what causes the elasticity of the fibrinogen molecule, which is actively involved in the formation of a blood clot.
Everyone knows that due to blood clotting, wounds are tightened, that there is such a disease – hemophilia, when the process of blood clots formation is disrupted, that due to a blood clot formed in the blood, a blockage of blood vessels (brain, heart, lungs) can occur and a person can die.
In other words, a blood clot both saves lives and takes away. In order to understand under what conditions and how thrombosis occurs, and which medications will help turn the process in one direction or another, scientists decided to establish in all details what determines the elasticity of fibrinogen fibers.
Let's explain. When the vessel wall is destroyed, platelets rush to the injury site and, under the influence of special proteins, thromboplastin is released, which together with other substances contributes to the transformation of the fibrinogen protein into its active form – fibrin. The resulting networks of elastic fibrin capture blood cells, which "plug" the remaining holes.
Fibrinogen molecules stretch very well (up to two to three times the original length). Due to this, they perform their function well – they stretch under blood pressure.
Scientists from the laboratory of Klaus Schulten (Klaus Schulten) from the University of Illinois decided to find out what determines the elasticity of fibrinogen. At the same time, the authors of the study decided not to be petty (or just the opposite?) and calculate the process with an accuracy of one atom.
And it all started with an appeal in 2006 to the Schulten group of Bernard Lim, a cardiologist from Mayo and an expert on blood clots. He conducted a series of experiments to measure the force required to stretch individual fibrinogen molecules. To do this, he used the methods of atomic force microscopy and discovered some regularity, which he called the "tensile force curve".
It turned out that the stretching of the molecule occurs in three successive stages. However, what exactly happens and which part of the molecule is responsible for each stage remained unclear to him. The fact is that fibrinogen is a symmetrical molecule, from the center of which intertwining spiral chains depart. The stretching of these spirals determines the elasticity of fibrinogen.
To establish this precisely, a team of scientists from Illinois conducted a kind of computer viscometry, modeled and calculated on a computer the stretching behavior of each atom of the fibrinogen molecule.
The result is this video (8.2 megabytes, MPG file), which proves that the "stretching force curve" really exists, that this is not a "trick of vision", but a true property of protein.
"Modeling has shown that each stage of stretching of the molecule occurs naturally, each section of the tangled spiral chains is straightened out strictly in a certain order," the authors write in a press release from the University of Illinois.
In addition, Lim found that the elasticity of fibrinogen is affected by the pH of the blood and the content of calcium ions in it. This means that by varying one or another parameter with the help of medications, doctors will be able to change the processes of thrombosis occurring in the human body.
"So we found out how we can influence the process of destruction or, conversely, "strengthening" of fibrinogen fibers," says Eric Lee, a graduate student at the University of Illinois.
The article devoted to the study was published in the journal Structure, and its shortened version can be found here (there are also several videos illustrating the processes occurring during the stretching of the molecule).
Portal "Eternal youth" www.vechnayamolodost.ru28.02.2008