I had a question about a specific clinical test last week and its relationship to the material we'd been discussing in class. In the previous lecture we'd learned about multi-subunit proteins with respect to Quarternary structures. In the lecture, multiple types of polymers - dimers, trimers, and tetramers - are said to be common. When I saw the term "dimer", it made me think of a clinical test that is run to rule out pulmonary embolism: a d-dimer. It is actually used in a number of different situations, including deep vein thrombosis (DVT) detection, and in the presence of stroke.
The test itself measures the level of Fibrin degradation. Fibrin is a non-globular protein that is involved in the clotting process - to actually actively work, Fibrinogen is converted to Fibrin by Thrombin, an enzyme involved in the clotting process.
A high Fibrin level usually indicates that further testing be done to determine whether or not a thrombus or embolus is present. Unfortunately, the d-dimer test itself is not always accurate. One of the problems with it is that conditions exist where false levels can be detected for a number of reasons including genetic makeup, presence of statins in the blood, and age to name a few. One condition where true high levels exist, however, is in a situation where the clotting cascade is behaving in such a way that its ability to produce Fibrin (from Fibrinogen, its precursor) is hyperactive.
In addition to function in clotting, Fibrin is also involved in platelet aggregation - its role here is in the signaling process of producing a hemostatic plug.
It was a "light-bulb" moment and I was surprised that I was able to make a connection to this from material being discussed in the classroom.
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