= U. R. Nilsson
{c}
<U. R. Nilsson> coauthored a 1965 study isolating beta1F-globulin from human <blood serum> and identifying it as the fifth component of the <complement system>, now called <complement C5>. The assignment linked an isolated <protein> to its function in a multicomponent reaction.<Isolation of beta 1F-globulin from human serum and its characterization as the fifth component of complement by U. R. Nilsson and others>[Journal of Experimental Medicine 122, 277–298, original byline and Abstract]{ref}
The study used kinetic relationships to place the component after <Complement C3>, and its reported hemolytic function depended on <complement C6>. These observations supplied information about reaction order and partner dependence, beyond merely recovering a protein fraction.<Isolation of beta 1F-globulin from human serum and its characterization as the fifth component of complement by U. R. Nilsson and others>[Abstract, kinetic ordering and C6-dependent hemolytic activity]{ref}
The logic resembles locating a missing part in a coupled system. If adding a separated component restores a particular function only when another required component is present, the observation identifies a dependency. It does not mean that the added protein alone performs every downstream event. Comparing complete and incomplete combinations can therefore reveal organization hidden by a single measurement of total <protein>.
The work also distinguishes abundance from activity. Detecting the isolated material and demonstrating its contribution to <hemolysis> answer different experimental questions. The credited contribution helped connect a named serum protein with a defined position and role in complement function, providing a reference for later studies of its activation and products.
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