rotor: 12.5 cm x 18.8 cm x 15.7 cm; 4 15/16 in x 7 3/8 in x 6 3/16 in
shipping case: 39 cm x 21 cm x 22 cm; 15 3/8 in x 8 1/4 in x 8 11/16 in
overall in case: 8 3/4 in x 15 1/4 in x 8 1/4 in; 22.225 cm x 38.735 cm x 20.955 cm
United States: Wisconsin, Madison
This rotor was the workhorse behind an ultracentrifuge used in the Chemistry Department at the University of Wisconsin–Madison from the 1930s through the 1950s. Invented by Swedish chemist Theodor Svedberg in the mid-1920s, the ultracentrifuge was originally developed to analyze the weight of large molecules like proteins. Today it is commonly used to separate out molecules in solution.
Although based in Sweden for most of his life, Svedberg spent the spring of 1923 as a visiting professor at the University of Wisconsin, where he developed the optical centrifuge. On his return to Sweden, he modified the centrifuge to have a higher centrifugal field, creating the ultracentrifuge.
The ultracentrifuge works on the principle that heavy molecules sediment out of a solution at a speed relating to their weight. But, gravity alone is not strong enough to cause very light molecules to fall out of solution. To address this, the ultracentrifuge spins rapidly to create a force stronger than gravity, causing particularly light molecules to begin sedimenting out of solution. As the molecules fall, they are photographed. Analysis of these photographs can be used to establish the speed at which the molecules fell. Because that speed is related to how heavy a molecule is, it can be used to determine molecular weights.
Before the introduction of the ultracentrifuge, there was no reliable method for determining the molecular weight of proteins and other large molecules. For this and similar research, Svedberg won the Nobel Prize in Chemistry in 1926.
“The Analytical Ultracentrifuge: The First Half Century 1924–1974. Part I: Svedberg and the Early Experiments.” Pedersen, Kai O. <i>Fraction: News of Biochemical Instrumentation</i>. No. 1. Published by Spinco Division of Beckman Instruments, Inc. 1974.
“The Analytical Ultracentrifuge: The First Half Century 1924–1974. Part II: From the Colloid Experiments to DNA.” Williams, J.W. <i>Fraction: News of Biochemical Instrumentation</i>. No. 1. Published by Spinco Division of Beckman Instruments, Inc. 1974.
“Centrifuge, Ultra-.” p. 95. <i>Instruments of Science: An Historical Encyclopedia</i>. edited by Robert Bud and Deborah Jean Warner. Taylor & Francis. 1998.