Protein Chemistry. Structure, Properties, Research Methods - Shendryk A.N. 2022

Methods for Experimental Investigation of Protein Structure
Methods for Determining Protein Molecular Weight
Determination of Molecular Weight by Sedimentation

Sedimentation is the settling of dissolved or suspended particles in a colloidal system (solution) under METABOLISM/18.html">The Influence of an externally applied potential field. The most common of these fields is the gravitational field. However, due to the relatively weak intensity of the Earth's gravitational field (acceleration due to gravity g = 9.8 m/s²), sedimentation proceeds very slowly within it. In the analytical ultracentrifuge, invented between 1922 and 1925 by Svedberg (Nobel Laureate in 1926), it is possible to generate gravitational fields tens and hundreds of thousands of times greater than g.

SVEDBERG, Theodor

August 30, 1884 – February 25, 1971

Nobel Prize in Chemistry, 1926

The Swedish chemist Theodor Svedberg was born at the Fleräng estate, near the town of Gävle. He was the only child of Elias Svedberg, an engineer and manager of a local iron foundry.

While studying at the Karolinska School in Örebro, Svedberg developed a passionate interest in physics, chemistry, and biology. Although he was primarily drawn to botany, he ultimately decided to become a chemist, believing that chemistry would allow him a deeper insight into biological processes. In January 1904, he entered Uppsala University, earning his bachelor's degree in September 1905. That same year, his first scientific paper was published. Svedberg continued his studies at Uppsala University and received his doctoral degree in 1907.

In 1912, Svedberg became Uppsala University's first lecturer in physical chemistry, holding this position for 38 years. He gained widespread recognition primarily for his groundbreaking research into the Physical Properties of colloidal systems.

To determine particle sizes in colloidal solutions, Svedberg employed an ultramicroscope designed by Richard Zsigmondy. He successfully demonstrated that colloidal solutions obey the classical Physical and Chemical laws established for dilute solutions. Nevertheless, in most cases, this method could not accurately resolve the sizes of the smallest particles or their size distribution.

Svedberg hypothesized that the sedimentation of colloidal particles could be accelerated under a stronger gravitational field generated by a centrifuge. During his stay at the University of Wisconsin in 1923, he set out to build an optical centrifuge in which particle sedimentation could be recorded photographically. Upon returning to Sweden in 1924, Svedberg, working alongside his colleague Herman Rinde, succeeded in achieving sedimentation free of convection. A year later, Svedberg discovered that biological macromolecules (Proteins) could also be made to sediment out of solution. Furthermore, the Sedimentation Rate of a protein allowed for Conclusions to be drawn about its molecular size. This finding provided the first indication that protein molecules possess a well-defined mass and shape. As a result of Svedberg's discoveries, the ultracentrifuge became an essential instrument in biochemical research. Today, sedimentation velocity is measured in units named in his honor.

In 1926, Svedberg was awarded the Nobel Prize in Chemistry “for his work on disperse systems.” In his presentation speech on behalf of the Royal Swedish Academy of Sciences, O. Wilhelm Öseen noted: “The motion of particles suspended in a liquid... clearly demonstrates the actual existence of molecules and, consequently, of atoms—a fact all the more significant given that, until very recently, an influential school of scientists dismissed these material particles as mere figments of the imagination.” In his Nobel lecture delivered the following year, Svedberg reviewed the technical and theoretical challenges associated with his work and outlined the immense potential value he believed the ultracentrifuge would hold for progress across many fields, including medicine, physics, chemistry, and industry.

In the new physical chemistry laboratory specially built for Svedberg by the Swedish government, he spent another 15 years refining the design of his centrifuge. In January 1926, the scientist tested a new oil-turbine ultracentrifuge model, achieving 40,100 revolutions per minute. Five years later, he developed a new model capable of reaching 56,000 revolutions per minute. A long series of improvements in rotor design eventually enabled the centrifuge to reach 120,000 revolutions per minute by 1936. At such speeds, the sedimenting particles were subjected to a force equal to 525,000 g (where g represents gravitational acceleration).

The next milestone in his protein research involved The Study of Hemoglobin and hemocyanin. He also analyzed the sedimentation characteristics of 100 proteins involved in the respiratory processes of numerous animals. It was demonstrated that the molecules of all these proteins are roughly spherical, monodisperse, and possess high molecular weights. Expanding The Scope of his ultracentrifugal studies to other biological macromolecules, Svedberg discovered that CARBOHYDRATES such as Cellulose and starch form long, thin, polydisperse molecules.

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Throughout his life, Svedberg maintained a keen interest in radioactivity. In the late 1920s, he investigated the effects of alpha particles emitted by radioactive substances on protein solutions. Following James Chadwick's Discovery of the neutron in 1932, Svedberg constructed a compact neutron generator to study the effects of neutron irradiation and to produce radioactive isotopes for use as chemical and biological tracers.

In 1949, having reached retirement age, Svedberg stepped down from his academic position. However, by special decree, he was permitted to retain the directorship of the newly established Gustaf Werner Institute for Nuclear Chemistry at Uppsala University, where a synchrocyclotron was installed largely due to his efforts.

Svedberg was a man of lively intellect and diverse interests. An accomplished amateur photographer, he was deeply passionate about botany and possessed one of the finest botanical collections in Sweden. He was married four times: to Andrea Andreen (1909), Jane Frodi (1916), Ingrid Blomquist (1938), and Margit Hallén (1948). He had six sons and six daughters.

Svedberg made a major contribution to strengthening the ties between academic science and the Structure/182.html">Practical Application of scientific achievements. For instance, during World War II, he spearheaded the establishment of synthetic rubber production in Sweden. A firm advocate of the international nature of science, he invited foreign scientists to work at Uppsala University. Working at the intersection of various scientific disciplines, Svedberg made a profound contribution to bridging physics, chemistry, and biology. The scientist passed away on February 25, 1971, in Örebro, Sweden.

Svedberg received numerous accolades, including the Berzelius Medal of the Royal Swedish Academy of Sciences (1944), the Franklin Medal of the Franklin Institute (1949), and the Adolf Gustaf Medal of Uppsala University (1964). He held honorary doctorates from the universities of Groningen, Wisconsin, Uppsala, Harvard, Oxford, Delaware, and Paris, and was a member of more than 30 professional societies, including the Royal Swedish Academy of Sciences, the Royal Society of London, the U.S. National Academy of Sciences, and the USSR Academy of Sciences.

Source of information:

Nobel Laureates: Encyclopedia: Transl. from English. — Moscow: Progress, 1992.

The gravitational field in an ultracentrifuge is generated by the rapid rotation of a rotor around its axis, which results in high centrifugal accelerations at the rotor periphery. Recall that, According to the “principle of equivalence” in Albert Einstein's general theory of relativity, gravitational fields and acceleration-induced fields are indistinguishable. They are fundamentally identical.

In a powerful gravitational field, diffusion forces are no longer able to govern the motion of sufficiently large molecules; that is, molecules can no longer remain evenly distributed throughout the volume, and instead undergo sedimentation in the direction of the centrifugal force.