Ultracentrifuge


Also found in: Dictionary, Thesaurus, Medical, Wikipedia.

ultracentrifuge

[‚əl·trə′sen·trə‚fyüj]
(engineering)
A laboratory instrument which develops centrifugal fields of more than 100,000 times gravity, used for the quantitative measurement of sedimentation velocity or sedimentation equilibrium, or for the separation of solutes in liquid solutions to study high polymers, particularly proteins, nucleic acids, viruses, and other macromolecules of biological origin.

Ultracentrifuge

 

a device for separating particles less than 100 nanometers in size, such as colloids, subcellular particles, and macromolecules of proteins, nucleic acids, lipids, polysaccharides, and synthetic polymers, which are suspended or dissolved in a liquid. This is achieved by the rapid rotation of a rotor, which creates a centrifugal field with an acceleration many orders greater than the acceleration of gravity.

Ultracentrifuges are classified as preparative, analytical, or preparative-analytical according to their purpose and design.

Preparative ultracentrifuges are equipped with fixed-angle rotors, which have recesses for test tubes, beakers, or bottles, tilted at an angle of 20°-40° to the vertical axis of the rotor. Some have swinging-bucket rotors, with beakers that tilt 90° upon rotation. There are also ultracentrifuges with zonal or continuous-action rotors, with a single large vessel for the liquid being fractionated. Preparative ultracentrifuges are used to isolate individual components from complex mixtures.

Analytical ultracentrifuges have rotors with through-cylindrical recesses, in which special transparent vessels are inserted for the solutions or suspensions to be analyzed. The redistribution of particles in the solutions and suspensions may be observed directly during rotor rotation with the aid of special optical systems, such as refractometric or absorption devices. Some analytical ultracentrifuges are connected to electronic computers, which carry out the automatic processing of experimental data.

The first ultracentrifuge, designed for studying the motion of particles invisible under a microscope, was constructed by the Swedish scientist T. Svedberg in 1923 (discovery announced in 1924). This ultracentrifuge, in which a centrifugal force of up to 5,000 g was achieved, had an absorption optical system and was used to study the motion of gold particles with a diameter of approximately 5 nanometers. In 1926, Svedberg built the first highspeed ultracentrifuge (41,000 rpm, acceleration up to 105 g), which made possible the analytical study of proteins in solutions, particularly the study of hemoglobin. In 1939 he designed an analytical ultracentrifuge with a steel rotor (65,000 rpm).

The vast majority of modern laboratory ultracentrifuges are electrically driven and have aluminum or titanium rotors. In the USSR and abroad many types of ultracentrifuges are being produced in which accelerations of up to 500,000 g are created, and the separation of particles and molecules is carried out in volumes measuring tens and hundreds of milliliters.

REFERENCES

Lotts, Iu. A., and A. Ia. Ozherel’ev. “Analiticheskaia ul’tratsentrifuga.” Unikal’nyepribory, 1970, no. 5.
Svedberg, T, and K. O. Pedersen. The Ultracentrifuge. Oxford, 1940.

A. D. MOROZKIN

References in periodicals archive ?
He explained that ultracentrifuges can be applied in food and drug industries but their main use is in research as well as oil, gas and petrochemical industries to separate particles with different density.
An important aspect of ultracentrifuge operations is rotor replacement.
The chemical scroll pump has shown a much higher resistance to the slugs of solution used in ultracentrifuges, with practically no maintenance required upon transport of ultracentrifuge media solutions of water and glycerin.
There is one commercial laboratory (Atherotech Inc., Birmingham, AL) that uses the micro-sample preparative ultracentrifuge method to give you direct measurements of all lipoprotein components, including lipemic specimens.
He added that the ultracentrifuge machines with the 60,000rpm power had merely been developed in the US and Japan before Iran.
In each measurement, 2 parts of an aqueous NaCl solution (11.5 g NaCl plus 0.1 g EDTA per 1 L water; d = 1.006) are added to 1 part patient serum, and the procedure is followed by ultracentrifugation in a Beckman 50.4 Ti fixed-angle rotor with a Beckman Coulter L8-80MR or L80-XP ultracentrifuge (Beckman Coulter) at 45 000 rpm for 11 h at 10[degrees]C, resulting in 218 068g.
Nonimmunologic procedures include: a) ultracentrifuge concentration--the material from cleared suspensions is sedimented by ultracentrifugation, resuspended in a smaller volume and then prepared by the standard two-step drop method (32); b) agar diffusion--a 20-50 [20- to 50-[micro]L drop of suspension is placed on 1% agar.
As the market for bench-top systems grows, however, the demand for floor-standing, high-speed and ultracentrifuge systems is expected to decline.
A protective role for HDL-C was less readily accepted, although HDL-C subclasses and their inverse association with CAD had been clearly demonstrated in the early 1950s by John Gofman's seminal studies (1) using the technically challenging analytical ultracentrifuge at the Donner Laboratory of the University of California at Berkeley.
The Optima MAX Personal Ultracentrifuge System has the first rotor to reach 1 million x g...The US Patent and Trademark Office has allowed Visible Genetics' patent, "Virtual DNA Sequencer." The patent depicts a DNA sequencing system created by networking many independent, high-speed, automated DNA sequencers to a single computer, capable of high sequencing throughput...National Instruments introduced a new version of its PID Toolkit that adds automating and gain scheduling capabilities.
The MLA-50 High-Capacity Rotor for the Optima MAX-XP Tabletop Ultracentrifuge from Beckman Coulter offers a 194 mL capacity that allows more sample to be processed per run.