ULTRACENTRIFUGES 



363 



ULTRACENTRIFUGES 



high viscosity, as well as certain of their 

 molecular components after disruption 

 of the cell. In fact it was the latter 

 that led Svedberg and his associates 

 to experiment with machines to de- 

 velop higher centrifugal force, optical 

 methods of recording the behavior of 

 mixtures during rotation, and suitable 

 mathematical formula for interpreting 

 the molecular weights of proteins (Sved- 

 berg, T. and K. C. Pedersen, The 

 Ultracentrifuge. Oxford Univ. Press 

 1940). Svedberg's many years of ex- 

 perimentation culminated in an oil- 

 turbine driven rotor surrounded by an 

 atmosphere of hydrogen to reduce 

 heating and hence, convection which 

 is always a troublesome problem in the 

 high speed centrifuging of mixtures. 

 The safe operating speed of the Sved- 

 berg ultracentrifuge is said to be about 

 67,000 R.P.M., producing about 350,000 

 times gravity. By means of this instru- 

 ment Svedberg and his associates have 

 demonstrated that the protein molecule 

 is relatively large. In addition, they 

 have made an important contribution 

 to biology by determining the molecular 

 weights of many of them. 



Because the oil-driven ultracentri- 

 fuge is relatively complicated and 

 costly, only 9 or 10 of them have been 

 made (Gay, G. W., Scientific American 

 1951, 184, 43). In 1930, J. W. Beams 

 developed the air-turbine ultracentri- 

 fuge of Henriot and Huguenard to use 

 in connection with some experiments 

 in physics (J. Appl. Phys., 1937, 8, 

 795). This instrument consists of a 

 cone shaped rotor which is supported 

 and driven bj'^ air under pressure from 

 properly directed jets. It is relatively 

 simple (costs less than $100.00) and has 

 proven most useful for histological 

 and cytological studies. Displacement 

 of materials such as Golgi apparatus, 

 mitochondria, Nissl bodies, neuro- 

 fibrillae, centrosomes, chromosomes, 

 spindles, acrosomes, plastids, nuclei 

 and nuclear components, intracellular 

 virus bodies, membrane materials, 

 erythrocyte components, secretion 

 products, vitamine C granules, organizer 

 substances, enzymes, bacteriophage, 

 and sarcoma virus have been observed. 

 In addition, it has been successfully 

 used to study polarity in both plants 

 and animals as well as the relative 

 viscosity of certain cancer cells. Thus, 

 by use of this method, information has 

 been gained concerning both the struc- 

 ture and function of many cellular com- 

 ponents and inclusions both inside and 

 outside the cell. 



E. N. Harvey has adapted his centri- 

 fuge-microscope principle to the air- 



turbine rotor thus making possible the 

 direct observation of cells in a centrif- 

 ugal field of 100,000 to 250,000 times 

 gravity (Biol. Bull. 1934, 66, 48). 



While the air-turbine ultracentrifuge 

 above described has proved satisfac- 

 tory for the study of many materials 

 within cells, it is not so suitable for 

 the separation of colloidal solutions 

 within a test tube. This is because of 

 the convection induced by the slight 

 heating of the rotor as it spins in air at 

 atmospheric pressure. This difficulty 

 has been overcome by the development 

 of the air-turbine vacuum-tj^pe ultra- 

 centrifuge. This machine consists of 

 a large rotor (4 to 7 inch) situated in- 

 side a vacuum tight chamber which 

 is driven and supported by an air- 

 turbine of the type described above, 

 located outside and vertically above the 

 vacuum tight chamber. The turbine 

 and rotor are connected by a flexible 

 shaft which enters the vacuum chamber 

 through a vacuum tight oil gland. By 

 this means a convection free centrifugal 

 field is established, the intensity of 

 which is limited only by the bursting 

 strength of the rotor spining the vac- 

 uum chamber. (Beams, J. W., J. 

 Appl. Phys., 1937, 8, 795; Rev. Mod. 

 Phys., 1938, 10, 245; Bisco, Pickels and 

 Wyckoff, J. Exp. Med., 1936, 64, 39). 



The development of this compara- 

 tively inexpensive centrifuge has made 

 available to many biophysical and bio- 

 chemical laboratories an instrument 

 comparable to, if not superior to, the 

 oil-turbine ultracentrifuge of Sved- 

 berg. With it investigators have con- 

 centrated, separated, and determined 

 the molecular weights of substances 

 such as many different types of virus, 

 antibodies, bacteriophage, cancer 

 agents, hormones, and various proto- 

 plasmic constituents. 



New uses for the ultracentrifuge in 

 biological research are continually ap- 

 pearing. For example, press reports 

 state that Gofman and associates have 

 separated cholesterol from human blood 

 by use of this machine. Their studies 

 indicate that it may be possible to antici- 

 pate certain circulatory diseases, such as 

 high blood pressure and arteriosclerosis, 

 by this technique. In other words, 

 eventually we may have available 

 "diagnostic ultracentrifuges". 



The air-turbine tubular-type ultra- 

 centrifuge has been used successfully 

 to separate uranium 235 from uranium 

 238 (Smyth, H. D., Atomic Energy for 

 Military Purpo.ses, Princeton Univ. 

 Press, 1945). This machine was first 

 described by J. W. Beams, and has 

 become a subject of classified military 



