Page 22 - Subyek Encyclopedia - Encyclopedia of Separation Science

Sepsci*11*TSK*Venkatachala=BG
I / CENTRIFUGATION 17

Conclusion icals. A mandatory part of any new protein pharma-
ceutical process is the acceptance by regulatory
Protein separations can be achieved by a variety of
authorities of the separation process involved. That
afRnity techniques, but separations in the
synthesized afRnity ligand separation processes
chromatography mode are by far the most widely have now been fully accepted by the foremost regula-
used. Nature deRned an appropriate pathway to highly tory authority, the USA’s Food and Drug Administra-
efRcient separation } utilization of the phenom- tion, conRrms a worldwide acceptance of the power
enon of the automatic recognition mechanism existing of ligand design technologies.
between a given protein and at least one other. By
covalently bonding one of the pair onto an inert matrix See Colour Plate 1.
a theoretically simple separation process can be de-
vised. Although these immunoafRnity separations Further Reading
are widely practised today, severe limitations exist, not
least of which are cost and instability of the afRn- Briefs K-G and Kula M-R (1900) Fast protein chromatogra-
ity medium when in use. As modern design aids have phy on analytical and preparative scale using modiRed
become commonplace, in conjunction with newer micro-porous membranes. Chemical Engineering
Science 47: 141}149.
techniques such as the development of combinatorial Burton SJ, Stead CV and Lowe CR (1988) Design and
library arrays, it has proved possible to mimic nature applications of biomimetic anthraquinone dyes. Journal
and replace immunoafRnity matrices by speciR- of Chromatography 455: 201}216.
cally designed synthetic ligands. These new ligands not Chase HA (1994) PuriRcation of proteins using expanded
only accurately emulate the exquisite precision of the beds. Trends in Biotechnology 12: 296}305.
natural protein}protein interaction mechanisms, but Dean PDG, Johnson WS and Middle FA (1985) AfTnity
also provide the opportunity to manipulate the ligand Chromatography: A Practical Approach. Oxford: IRL
structures, thus offering far more efRcient Press.
Jones K (1990) A review of afRnity chromatography.
separations than any previously achieved. For a given
Chromatographia 32: 469}480.
protein, from whatever source and at any dilution, it is
now possible virtually to guarantee that a highly cost- Kenny A and Fowell S (1990) Methods in Molecular Biol-
ogy: Practical Protein Chemistry. New York: Humana
effective and highly efRcient separation pro- Press.
cess can be developed for eventual commercial use. Kopperschlager G (1994) AfRnity extraction with dye-
Designed ligand processes have already been ad- ligands. Methods in Enzymology 228: 121}129.
opted for several very large biotechnology projects Walker JM and Gaastra W (1987) Techniques in Molecular
scheduled to manufacture bulk protein pharmaceut- Biology. London: Croom Helm.

CENTRIFUGATION

D. N. Taulbee and M. Mercedes Maroto-Valer, has been employed for well over 100 years. Applica-
University of Kentucky-Center for Applied Energy tions that range from the mundane, industrial-scale
Research, Lexington, KY, USA dewatering of coal Rnes to the provision of an invalu-
able tool for biomedical research.
Copyright ^ 2000 Academic Press
The Rrst scientiRc studies conducted by Knight in
Introduction 1806 reported the differences in orientation of
roots and stems of seedlings when placed in a rotating
Centrifugation is a mechanical process that utilizes an wheel. However, it was not until some 60 years later
applied centrifugal force Reld to separate the compo- that centrifuges were Rrst used in industrial applica-
nents of a mixture according to density and/or tions. The Rrst continuous centrifuge, designed in
particle size. The principles that govern particle be- 1878 by the Swedish inventor De Laval to separate
haviour during centrifugation are intuitively compre- cream from milk, opened the door to a broad range of
hensible. This may, in part, explain why centrifu- industrial applications. About this same time, the Rrst
gation is seldom a part of post-secondary science centrifuges containing small test tubes appeared.
curricula despite the broad range of scientiRc, medical These were modest, hand-operated units that attained
and industrial applications in which this technique speeds up to 3000 rpm. The Rrst electrically driven