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Sizing Biological Samples by Photosedimentation Techniques
Author(s) -
Middelberg Anton P. J.,
Bogle I. David L.,
Snoswell Mark A.
Publication year - 1990
Publication title -
biotechnology progress
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.572
H-Index - 129
eISSN - 1520-6033
pISSN - 8756-7938
DOI - 10.1021/bp00004a004
Subject(s) - sizing , centrifuge , diffusion , sedimentation , analytical chemistry (journal) , escherichia coli , chromatography , spin (aerodynamics) , chemistry , materials science , mechanics , physics , thermodynamics , biology , paleontology , biochemistry , organic chemistry , sediment , gene , nuclear physics
The performance of the Joyce‐Loebl disk centrifuge in the sizing of Escherichia coli cells, protein inclusion bodies, and cell debris is evaluated. The need for a density gradient that extends throughout the entire spin fluid is highlighted, and a set of standard conditions that fulfill this requirement is defined. E. coli cells experience a reduction in their Stokes diameter when exposed to ethanol, indicating that a spin‐buffer fluid combination such as glycerol‐water is to be preferred for the sizing of bacteria. The instrument baseline is influenced by the presence of particles, and a method of estimating the baseline is described. The sizing of small particles is further complicated by baseline drift due to temperature sensitivity of the optical yoke. An analysis of diffusion in the spin fluid is conducted, and an expression for the sedimentation:diffusive flux ratio is derived. For the current samples, it is shown that diffusion within the spin fluid does not lead to significant errors for 0.15‐μm particles, whereas the phenomenon may be significant at the manufacturer's size limit of 0.01 μm.