Size and Density of Protein Inclusion Bodies

The size distribution and density of two types of protein inclusion bodies arising from the synthesis in E. coli of recombinant calf prochymosin and γ–interferon were examined. A combination of electrical sensing zone and centrifugal sedimentation techniques were used to characterize the particles. The mean size and standard deviation (sd) of the distributions for the γ–interferon and prochymosin–based inclusion bodies were 0.81 μm, sd 0.17 μm, and 1.28 μm, sd 0.46 μm, respectively. Sedimentation studies indicated that the density of the protein inclusion bodies increases with the density of the suspending solvent. These density variations are consistent with the bodies having a voidage, accessible to the suspending fluid of 70% (γ–interferon) and 85% (prochymosin) of the total volume.