Drag force hydrodynamic limit

Simply based on the number of atoms participating in the primary structure of these biopolymers, proteins have a smaller hydrodynamic diameter (<30nm), whereas typical plasmid DNA molecules range from 100 to 400 nm. As a result, proteins are less susceptible to mechanical forces, especially hydrodynamic forces. This resistance is simply due to a size range that is well below the continuum limit of the fluid. In other words, when particle sizes are well below lOOnm (Figure 4.1-1) in aqueous solutions, they slip between water molecules rather than having a drag force applied continuously over the particle surface. 

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