Protein Sample Ultrafiltration

• What is ultrafiltration?
• Ultrafiltration vs Dialysis
• Ultrafiltration vs Microfiltration Membranes
• How to use ultrafiltration in your lab?

What is ultrafiltration?

Ultrafiltration (UF) is the process of separating extremely small particles and dissolved molecules from fluids. The primary basis for separation is molecular size, although filter permeability can be affected by the chemical, molecular or electrostatic properties of the sample. To be separated by ultrafiltration, molecules must differ in size by at least an order of magnitude and have a molecular weight between 1 kDa to 1000 kDa. Ultrafiltration membranes can be used to either purify the filtrate (solution passed through the filter) or collect the retentate (material retained by the filter).

Ultrafiltration is typically used to:

• Separate proteins from buffer components for buffer exchange, desalting, or concentration
• Remove or exchange sugars
• Remove or exchange non-aqueous solvents
• Separate free and protein-bound ligands
• Remove materials of low molecular weight
• Rapidly change ionic and/or pH environment

Ultrafiltration vs Microfiltration Membranes

Ultrafiltration membranes, including Ultracel^® regenerated cellulose membranes, are membranes that feature two distinct layers (Figure 1):

• a thin (0.1-1.5 µm), dense skin with a pore diameter of 10-400 angstroms
• highly porous substructure

In contrast to the porous substructure, the dense cellulose-based skin allows for precise molecular weight cut-offs (MWCO) due to its highly controlled and precise pore size. If particulates are below the MWCO and able to pass through the dense skin layer, they are then able to freely pass through the porous membrane.

Microporous membranes are rigid, continuous meshes of polymeric material with defined pore sizes and are used to retain bacteria, colloids, and particulates (Figure 2). Particles are either retained on the membrane surface or are trapped within its substructure (depth filter).

How to use ultrafiltration in your lab

We offer a variety of ultrafiltration membranes and devices, to ensure we meet the needs of your specific application. Based upon general application criteria and sample properties, our scientists have put together a table to suggest which Amicon^® product would likely be the most suitable for your application. Use the links provided below to learn more about the capabilities of each of our ultrafiltration products.

Still not sure how ultrafiltration could be used in your lab? Check out our ultrafiltration protocols for protein sample preparation to see how you could speed up and improve your sample preparation.