Albumins and Transport Proteins

Bovine Serum Albumin (BSA)

• Chromatographic purification of albumin typically yields a more highly conserved native protein conformation than the ethanol and heat shock fractionation methods.
• The ethanol and heat shock method combine both processes using Cohn fractionation to perform the initial purification followed by a heat step to further purify the albumin to ≥ 99% by Agarose electrophoresis.
• Ethanol fractionation is a fractionation method that includes the adjustment of ethanol concentration, pH, and temperature. Unlike the heat shock method, this process is kept at a low temperature ensuring a non-denaturing condition for the proteins and preserves the native albumin structure and function.
• The heat shock fractionation process of heat and pH adjustment relies on the addition of a protein stabilizer. This addition allows the albumin to tolerate the increased temperature of > 65 °C. Most other plasma proteins denature and precipitate during this process yielding an albumin with increased purity.

Human Serum Albumin (HSA)

Human serum albumin (HSA) is the most abundant protein in human plasma with a molecular weight of ~66 kDa (based on amino acid composition). Serum albumin may be referred to as Cohn Fraction V. This naming convention is taken from the original Cohn method of fractionating serum proteins using cold ethanol precipitation, as serum albumin was found in the fifth ethanol fraction using Cohn’s method. Since then, the term "Cohn Fraction V" has been used by some to describe serum albumin regardless of the method of preparation. We produce human serum albumins using a cold alcohol fractionation process derived from the traditional Cohn method, as well as from the heat shock method, and offer both native and recombinant versions of HSA in powder and solution formats.

Other Albumin Products

Our portfolio includes additional albumin products for specific applications requiring human and other nonbovine proteins. Recombinant human albumins and animal component-free (ACF) albumin are supplied in aqueous buffers or lyophilized powder formats. Albumins available from other species include those derived from the following sources:

• chicken egg white
• mouse serum
• rat serum
• porcine serum
• ovine serum

Our albumins are of high purity and superior solubility to ensure low background in protein quantitation assays, and to minimize interference in bioprocesses.

Transferrins and Transferrin Replacements

Cells require iron to bind available oxygen from the extracellular environment. Transferrins are single chain glycoproteins found in serum that facilitate the uptake of iron in culture medium and its subsequent intracellular transport.  Although transferrin is the physiologically optimal method for delivering iron to cells in culture and has therefore been integral in the production of biopharmaceuticals such as monoclonal antibodies, lower-risk animal-free systems have led to some adoption of small-molecule alternatives to transferrin in biomanufacturing. Many of these transferrin alternatives are iron chelators, which must be used with appropriate protocols in culture systems as many do not manage redox cycling of iron and can therefore contribute to oxidative stress.  Our cell culture reagents include a complete selection of transferrins and transferrin replacements.