DETERGENT INTERFERENCE WITH LOWRY ASSAY OF BOVINE-MILK FAT GLOBULE-MEMBRANE PROTEIN

The interference of Triton X-100, Lubrol PX, and Zwittergent 3-14 dete rgents with the determination of bovine milk fat globule membrane prot ein by the Lowry protein assay was examined. In the concentration rang e of 0.5 to 2.0% (w/v), all three detergents caused concentration-depe ndent overestimates of protein content of both bovine serum albumin an d bovine milk fat globule membrane samples. This detergent concentrati on range is an important operational concentration range for the solub ilization of membrane proteins. When sodium dodecyl sulfate (SDS) was added to yield a 1:1 concentration ratio of SDS:interfering detergent, the overestimates of Lowry protein in the presence of all three deter gents were eliminated.