Comparative study of Lowry and Bradford methods: interfering substances

The methods of Lowry and Bradford, commonly used for protein determination, were compared regarding the level of interference of some substances used for glucoamylase precipitation by ethanol. The method of Bradford suffers no interference while the method of Lowry showed protein concentration values 20% increased in the presence of ethanol and Tris. Despite these interferences, the Lowry method can evaluate more accurately the increase of purity during fractionation, due to its sensitivity to low molecular weight (below 6 kDa) proteins and peptides.