Here we show that the widely used Bicinchoninic Acid (BCA) assay tends to underestimate protein concentrations of tissue samples.  This method is simple, rapid, more reliable than the BCA assay, compatible with biological samples lysed in RIPA or 2x SDS gel-loading buffer, and also inexpensive.
BCA
We present a Ponceau S staining-based dot-blot assay as an alternative for protein quantification. 
Ponceau S staining-based dot-blot assay