I have a protocol for testing non structural proteins (with Bradford) and I was told there is a similar one for structural protein. Also, I would like to hear generally about what is used for free protein and cell wall protein.
you can try the protocol below. We have used it for animal total homogenates.
"Protein in sample homogenates was determined by a modification of a CBB-based method. Specifically, 0.063 ml of various dilutions of the homogenate was mixed with 0.02 ml 0.5% (v/v) Triton X-100 and 0.017 ml 6 N HCl. The mixture was incubated at 100°C for 10 minutes, brought to room temperature, and mixed with 0.9 ml 0.033% (w/v) CBB-G250 stock reagent (made in 0.5 N HCl, stirred for 30 minutes, and filtrated through Whatman #1 filter paper by water pump aspiration, and stored in the dark) and incubated for 5 minutes at room temperature. The absorbance at 620 nm of the mixture was converted to protein mg from a 0–0.05 mg BSA standard curve, by using appropriate sample and reagent blanks. Sample blanks are mixed with 0.9 ml 0.5 N HCl and reagent blanks contain 0.063 ml of the homogenation buffer"