Which of the following methods can be used for measuring protein concentration in biological samples? (Select all that apply)

Protein concentration in biological samples can be measured with several common laboratory methods. The Bradford assay uses a dye that binds to proteins, the Lowry method relies on a color change after reacting with copper ions, and the bicinchoninic acid (BCA) assay also produces a colored product that can be read by a spectrophotometer. A simple UV absorption measurement at 280 nm takes advantage of the fact that aromatic amino acids absorb light at this wavelength, allowing a quick estimate of protein amount. Finally, an enzyme‑linked immunosorbent assay (ELISA) can quantify specific proteins with high sensitivity. Each of these approaches works well for different sample types and desired accuracy.