1) Protein concentration can be calculated using absorbance assays which measure how much ultraviolet light is absorbed by protein solutions. 2) The Beer-Lambert law states that absorbance is directly proportional to analyte concentration. Proteins absorb UV light with maxima at 280nm and 200nm due to aromatic amino acids and peptide bonds. 3) Serial and doubling dilutions are used to successively decrease the concentration of solutions. Serial dilutions decrease the concentration by the same amount each time while doubling dilutions halve the concentration at each step.