I dissolved 0.1 mg of β-amyloid (1-42) in 0.1 ml of HFIP. After evaporation of HFIP by speedvac further it was dissolved in 1X PBS buffer (concentration= approximately 22 μM ). But when I was checking the Optical Density (Molar Extinction Coefficient = 1450 at 276 nm) to confirm the actual concentration, I found it 0.15897 which is corresponding to 109.63 μM of β-amyloid. I am also attaching the absorption spectrum of β-amyloid (1-42) which I was observed during my experiment. Please help me in this regard.