Frequency responses (phase and modulation) of Human Serum Albumin (HSA). The excitation source was a 300-nm LED, T = 20°C; the emission was collected through a WG 320 high-pass filter. The data is best fitted by a Lorentzian distribution (peak = 5.4 ns, width = 2.9 ns, fractional distribution = 98%) and a second discrete component (τ = 0.51 ns and fractional contribution = 0.02%).