Fig. 3. NP heating power determines a window for targeted denaturation. (A) D₂/D₁ in terms heating power (g) with a 1 μs excitation duration and a 9 NP μm⁻² area density. Three major stages for protein denaturation as g increases: stage I, uniformly no denaturation zone with high D₂/D₁ (1–100%); stage II, targeted denaturation window with low D₂/D₁ (<1%); stage III, widespread denaturation with high D₂/D₁ (1–100%). g₁ and g₂ are critical heating powers that separate the three stages. (B) D₂/D₁ in terms of g with different combinations of excitation durations and NP area densities. (C) D₁ in terms g with a 1 μs excitation duration and a 9 μm⁻² area density. Here we define a critical heating power g₃ that corresponds D₁ = 50%. (D) D_total in terms g with a 1 μs excitation duration and a 9 μm⁻² area density. We define a critical heating power g₄ that corresponds D_total = 5%. (E) Schematic for g₁, g₂, g₃, and g₄.