In what way does a constituent in a condensate exhibit distinctive FRAP behavior compared to a constituent in cytoplasm, organelle, or membrane?

In condensates, molecules show restricted yet dynamic mobility that reflects liquid-like phase behavior, distinct from diffusion in other compartments:

• Cytoplasm: Diffusion is largely unrestricted and FRAP recovery is fast and complete (milliseconds–seconds) because molecules move freely in solution.
• Membranes: Lateral diffusion is 2-D confined; FRAP recovery depends on membrane viscosity and often reaches full recovery but more slowly.
• Organelles (e.g., nucleus, mitochondria): Movement may be hindered by crowding or compartment boundaries, producing slower but still complete recovery.
• Condensates: Molecules display partial and slower recovery. A rapid initial phase reflects exchange of mobile molecules, followed by an incomplete plateau indicating an immobile or stably bound fraction. This biphasic curve and high viscosity reveal liquid-to-gel or solid-like states and weak multivalent interactions that define condensate material properties.