Practice question

PALM utilizes genetically encoded photoactivatable fluorescent proteins like mEos and Dronpa. Initially dark proteins are sparsely photoactivated by low-intensity violet light, imaged, then photobleached, ensuring only few molecules emit simultaneously. Gaussian fitting of each spot provides ~20 nm localization precision. Repeating this activation-imaging cycle builds a super-resolved map from thousands of localizations. Achieving 10-30 nm resolution, PALM is particularly suited for live-cell studies of molecular clustering, because photoactivatable proteins can be fused endogenously and tracked in quantitative single-molecule counting experiments.