The molecules behind the lessons
Fourteen real structures, solved by crystallography or electron diffraction and deposited in the Protein Data Bank. Rotate them, follow the narration beat by beat, see where the drug sits — and, for the one solved twice, watch the enzyme close. Every model carries its entry, its method and its resolution: this is evidence, not illustration.
An enzyme closing
The only entry here that moves. Two crystal structures of one enzyme — shut on its substrate, and open — with the travel between them measured rather than imagined.
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An enzyme caught shut
Adenylate kinase moves a phosphate between two nucleotides, and it can only do that with both of them held still and water kept out. What is drawn is the enzyme closed around them: a rigid core, and two flaps folded down over the site.
Coordinates from the Protein Data Bank (RCSB), public domain under CC0 1.0. Reduced models: alpha carbons for proteins, phosphorus for DNA, every heavy atom of the ligands.