ΔG: -11.8 kcal/mol.
Second candidate: a quinoline ring with a tail of fluorine atoms. Vina rotated bonds systematically: torsional angles flipping like pages in a silent book. It found a shallow groove, but not the pocket. ΔG: -7.1.
Aris wanted to say: Neither does Vina. Neither does the protein. The universe doesn't know why things stick together—it just does. And then we call it affinity.
Aris sat up. That was near-covalent strength. Non-covalent binding didn't get much better.
On screen, the small molecule tumbled end over end—a benzofuran derivative with a nitrogen spike. Vina calculated the free energy of binding: ΔG. Negative numbers were good. -6.2 kcal/mol. Not great.
Aris nodded. "We need a molecule small enough to crawl inside that pocket and stubborn enough to stay."
He fed it the 3D structure of the protein—a PDB file full of atomic coordinates, each carbon and nitrogen a node in a silent scaffold. Then he defined the search space: a 3D box, 20 angstroms on each side, centered on the hydrophobic pocket.
That, Aris thought, is the real story of 3D Vina. Not the software. The seeing . The act of turning a disease into a shape, and that shape into a key, and that key into a cure—all inside a ghost made of math.
The molecule kissed the protein's surface and bounced off.
Why? Because evolution had built proteins to be sticky in predictable ways. The energy landscape was not random. It had deep basins that Vina's crude Monte Carlo method could find. That night, Aris ran a blind docking experiment. He gave Vina a protein with no known ligands—an orphan receptor from a deep-sea bacterium. He set the search box to cover the entire surface.