The Phase Problem: Solving Structures | Crystallography 2.11

No lens can focus X-rays, so a detector records only spots, and each spot's brightness gives the length of the structure-factor arrow but not its direction, the phase. This final episode shows that the electron density is a Fourier sum of the spots and that wrong phases give a wrong picture. It then follows three keys that win the phases back: Patterson's map of interatomic vectors, Hauptman and Karle's direct methods, and refinement judged by the R factor, with a nod to Hodgkin and Photograph 51, before drawing all twenty-two episodes on one map. Chapters 0:00 A microscope without a lens 0:22 The lost phase 1:15 Patterson to Hauptman and Karle 1:45 Density as a sum of waves 2:50 Right brightness, wrong phases 3:19 Key one: the Patterson map 4:05 Where the Patterson map gets stuck 4:26 Key two: direct methods 5:10 Key three: refinement and the R factor 5:51 Hodgkin and Photograph 51 6:21 Solving a new crystal, step by step 6:38 Twenty-two episodes on one map 7:35 Three things to take away Reference: M. Martínez-Ripoll (with the late F. Hernández Cano), Crystallography-Cristalografia, web course (CSIC, CC BY-NC 4.0, https://www.xtal.iqf.csic.es/Cristalo..., and university crystallography and diffraction lecture notes. Historical sources: Hauptman and Karle, Nobel Prize in Chemistry 1985, press release: https://www.nobelprize.org/prizes/che... · Hodgkin, Nobel Prize in Chemistry 1964, biographical: https://www.nobelprize.org/prizes/che... · King's College London, The story behind Photograph 51: https://www.kcl.ac.uk/the-story-behin... · Patterson, A Fourier series method for the determination of the components of interatomic distances in crystals, Phys. Rev. 46, 372 (1934): https://doi.org/10.1103/physrev.46.372 · Franklin and Gosling, Molecular configuration in sodium thymonucleate, Nature 171, 740 (1953): https://doi.org/10.1038/171740a0 · Cochran and Woolfson, Have Hauptman and Karle solved the phase problem?, Acta Cryst. 7, 450 (1954): https://doi.org/10.1107/s0365110x5400... Previous episode: 2.10 "Real Peaks". This is the season two finale. Narration: AI voice (ElevenLabs); music: AI-generated (Lyria) and original synthesized tracks.