Progress in low-resolution ab initio phasing with CrowdPhase
- Univ. of California, Los Angeles, CA (United States)
Ab initio phasing by direct computational methods in low-resolution X-ray crystallography is a long-standing challenge. A common approach is to consider it as two subproblems: sampling of phase space and identification of the correct solution. While the former is amenable to a myriad of search algorithms, devising a reliable target function for the latter problem remains an open question. Here, recent developments in CrowdPhase, a collaborative online game powered by a genetic algorithm that evolves an initial population of individuals with random genetic make-up (i.e. random phases) each expressing a phenotype in the form of an electron-density map, are presented. Success relies on the ability of human players to visually evaluate the quality of these maps and, following a Darwinian survival-of-the-fittest concept, direct the search towards optimal solutions. While an initial study demonstrated the feasibility of the approach, some important crystallographic issues were overlooked for the sake of simplicity. To address these, the new CrowdPhase includes consideration of space-group symmetry, a method for handling missing amplitudes, the use of a map correlation coefficient as a quality metric and a solvent-flattening step. Lastly, performances of this installment are discussed for two low-resolution test cases based on bona fide diffraction data.
- Research Organization:
- Univ. of California, Los Angeles, CA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Biological and Environmental Research (BER)
- Grant/Contract Number:
- FC02-02ER63421
- OSTI ID:
- 1345574
- Journal Information:
- Acta Crystallographica. Section D. Structural Biology, Vol. 72, Issue 3; ISSN 2059-7983
- Publisher:
- IUCrCopyright Statement
- Country of Publication:
- United States
- Language:
- English
Web of Science
Similar Records
CrowdPhase: crowdsourcing the phase problem
Identifying the Minimum-Energy Atomic Configuration on a Lattice: Lamarckian Twist on Darwinian Evolution