MS02-P01 Identification of contaminants with SIMBAD: A Sequence-independent molecular replacement pipeline Adam Simpkin (University of Liverpool, synchrotron SOLEIL, Paris, France) Felix Simkovic (University of Liverpool, Liverpool, United Kingdom) Jens Thomas (University of Liverpool, Liverpool, United Kingdom) Martin Savko (Synchrotron SOLEIL , Paris, France) Charles Ballard (STFC, CCP4, Oxford, United Kingdom) Marcin Wojdyr (STFC, CCP4, Global Phasing, Oxford, United Kingdom) William Shepard (Synchrotron SOLEIL , Paris, France) Daniel Rigden (University of Liverpool, Liverpool, United Kingdom) Ronan Keegan (STFC, CCP4, Oxford, United Kingdom)email: hlasimpk@liv.ac.ukIn protein crystallisation it is not uncommon for contaminant proteins to crystallise instead of the protein of interest. Solving structures with molecular replacement in such cases can be difficult since the search models, assumed to be similar to the protein of interest, are not necessarily related to the proteins that have actually crystallised. SIMBAD is a pipeline to solve crystal structures without prior sequence information that can provide a route to identify the presence of a contaminant in a crystal and lead to structure solution. Early users of SIMBAD have unearthed several examples of unintentional crystallisation of previously known and unknown contaminant proteins. Other successful user cases have highlighted the problem of the mis-identification of crystals, where a mix-up has occurred (e.g. swapped crystallisation trays) and a dataset has been incorrectly assigned as being a different target structure. In all of these cases, mis-directed efforts in attempting to solve the structure of the target crystal could have been avoided through the use of SIMBAD at the point of data collection or through more rigorous annotation and experimental assessment of the crystal prior to data collection.References:

Keywords: SIMBAD, MR, contaminants