TheBCSScreenHT-96EcoScreenMD1-105-ECO
TheBCS(BasicChemicalSpace)ScreendevelopedattheStructuralGenomicConsortium(SGC),Oxfordhasanovelapproachtoscreening.PEGsaregroupedbymolecularweightandmixedtocreatefourPEGSmears(availabletopurchaseseparately).TheSmearscoverabroaderrangeofchemicalspacewhilereducingthenumberofPEGvariables.
ThisisanEcoHT-versionofthisinnovativescreen,wheresodiumcacodylatehasbeenreplacedbyMES.
PEGisaneffectivecrystallizationagentduetoitsprotein-proteininteractionpromotingproperties.TheBIOLOGicalMacromolecularCrystallizationdatabaserecordsatleast20differentPEGcompoundsinfrequentuseasmacromolecularprecipitants.TheBCSscreenovercomestheimpracticalityofsamplingallPEGvarietiesthathasledtoafewvariantspredominatinginthemostcommonscreens(right).
ThebottomlineisthatintestsattheSGCwith191humanproteins,TheBCSScreenhada42%hitratewithonly96conditions.Manyoftheseproteinshadfailedtocrystallizeinotherscreens.
Thefirst24conditionsinTheBCSScreenformagridscreenofthefourPEGSmearsagainstpH(range4.5-9.5).Theremaining72conditionsconsistofasparsematrixscreeninwhichtheprecipitantisalwaysoneofthePEGSmearsbutwithavarietyofadditivesandbuffers.Theadditivesincludesomeofthemoreunusualcrystal-promotingagentssuchasrubidiumchloride(alsousefulforphasing)andammoniumnitrate.Morecommonadditivesincludingsodiumbromide(usefulforphasing)andglycerolarealsousedinthescreen.
Reference
Chaikuad,A,Knapp,SandvonDelft,K(2015).DefinedPEGsmearsasanalternativeapproachtoenhancethesearchforcrystallizationconditionsandcrystal-qualityimprovementinreducedscreens.ActaCrystallographicaF71:1627-1639.