Promoting crystallisation of the Salmonella enteritidis fimbriae 14 pilin SefD using deuterium oxide

► The benefits of D2O in screening for crystallisation was explored. ► The crystal structures of the SefD pilin in both H2O and D2O reveal differences. ► Crystallisation improvements are explained by altered interactions in D2O crystals. ► D2O is useful additive in sparse-matrix screening for crystallisation.