The use of heavy water (D2O) as a solvent is commonplace in many spectroscopic techniques for the study of biological macromolecules. A significant deuterium isotope effect exists where hydrogen-bonding is important, such as in protein stability, dynamics and assembly. Here we illustrate the use of D2O in additive screening for the production of reproducible diffraction-quality crystals for the Salmonella enteritidis fimbriae 14 (SEF14) putative tip adhesin, SefD. (C) 2012 Elsevier Inc. All rights reserved.