The characterization of weak protein-protein interactions: Evidence from DEER for the trimerization of a von Willebrand factor A domain in solution

(Figure Presented) Distance determination: A double electron electron resonance (DEER) measurement of a distance of 6.1 nm (green lines) between singly nitroxide-labeled human von Willebrand Factor A domains demonstrates oligomerization of this domain in dilute solution (see structure); probably in an arrangement similar to that observed in the crystal structure. The DEER technique should be generally applicable for characterizing noncovalent interactions between macromolecules in solution. © 2006 Wiley-VCH Verlag GmbH & Co. KGaA.