The much lower adhesion mediated by the 5-repeat DC-SIGNR might at first be unexpected, since the CRDs fold autonomously and appear to be fully functional based on solution binding data and on affinity purification. 20 Hydrodynamic measurements show that this protein forms mixture of interconverting dimers and tetramers. However, some of the 5-repeat DC-SIGNR proteins may not be optimally oriented for binding, and it is possible that the dimers are more prone to unfolding under an applied force. Both factors would reduce the adhesion. The softer repulsion (shallow, repulsive force at D < D C ) is also attributed to the mixture of dimers and tetramers.