The affinity of these multivalent compounds of higher molecular mass and with a high avidity was evaluated by direct interaction (SPR) using a recently developed method to generate oriented surfaces where CLRs are presented in a way mimicking the cell surface presentation of receptors . The results of these interaction tests are shown in Figure . Dimerization of Man79 and Man84 ligands on the rod-like scaffold appears to be very efficient and significantly improves the affinity towards the lectins (Table ). For Man79, which is a weak non selective binder of both CLRs (IC50 318µM and 278µM for DC-SIGN and L-SIGN, respectively, Table entry 1 and Figure ) the affinity increases by an order of magnitude in the dimers PM68 (Table , entry 2) and PM70 (Table , entry 3), for both lectins and independent of the length of the flexible linker. Similarly, the dimers of Man84, PM69 and PM74 (Table , entry 5 and 6) bind to DC-SIGN in the low µM range, with an increase by up to 2 orders of magnitude relative to the monovalent spearhead (10 µM and 31 µM, respectively). The same two dimers display an apparent KD of 52 nM (PM69) and 25 nM (PM74) for L-SIGN, confirming a strong effect of the dimerization on the affinity (β-factor 43 of 125 and 250, respectively) and achieving an impressive selectivity for L-SIGN vs. DC-SIGN, that reaches 3 orders of magnitude with the long linker dimer PM74. The effect of selectivity is almost 10 times lower for short linker PM69 (192 for "short" PM69 and 1200 for "long" PM74), clearly suggesting that distance matters.