Fig. 3.

(a) ¹H-STD-NMR analysis of the interaction of pentasaccharide 29 and hexasaccharide 30 with DC-SIGN based on H1 and H2 protons of the Man residues. Quantification is provided in the Supplementary data (Fig. S3 and S5). Expansion of the ¹H-STD spectra at the Man H1 and H2 regions is shown (ratio lectin (tetramer): ligand = 1:45). Residues are named from A to F starting from the non-reducing-end. (b) NOESY (left, A and B with mixing times 300 ms and 50 ms respectively) and trNOESY (right, C with mixing time 50 ms) spectra of hexasaccharide 30 in the free and DC-SIGN bound states, respectively. Two different regions are shown for every experiment: on top (A.1, B.1 and C.1) the anomeric correlations, and below (A.2, B.2 and C.2) the correlations of the aminopropyl moiety. The NOE cross peaks are labeled: inter-residue (black) and intra-residue (grey). NOE correlation of the free hexasaccharide 30 (left, A.1 and B.1) are negative (blue contours) under the conditions used (see experimental section), except for those of the aminopropyl moiety at the reducing-end (A.2 and B.2, mixed orange/blue contours). NOE correlations are very weak at low mixing times (50 ms, B.1). In the presence of DC-SIGN (ratio lectin-binding-sites: 30 = 1:11) NOE correlations at 50 ms were negative and strong (C.1). Correlations of the –OCH₂CH₂- moiety of the aminopropyl moiety (3.7/1.9 and 3.5/1.9 ppm) were negative (C.2). The carbohydrate sequences are represented according to symbol carbohydrate nomenclature (Neelamegham et al. 2019). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)