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Science 26 October 2007:
Vol. 318. no. 5850, pp. 619 - 622
DOI: 10.1126/science.1148735
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Reports

A Synthetic Lectin Analog for Biomimetic Disaccharide Recognition

Yann Ferrand, Matthew P. Crump and Anthony P. Davis*

School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK.


Figure 1 Fig. 1. The design of receptors for all-equatorial carbohydrates. (Top) ß-D-Glucose 1 and complementary receptor framework 2. Polar and hydrophobic moieties are shown in red and blue, respectively. X can be varied to control solubility. Versions of 2 are described in (19–21). (Bottom) Disaccharide receptor 3, reported herein, and cellobiose 4, an intended substrate. The roof and floor of 3 are provided by meta-terphenyl units (blue). There are five isophthalamide pillars, two at either end (red) and one located centrally (magenta). The water-solubilizing tricarboxylate units are shown in green. The molecule has two planes of symmetry, one lying parallel to and between the terphenyls, and the other passing through the central (magenta) isophthalamide. [View Larger Version of this Image (30K GIF file)]
 

Figure 2 Fig. 2. Evidence for complex formation between receptor 3 and cellobiose 4. (A) Partial 1H NMR spectra from the addition of 4 to 3 in D2O. The signals shown are due to receptor aromatic protons. The concentration of 3 = 0.5 mM. (B) ICD caused by the addition of 4 (0 to 7 mM) to 3 (0.25 mM). {lambda}, wavelength. (C) Increase in fluorescence output caused by the addition of 4 (0 to 9 mM) to 3 (0.01 mM). CPS, countsper second. (D) Analysis of data from (C) by nonlinear least-squares curve fitting, assuming 1:1 binding stoichiometry. Ka = 560 M–1, limiting {Delta}CPS = 320 CPS. Observed and calculated points are almost coincident. [View Larger Version of this Image (27K GIF file)]
 

Figure 3 Fig. 3. (Top) NOESY contacts observed for the complex between ß-cellobiose and receptor 3. (Bottom) A computational model of the complex, consistent with the NOE data. Water-solubilizing side chains are omitted for clarity. The cellobiose is colored pink, and the terphenyl units are shown in space-filling mode. Polar interactions are represented as dotted lines. Black, carbon; red, oxygen; blue, nitrogen; and white, hydrogen. [View Larger Version of this Image (40K GIF file)]
 

Figure 4 Fig. 4. Carbohydrate substrates used with receptor 3 (in addition to cellobiose 4). For binding results, see Table 1. Me, methyl; Ac, acetyl. [View Larger Version of this Image (21K GIF file)]
 

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