the site on Domain B, KD1 and KD2, based on a two binding
site model (Fig. 3b, see Experimental section in ESIw for
details). The data summarized in Table 1 demonstrate that
both GNPs, GNP-M2 and GNP-M3, exhibit an affinity
enhancement by several orders of magnitude compared to
the affinities measured for the isolated, monomeric sugars
interacting with CVNQ50C. Taking into account the number
of ligands on the particles, i.e. considering the affinity/ligand,
an increase up to several hundred times is still present for
the Au NP-bound glycan (Table 1). In addition, GNP-M3
exhibited a higher affinity than GNP-M2 for both domains.
These results correlate well with the general affinity ranking of
the free ligands Man2 and Man3, and are consistent with
observations in our previous study with a different GNP-lectin
system.21 Interestingly, for both GNP-M2 and GNP-M3, the
affinity enhancement is more pronounced for the better binding
domain. For example, Man2 exhibits a higher affinity for the
binding site on Domain B, and with GNP-M2, the affinity
enhancement factor (EF) is 178 for the Domain B site vs. 8.3
for the Domain A site (Table 1). For GNP-M3, on the other
hand, the opposite was observed that the EF is higher for the
Domain A site (340) than for the Domain B site (3.8).
Notes and references
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This work was supported by National Institutes of Health
Grants R01GM080295 and 2R15GM066279 (to M.Y.) and
R01GM080642 (to A.M.G.). L.D. thanks the China Scholarship
Council for a special scholarship award.
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c
8622 Chem. Commun., 2011, 47, 8620–8622
This journal is The Royal Society of Chemistry 2011