Binding of CCL2 wild-type to different carbohydrates and CCL2 variants to GlcNAcβ1,4[Fucα1,3]GlcNAcβ1-sp (sp: spacer O-[CH2]5COOH) measured with isothermal titration calorimetry and NMR spectroscopy at 299K.

and: not determined.bThe increased affinity of N91A might be an artifact caused by interaction of the artificial carbohydrate spacer O-(CH2)5-COOH with residue 91. Whereas the spacer might sterically clash with N91, Ala in this position could form favorable van-der-Waals interactions. In the case of natural N-glycans, where the reducing GlcNAc is linked to Asn of a glycoprotein projecting away from CCL2 (upper right corner of Figure 5D), Asn is likely to be favored at this position of CCL2 due to the potential formation of H-bonds.且：尚未确定。N91A突变体的亲和力升高现象，可能是人工碳水间隔基O-(CH2)5-COOH与91号残基相互作用所导致的人为假象。该间隔基或与91位天冬酰胺(Asn)发生空间位阻，而替换为丙氨酸(Ala)后则可形成有利的范德华相互作用。在天然N-聚糖(N-glycans)的情境中，还原性N-乙酰葡糖胺(GlcNAc)连接至糖蛋白的天冬酰胺(Asn)，该糖蛋白从CCL2分子向外伸展，对应图5D右上角区域，此时CCL2的该位点更倾向于保留天冬酰胺，因其可形成潜在的氢键(H-bonds)。