Comparison of key NA-ligand interactions.

All residues are N2 numbered and distances are given in Å. The 4-guanidino group of zanamivir, laninamivir and CS-8958 is abbreviated as ‘4-guan’. Bond distances are based on the distances between oxygen and nitrogen atoms and do not include hydrogen atoms, which cannot be directly observed using X-ray diffraction. Distances are given for molecule A in the asymmetric unit of each structure and are highly consistent between molecules. The distance of the unique hydrogen bond between the laninamivir octanoate 9-ester-O and p09N1 Asn294 is given for both molecules A and B as it varies significantly. Laninamivir octanoate is listed as CS-8958 to save space.*The Asp151 side chain carboxy hydrogen bonds with the 4-N of all the ligands used in this study.**The Asp151 and Trp178 backbone carbonyl groups both hydrogen bond with the 4-guanidino group of zanamivir, laninamivir and laninamivir octanoate.***The laninamivir octanoate 9-ester-carbonyl forms a hydrogen bond with N2 Arg224.所有残基均采用N2编号，距离单位为埃（Å）。扎那米韦（zanamivir）、拉尼米韦（laninamivir）与CS-8958的4-胍基缩写为"4-guan"。键长基于氧原子与氮原子间的距离，未纳入氢原子——因X射线衍射（X-ray diffraction）无法直接观测氢原子。各结构不对称单元内A分子的距离数据在不同分子间高度一致。由于辛酸拉尼米韦（laninamivir octanoate）9-酯氧与p09N1天冬酰胺294（Asn294）之间的特有氢键距离存在显著差异，故分别给出了两个分子（A与B）的对应数据。为节省篇幅，辛酸拉尼米韦（laninamivir octanoate）在本文中以CS-8958指代。 * 天冬氨酸151（Asp151）的侧链羧基与本研究中所有配体的4-N位点形成氢键。 ** 天冬氨酸151（Asp151）与色氨酸178（Trp178）的主链羰基均与扎那米韦（zanamivir）、拉尼米韦（laninamivir）及辛酸拉尼米韦（laninamivir octanoate）的4-胍基形成氢键。 *** 辛酸拉尼米韦（laninamivir octanoate）的9-酯羰基与N2精氨酸224（Arg224）形成氢键。