Taking advantage of the known planarity of the N‐acetyl group of N‐acetylglucosamine, an analysis of the quality of carbohydrate structures found in the protein databank was performed. Few obvious defects of the local geometry of the carbonyl group were observed. However, the N‐acetyl group was often found in the less favorable cis conformation (12% of the cases). It was also found severely twisted in numerous instances, especially in structures with a resolution poorer than 1.9 Å determined between 2000 and 2015. Though the automated PDB‐REDO procedure has proved able to improve nearly 85% of the structural models deposited to the PDB, and does prove able to cure most severely twisted conformations of the N‐acetyl group, it fails to correct its high rate of cis conformations. More generally, for structures with a resolution poorer than 1.6 Å, it produces N‐acetylglucosamine models in slightly poorer agreement with experimental data, as measured using real‐space correlation coefficients. Significant improvements are thus still needed, at least as far as this carbohydrate structure is concerned.

中文翻译：

---

在蛋白质数据库中发现了许多严重扭曲的N-乙酰氨基葡萄糖构象。

利用已知的N-乙酰氨基葡萄糖N-乙酰基平面性，对蛋白质数据库中发现的碳水化合物结构进行了质量分析。几乎没有观察到羰基局部几何形状的明显缺陷。但是，通常以较不利的顺式构象发现N-乙酰基（占病例的12％）。还发现它在许多情况下都发生了严重扭曲，特别是在2000年至2015年间确定的分辨率低于1.9Å的结构中。尽管PDB-REDO自动化程序已证明能够改善将近85％的结构模型沉积到PDB中，并确实能够治愈N-乙酰基团最严重扭曲的构象，但无法纠正其高顺式发生率构象。通常，对于分辨率低于1.6Å的结构，使用实空间相关系数测得的N-乙酰氨基葡糖模型与实验数据的一致性稍差。因此，至少就这种碳水化合物结构而言，仍然需要显着的改进。