Delbaere L T
Biochem J. 1974 Oct;143(1):197-205. doi: 10.1042/bj1430197.
X-ray analyses have shown that the glucopyranose rings of GlcNAc-Asn [4-N-(2-acetamido-2-deoxy-beta-d-glucopyranosyl)-l-asparagine] and Glc-Asn [4-N-(beta-d-glucopyranosyl)-l-asparagine] both have the C-1 chair conformation and also that the glucose-asparagine linkage of each molecule is present in the beta-anomeric configuration. The dimensions (the estimated standard deviations of the last digit are in parentheses) of the glycosidic bond in GlcNAc-Asn and Glc-Asn are, respectively, C((1))-N((1)) 0.1441(6)nm, 0.146(2)nm; angle O((5))-C((1))-N((1)) 106.8(3) degrees , 105.7(8) degrees ; angle C((2))-C((1))-N((1)) 111.1(4) degrees , 110.4(9) degrees ; angle C((1))-N((1))-C((9)) 121.4(4) degrees , 120.5(9) degrees . The glycosidic torsion angle C((9))-N((1))-C((1))-C((2)) is 141.0 degrees and 157.6 degrees in GlcNAc-Asn and Glc-Asn respectively. Hydrogen-bonding is extensive in these two crystal structures and does affect one torsion angle in particular. Two very different values of chi(1)(N-C(alpha)-C(beta)-C(gamma)) occur for the asparagine residue of the two different molecules; the values of chi(1), -69.0 degrees in GlcNAc-Asn and 61.9 degrees in Glc-Asn, correspond to two different staggered conformations about the C(alpha)-C(beta) bond as the NH(3) (+) group is adjusted to different hydrogen-bonding patterns. The two trans-peptide groups in GlcNAc-Asn show small distortions in planarity whereas that in Glc-Asn is more non-planar. The mean plane through the atoms of the amide group at C((2)) in GlcNAc-Asn is approximately perpendicular (69 degrees ) to the mean plane through the C((2)), C((3)), C((5)) and O((5)) atoms of the glucose ring and that at C((1)) is less perpendicular (65 degrees ). The mean plane through the atoms of the amide group in Glc-Asn makes an angle of only 55 degrees with the mean plane through these same four atoms of the glucose ring. The N((1))-H bond of the amide at C((1)) is trans to the C((1))-H bond in these two compounds; the N((2))-H bond of the amide at C((2)) is trans to the C((2))-H bond in GlcNAc-Asn. The values of the observed and final calculated structure amplitudes have been deposited as Supplementary Publication SUP 50035 (26 pages) at the British Library (Lending Division), (formerly the National Lending Library for Science and Technology), Boston Spa, Yorks. LS23 7BQ, U.K., from whom copies may be obtained on the terms given in Biochem. J. (1973) 131, 5.
X射线分析表明，N-乙酰葡糖胺-天冬酰胺[4 - N -（2 - 乙酰氨基 - 2 - 脱氧 - β - D - 吡喃葡糖基）- L - 天冬酰胺]和葡萄糖-天冬酰胺[4 - N -（β - D - 吡喃葡糖基）- L - 天冬酰胺]中的吡喃葡萄糖环均具有C - 1椅式构象，并且每个分子的葡萄糖-天冬酰胺键均以β - 异头构型存在。N - 乙酰葡糖胺-天冬酰胺和葡萄糖-天冬酰胺中糖苷键的尺寸（括号内为最后一位数字的估计标准偏差）分别为：C(1)-N(1) 0.1441(6)nm，0.146(2)nm；角度O(5)-C(1)-N(1) 106.8(3)°，105.7(8)°；角度C(2)-C(1)-N(1) 111.1(4)°，110.4(9)°；角度C(1)-N(1)-C(9) 121.4(4)°，120.5(9)°。在N - 乙酰葡糖胺-天冬酰胺和葡萄糖-天冬酰胺中，糖苷扭转角C(9)-N(1)-C(1)-C(2)分别为141.0°和157.6°。在这两种晶体结构中广泛存在氢键，并且确实特别影响了一个扭转角。两种不同分子中天冬酰胺残基的χ1（N - Cα - Cβ - Cγ）出现两个非常不同的值；χ1的值，在N - 乙酰葡糖胺-天冬酰胺中为 - 69.0°，在葡萄糖-天冬酰胺中为61.9°，对应于随着NH3(+)基团调整为不同的氢键模式，围绕Cα - Cβ键的两种不同的交错构象。N - 乙酰葡糖胺-天冬酰胺中的两个反式肽基在平面性上有小的扭曲，而葡萄糖-天冬酰胺中的那个则更不平面。通过N - 乙酰葡糖胺-天冬酰胺中C(2)处酰胺基团原子的平均平面与通过葡萄糖环的C(2)、C(3)、C(5)和O(5)原子的平均平面近似垂直（69°），而在C(1)处的则不太垂直（65°）。通过葡萄糖-天冬酰胺中酰胺基团原子的平均平面与通过葡萄糖环的这相同四个原子的平均平面仅成55°角。在这两种化合物中，C(1)处酰胺的N(1)-H键与C(1)-H键反式；在N - 乙酰葡糖胺-天冬酰胺中，C(2)处酰胺的N(2)-H键与C(2)-H键反式。观察到的和最终计算出的结构振幅值已作为补充出版物SUP 50035（26页）存放在英国图书馆（借阅部）（原国家科学技术借阅图书馆），波士顿温泉，约克郡，LS23 7BQ，英国，可按《生物化学杂志》（1973年）131卷，5期给出的条件从该处获取复印件。
