Landersjö Clas, Jansson Jennie L M, Maliniak Arnold, Widmalm Göran
Department of Organic Chemistry and Division of Physical Chemistry, Arrhenius Laboratory, Stockholm University, S-106 91 Stockholm, Sweden.
J Phys Chem B. 2005 Sep 15;109(36):17320-6. doi: 10.1021/jp052206y.
The conformational preference of the human milk oligosaccharide lacto-N-neotetraose, beta-d-Galp-(1 --> 4)-beta-d-GlcpNAc-(1 --> 3)-beta-d-Galp-(1 --> 4)-d-Glcp, has been analyzed using (1)H,(1)H T-ROESY and (1)H,(13)C trans-glycosidic J coupling experiments in isotropic solution and (1)H,(13)C residual dipolar couplings (RDCs) obtained in lyotropic liquid crystalline media. Molecular dynamics simulations of the tetrasaccharide with explicit water as the solvent revealed that two conformational states are significantly populated at the psi glycosidic torsion angle, defined by C(anomeric)-O-C-H, of the (1 --> 3)-linkage. Calculation of order parameters, related to the molecular shape, were based on the inertia tensor and fitting of experimental RDCs to different conformational states showed that psi(+) > 0 degrees is the major and psi(-) < 0 degrees is the minor conformation in solution, in complete agreement with a two-state analysis based on the T-ROESY data. Attention was also given to the effect of salt (200 mM NaCl) in the anisotropic medium, which was a ternary mixture of n-octyl-penta(ethylene glycol), n-octanol, and D(2)O.
已通过在各向同性溶液中进行的¹H,¹H T-ROESY和¹H,¹³C反式糖苷键J耦合实验以及在溶致液晶介质中获得的¹H,¹³C剩余偶极耦合（RDC），分析了人乳寡糖乳糖-N-新四糖β-d-半乳糖基-(1→4)-β-d-葡萄糖胺基-(1→3)-β-d-半乳糖基-(1→4)-d-葡萄糖的构象偏好。以水为溶剂对该四糖进行的分子动力学模拟显示，在由(1→3)连接的C（异头碳）-O-C-H定义的ψ糖苷扭转角处，两种构象状态显著存在。基于惯性张量计算与分子形状相关的序参数，并将实验RDC拟合到不同构象状态，结果表明在溶液中ψ(+)>0°是主要构象，ψ(-)<0°是次要构象，这与基于T-ROESY数据的双态分析完全一致。还关注了在由正辛基五（乙二醇）、正辛醇和D₂O组成的三元混合物的各向异性介质中盐（200 mM NaCl）的影响。
