Yui T, Nabekura T, Ogawa K
Faculty of Engineering, Miyazaki University, Japan.
Carbohydr Res. 1997 Nov 28;304(3-4):341-5. doi: 10.1016/s0008-6215(97)00235-8.
Possible regular helix models of beijeran, a new acidic heteropolysaccharide consisting of a trisaccharide as a repeating unit, were investigated. Conformational analyses of the three component disaccharides were first carried out by calculating their relaxed-residue energy maps with respect to the glycosidic bond rotations, phi and psi. A search for possible beijeran chain conformations was carried out by calculating the two-dimensional map of the helix parameters; n (the number of asymmetric units per a fiber repeat) and h (the axial rise per the unit), on the basis of the phi-psi conformations taken from the low energy regions of each of the three energy maps. The n-h values of the helix models with low steric energies were mostly found to be around the experimental values (n = 2 and h = 1.20-1.25 nm), which may support the present methodology. It was also suggested that the internal flexibility of beijeran chain allowed it to conform in diverse helical structures, each of which were reasonably in accord with the observed n-h values. The three representative helix models were finally proposed for the beijeran chain conformation in the crystal structure.
对一种新的酸性杂多糖——贝吉聚糖（beijeran）的可能规则螺旋模型进行了研究，该杂多糖由三糖作为重复单元组成。首先通过计算三种组成二糖相对于糖苷键旋转角度φ和ψ的松弛残基能量图，对其进行构象分析。基于从三个能量图的低能量区域获取的φ-ψ构象，通过计算螺旋参数（n，每一个纤维重复单元中的不对称单元数；h，每一个单元的轴向上升）的二维图，来寻找贝吉聚糖链可能的构象。大部分具有低空间位阻能的螺旋模型的n-h值都在实验值（n = 2，h = 1.20 - 1.25 nm）左右，这可能支持了当前的方法。还表明贝吉聚糖链的内部柔韧性使其能够呈现出多种螺旋结构，每一种结构都与观察到的n-h值合理相符。最后针对晶体结构中的贝吉聚糖链构象提出了三种代表性的螺旋模型。
