Sathyanarayana B K, Stevens E S
Department of Chemistry, State University of New York, Binghamton 13901.
J Biomol Struct Dyn. 1983 Dec;1(4):947-59. doi: 10.1080/07391102.1983.10507496.
The total potential energy including nonbonded, torsional and hydrogen bond contributions has been computed for pustulan, a (1----6) linked beta-D-glucan polysaccharide, as a function of rotational angles phi, psi, and omega. The (phi,psi,omega)-space contains many local minima and at least three distinct deep minima. Two minima at (phi,psi,omega) = (25 degrees, 190 degrees,gg) and (phi,psi,omega) = 65 degrees, 150 degrees,gg) of almost equal energies have helical parameters (n = 5.2, h = 1.0A) and (n = 3.2, h = 1.5A), respectively. A third minimum at (phi,psi,omega) = (40 degrees, 70 degrees gt) leads to an extended zig-zag structure (n = 2.2, h = 2.2A). Energy maps obtained for gentiobiose, the disaccharide of pustulan, also reveal many local minima and the small energy differences among them indicate that gentiobiose is extremely flexible. Gentiodextrins, a family of cyclic molecules of (1----6)-beta-D-glucose residues, were also studied. Conformations free from steric hindrance were found for cyclic molecules with three to six glucose residues.
已计算出包括非键合、扭转和氢键贡献在内的总势能，该势能是作为旋转角φ、ψ和ω的函数，针对一种(1→6)连接的β-D-葡聚糖多糖——松萝酸聚糖进行计算的。(φ,ψ,ω)空间包含许多局部极小值以及至少三个不同的深极小值。在(φ,ψ,ω) = (25度, 190度, gg)和(φ,ψ,ω) = (65度, 150度, gg)处的两个几乎等能量的极小值分别具有螺旋参数(n = 5.2, h = 1.0埃)和(n = 3.2, h = 1.5埃)。在(φ,ψ,ω) = (40度, 70度, gt)处的第三个极小值导致一种伸展的之字形结构(n = 2.2, h = 2.2埃)。对松萝酸聚糖的二糖——龙胆二糖获得的能量图也揭示了许多局部极小值，并且它们之间的小能量差异表明龙胆二糖具有极大的灵活性。还研究了龙胆糊精，这是一族由(1→6)-β-D-葡萄糖残基组成的环状分子。对于含有三到六个葡萄糖残基的环状分子，发现了无空间位阻的构象。
