Supplement To:
Parametrization of the GROMOS Force Field for
Oligosaccharides and Assessment of the Efficiency of
Molecular Dynamics Simulations
KarlHeinz Ott1 and Bernd Meyer2
Complex Carbohydrate Research Center and Departments of Biochemistry and Chemistry, The University of Georgia, 220 Riverbend Rd., Athens, GA 30602, USA
Present Addresses:
Cluster analysis:
A complete, hierarchical clustering algorithm1,2 was used to group the
conformations that were represented by sine and cosine values of selected dihedral angles. For run w60, a four dimensional conformational space was defined by the and angles and by two intraring dihedral angles (O5C1C2C3) that are characteristic for the ring conformations. The statistical data analysis package BLSS3 was used to generate the cluster tree for the conformations observed in 300
1 J.A. Hartigan, Clustering Algorithms, Wiley, New York, 1975. 2 B.Everitt, Cluster Analysis, Halsted, New York, 1980.
3 D.M. Abraham and F. Rizzardy, The Berkley Interactive Statistical System, Norton, NY 1988.
Run w
The data set was split into 6 clusters, each having a correlation coefficient of its associated conformations of between 0.3 and 0.7 (Tab. SII). The highest populated cluster with a population of 32% has a gg conformation in the reducing ring and a
gt conformation in the nonreducing ring with the glycosidic linkage at 40o/40o.
Another highly populated cluster with 22% population has the same conformations of the hydroxymethyl groups but has and at 0o. The same glycosidic linkage
conformation with both hydroxymethyl groups in a gg conformation is found in another cluster with 11% population. 24% of the conformations form a cluster that has average and angles of 30o which are the angles found in Xray crystal
close to the global minimum. Only 18% of the conformers have both hexose rings in the 4C1 orientation. In 64% of the simulation either the reducing or the nonreducing ring has the inverted 1C
4 ring conformation. In 17% of the simulation
both rings adopted the 1C4 conformation.
The cluster analysis revealed that the accessible range of the glycosidic linkage space is significantly dependent on the ring conformations. 4C
1 conformers restrict
the conformational flexibility of the glycosidic linkage compared to the 1C4 conformers. The strongest effect is found when comparing the conformational space accessible to the 1C41C4 species with that of the 4C14C1 species (Fig. 1a,d). The position and size of the global minimum of the 4C
14C1 conformers is similar to
those found in the previously described calculations at 350K and 400K. The additional conformational flexibility apparent from the conformational space totally accesses at 600K (Fig. 1, hatched area) originates from a glucose in an inverted 1C
4
conformation (Fig. 1bd). When the nonreducing residue is in a 1C4 conformation, the contour extends to more negative angles (Fig. 1b). In contrary, when the reducing residue adopts a 1C
4 conformation and the nonreducing residue has the 4C
1 conformation the contours extend to more positive values (Fig. 1c). In the
fourth group of clusters, with both rings in the 1C4 conformation, the contour shows the increased flexibility to more negative angles as well as to more positive and angles (Fig. 1d).
Two small clusters show up for the inverted conformation of the glycosidic linkage. This inverted conformer remains stable for about 4 ps while the hexose ring conformations are both in 4C1. Some of the conformers with around 180o
Table S I:
Energy averages of the MD simulations. The total energies (Tot) together with their standard deviations (Std) and the change in the total energy over the entire run (Slp) calculated from a linear regression analysis are given for the MD simulations, wb1, wb2, w, w35, w40, w60 and the in vacuo MD simulations. Additionally, the total kinetic energy (Kin) the total potential Energy (Pot), the electrostatic energy terms for the maltose (Elmalt), for the water (Elwat) and for the maltosewater interaction (Elmw) as well as the corresponding vanderWaals energy terms (LJ malt, LJwat, and LJmw) are listed. The sum of the bond angle and dihedral energies are in column (Bond). The average energy terms for the six MD simulations in water (AVG water), and for the three in vacuo MD simulations (AVG vacuo) are also displayed. ND: not determined.
Run Tot Std Slp Kin Pot Bond EL-malt LJ -malt El-mw LJ -mw El-wat LJ -wat wb1 200ps -14342 177 0 4279 -18621 127 573 -24 -420 -96 -21889 3109 wb2 500ps -14443 178 -129 4273 -18717 46 572 -21 -424 -97 -21904 3111 w 250ps -3741 74 nd 1201 -4942 123 492 -21 -401 -90 -5909 865 w35 200ps -3220 69 14 1353 -4573 137 574 -20 -397 -88 -5556 777 w40 200ps -2704 64 13 1559 -4263 148 573 -20 -371 -90 -5218 715 w60 950ps -1055 64 5 2301 -3356 189 572 -18 -305 -93 -4303 601
va 500ps 589 6 1 68 522 120 420 -18 vb 500ps 591 6 1 68 523 126 414 -16 vc 500ps 670 4 1 68 602 139 480 -18
Avg water -6584 2494 -9078 128 559 -21 -386 -92 -10797 1529 Avg wb -14393 4276 -18669 86 572 -22 -422 -96 -21896 3110 Avg vacuo 617 68 549 128 438 -17
Table SII:
Statistic of the cluster analysis of run w that used sine and cosine values of the , and both dihedral angles as parameters for the cluster definition. The population (Pop) of the six clusters together with their average and angles, their hydroxymethyl group orientation of the reducing (1) and the nonreducing (2) glucose are listed. The last column contains the correlation coefficient (Cor) that are calculated from correlating the vectors defined by the four dihedral angles , and 1,2.
Pop % P 1 2 Cor
806 32 -45 -39 gg-gt 0.47
597 24 -22 -26 gg-tg 0.35
564 23 -1 -2 gg-gt 0.42
283 11 0 -1 gg-gg 0.65
184 7 -13 -10 gt-gt 0.33
Table SIII:
Cluster statistics from a cluster analysis of MD simulation w60. The average (Avg) and standard deviation (Std) of the and dihedral angles and the average total energy (Etot) are tabulated for all 19 clusters. The clusters are sorted by the conformation of the glucose rings. Clusters representing inverted glycosidic linkage conformations are listed separately at the bottom of the table. For each group, the total population and the group averages and standard deviations are added in bold font (Sum).
Figure 1: The conformational space of the glycosidic linkage dihedral angles and occupied during MD simulation w60 at 600K displayed in all four parts of the figures as hatched area. Overplotted in a thick closed line, the conformational space is indicated for those conformers that have A) 4C
14C1 B) 4C11C4 C) 1C44C1 D)1C4 1C
4 conformations of the reducing and the nonreducing glucose's,