A topology is a directed graph, which reflects the linkage of residues to each other, ignoring the nature of residues themselves. At this stage, all residues are considered as identical objects (nodes), which can have one or no outgoing linkages and any number of ingoing linkages.
Every node is depicted by a black dot in the icons. The order numbers are used to address nodes in string representation of topologies (together with "0", which means absence of a node). Arrows depict linkages connecting a donor (substituting residue, "child" in a graph) and an acceptor (substituted residue, "parent" in a graph). Square brackets indicate that a topology relates to the repeating unit of a regular polymer, while oligomeric topologies do not have square brackets. The inter-repeat linkage is assumed; it does not have an arrow in the icon.
To update the list of topologies for a given number of residues, edit this number in the first line of the form and press Show. By checking Widespread you can display only widespread topologies used in simple modes of structure generation. This omits topologies with branched nodes having more than two substituents, and polymers having equal or more residues in side chains than in a backbone.
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