Volpert Graph of Chemical Reactions

In reaction network theory, the Volpert graph is a directed bipartite graph whose vertex sets are the chemical species and the reaction steps. There is an edge from a species to a reaction step if and only if the reactant complex of the reaction step contains the species, and there is an edge from a reaction step to a species if and only if the product complex of the reaction step contains the species. The Volpert graph turns out to be very important in theory and it corresponds to the definition of the graphs used by biochemists.