(CRN Diagrams Example) We illustrate the flexibility of the diagrammatic notation with three CRN examples. Figure 1a shows the CRN with the single reaction \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$C + A \rightarrow C + B$$\end{document}C+A→C+B. The ball () indicates that C is a catalyst to the reaction \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$A \rightarrow B$$\end{document}A→B represented by the arrow (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\uparrow$$\end{document}↑). A species can act as both a reactant or catalyst in the same reaction, and similarly for a product. In Fig. 1b we depict the CRN with two reactions \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\{ A + A \rightarrow A + B, B + B \rightarrow B + A \}$$\end{document}{A+A→A+B,B+B→B+A}, in which both A and B catalyse themselves. Figure 1c depicts the CRN with reaction set \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\{ A + B \rightarrow B + B, C + B \rightarrow B + B \}$$\end{document}{A+B→B+B,C+B→B+B}, with species B catalysing multiple reactions, which is represented by a multiheaded edge with multiple s. This CRN transforms species A and C into species B.Fig. 1Diagrammatic notation for CRNs. a CRN with the single reaction \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$C + A \rightarrow C + B$$\end{document}C+A→C+B, in which species C catalyses the reaction \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$A \rightarrow B$$\end{document}A→B. b CRN with reactions \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\{ A + A \rightarrow A + B, B + B \rightarrow B + A \}$$\end{document}{A+A→A+B,B+B→B+A}, in which species A and B are both reactants, products and catalysts. c CRN with reactions \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\{ A + B \rightarrow B + B, C + B \rightarrow B + B \}$$\end{document}{A+B→B+B,C+B→B+B}, which demonstrates that B can be catalytic to multiple reactions