A Pseudo-catalytic Network Motif for Thiol-based Chemical Reaction Networks

The construction of chemical reaction networks (CRNs) is a formidable challenge because of their holistic and nonlinear nature. One approach to constructing CRNs involves combining fragments with distinctive properties, known as network motifs. Thiol chemistry is widely used in the construction of CRNs, with motifs available for positive and negative feedback loops. However, a simple catalytic motif has been lacking. Here, we developed a pseudo-catalytic motif using the reaction between cystamine and organic thiocyanates, which operates through a nucleophilic chain mechanism. Although similar to thiol autocatalytic systems, this reaction does not involve a doubling of the number of thiol species at any stage. The reaction is high-yielding and produces 2-amino-2-thiazoline. Its pseudo-catalytic nature manifests itself in the nearly linear relationship between the reaction rate and the amount of free thiols added at the beginning of the reaction. We demonstrated that this reaction can be regulated by external, time-dependent thiol signals and integrated into larger CRNs. We believe that this system will be a valuable addition to thiol chemistry, enabling the construction of CRNs with interesting functionalities.