Reaction systems models for the self-assembly of intermediate filaments S EPINOUD AZIMI AND CHARMI PANCHAL EUGEN CZEIZLER AND I ON P ETRE Abstract - Reaction systems are a recent addition to the spectrum of computational modeling frameworks. We construct in this paper several reaction systems models for the self-assembly of vimentin tetramers into intermediate filaments. We demonstrate that reaction systems are a versatile modeling framework, able to capture several aspects of the dynamics of the self-assembly of intermediate filaments using only simple, set-theoretical-based concepts. Key words and phrases : Reaction systems; modeling; intermediate filaments; self-assembly. 1 Introduction Reaction systems were introduced in [9] as a new modelling framework inspired by the functioning/bio-energetics of the living cell. It differs drastically from the traditional modelling frameworks (such as ODEs, stochastic processes, Boolean networks, state machines) in focusing on reactions and in having the environment as an integral part of the model. Reactions in reaction systems are enabled through promotion and inhibition, see [4]. Reaction systems are based on two main princi- ples. The first one, called the threshold principle makes reaction systems a qualita- tive framework by stating that if available, a resource (reactant) is available abun- dantly. In other words, reactions can not limit each other through a quantitative competition on resources. The second principle, called the no permanency princi- ple, states that a resource or reactant vanishes unless sustained by a reaction. That is to say, the next state of a reaction system is only obtained from the output of the reaction enabled in the previous state plus the contribution of the environment. Studies on reaction systems have been quite diverse, see for example [1, 3, 5, 10, 11, 15, 19, 22–25]. They can be categorized into two main streams. While the first direction is concerned with more theoretical aspects of reaction systems (e.g., [8,10,11,24,25]), the second direction has taken a more practical spin, mainly regarding reaction systems as a platform to do bio-modelling (e.g., [1, 3, 5]). In this paper we follow the second line of research and focus on the expres- sivity of reaction systems as a modelling framework. We consider a case-study on the self-assembly of intermediate filaments from vimentin tetramers. We start 1