The role of backward reactions in a stochastic model of catalytic reaction networks

University Ca’ Foscari Of Venice ,Alessandro Filisetti,Roberto Serra,Marco Villani,Alex Graudenzi,Chiara Damiani

doi:10.7551/978-0-262-31709-2-ch114

Abstract

We investigate the role of backward reactions in a stochastic model of catalytic reaction network, with specific regard to the influence on the emergence of autocatalytic sets (ACSs), which are supposed to be one of the pre-requisites in the transition between non-living to living matter. In particular, we analyse the impact that a variation in the kinetic rates of forward and backward reactions may have on the overall dynamics. Significant effects are indeed observed, provided that the intensity of backward reactions is sufficiently high. In spite of an invariant activity of the system in terms of production of new species, as backward reactions are intensified, the emergence of ACSs becomes more likely and an increase in their number, as well as in the proportion of species belonging to them, is observed. Furthermore, ACSs appear to be more robust to fluctuations than in the usual settings with no backward reaction. This outcome may rely not only on the higher average connectivity of the reaction graph, but also on the distinguishing property of backward reactions of recreating the substrates of the corresponding forward reactions.

Highlights

Models of catalytic reaction networks have been widely investigated in the last decades, with different goals and purposes, yet mostly in regard to the broad theme of the origin of life and with the design of artificial protocells (Carletti et al, 2008; Filisetti et al, 2010; Rasmussen et al, 2004; Serra et al, 2007; Szostak et al, 2001)
In order to fill the gap between theories and experiments and provide insights for further experimentation, in Filisetti et al (2011c) we introduced a novel model of catalytic reaction network, based on a fully stochastic framework and in which the system complexity can grow according to the dynamics, through the creation of new species and reactions
In our previous works we studied in depth the influence that variations in some of the key parameters of the system has on the overall dynamical behaviour and on the production of autocatalytic sets (ACSs)

Summary

Introduction

Models of catalytic reaction networks have been widely investigated in the last decades, with different goals and purposes, yet mostly in regard to the broad theme of the origin of life and with the design of artificial protocells (Carletti et al, 2008; Filisetti et al, 2010; Rasmussen et al, 2004; Serra et al, 2007; Szostak et al, 2001). Even if the dispute is far from being concluded (Cornish-Bowden and Cardenas, 2008; Stano and Luisi, 2010; Schrum et al, 2010; Budin and Szostak, 2010), one of the underlying key requirements in most of these theories is that the production of the molecular species involved in the transition relies on robust reaction pathways In this regard, some theories account for linear chemical pathways capable of producing the sufficient amount of species at energy-rich sites, e.g. hydrothermal vents (Ogasawara et al, 2000) or under plausible prebiotic conditions (Costanzo et al, 2009). The investigation of the generic properties of catalytic reaction networks, with particular respect to the sufficient conditions for the emergence of ACSs and the characterisation of their dynamical properties, is fundamental

Objectives

Findings

Conclusion