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Monotonicity, frustration, and ordered response: an analysis of the energy landscape of perturbed large-scale biological networks
 

Summary: Monotonicity, frustration, and ordered response: an analysis of
the energy landscape of perturbed large-scale biological networks
G. Iacono, C. Altafini
October 17, 2009
Abstract
For large-scale biological networks represented as signed graphs, the index of frustration
measures how far a network is from a monotone system, i.e., how incoherently the system re-
sponds to perturbations. In this paper we find that the frustration is systematically lower in
transcriptional networks than in signaling and metabolic networks. Interpreting this result
in terms of energetic cost of an interaction, an erroneous or contradictory transcriptional
action costs much more than a signaling/metabolic error, and therefore must be avoided
as much as possible. Averaging over all possible perturbations, however, we also find that
signaling/metabolic networks tend to undergo a phase transition to order in an energetic
regime lower than for transcriptional networks, meaning that, in spite of the higher frustra-
tion, they can achieve a globally ordered response to perturbations even for moderate values
of the strength of the interactions. Furthermore, an analysis of the energy landscape shows
that signaling and metabolic networks lack energetic barriers around their global optima, a
property also favouring global order. In conclusion, transcriptional and signaling/metabolic
networks appear to have systematic differences in both the index of frustration and the tran-
sition to global order. These differences are interpretable in terms of the different functions

  

Source: Altafini, Claudio - Functional Analysis Sector, Scuola Internazionale Superiore di Studi Avanzati (SISSA)

 

Collections: Engineering; Mathematics