IkappaB, NF-kappaB regulation model: simulation analysis of small number of molecules.

The regulation of IkappaB, NF-kappaB is of foremost interest in biology as the transcription factor NF-kappaB has multiple target genes. We have modeled a previously published model by Hoffmann et al. (2002) of IkappaB, NF-kappaB mathematically as discrete reaction systems. We have used stochastic algorithm to compare the results when there are large and small numbers of molecules available in a finite volume for each protein. Our results for small number of molecules show that with continuous presence of stimulation, nuclear NF-kappaB oscillates continuously in every individual cell rather than damping, which was observed in cell population results. This characteristic of the system is missed when averaged behavior is studied.