The July issue of Molecular Systems Biology, NPG’s open access journal published in partnership with EMBO (European Molecular Biology Organisation), is live. This month’s featured article is Systematic evaluation of objective functions for predicting intracellular fluxes in Escherichia coli, by Robert Schuetz, Lars Kuepfer & Uwe Sauer (Molecular Systems Biology 3, 119; 2007), with an accompanying News and Views article by Jens Nielsen (Molecular Systems Biology 3, 126; 2007). See the journal’s home page for more research papers, News and Views, Perspectives and Editorials, as well as links to systems biology papers published in the Nature journals.