Computational Methods in Systems Biology

Molecularbiologyhasuntilnowmainlyfocussedonindividualmolecules,on theirpropertiesasisolatedentitiesorascomplexesinverysimplemodelsystems. However,biologicalmoleculesinlivingsystemsparticipateinverycomplexn- works,includingregulatorynetworksforgeneexpression,intracellularmetabolic networksandbothintra-andintercellularcommunicationnetworks. Suchn- worksareinvolvedinthemaintenance(homeostasis)aswellasthedi?erentiation ofcellularsystemsofwhichwehaveaveryincompleteunderstanding. Nevertheless,theprogressinmolecularbiologyhasmadepossiblethedetailed descriptionofthecomponentsthatconstitutelivingsystems,notablygenesand proteins. Large-scalegenomesequencingmeansthatwecan(atleastinpr- ciple)delineateallmacromolecularcomponentsofagivencellularsystem,and microarrayexperimentsaswellaslarge-scaleproteomicswillsoongiveuslarge amountsofexperimentaldataongeneregulation,molecularinteractionsand cellularnetworks.^ Thechallengeofthe21stcenturywillbetounderstandhow theseindividualcomponentsintegrateintocomplexsystemsandthefunction andevolutionofthesesystems,thusscalingupfrommolecularbiologytos- temsbiology.