Theoretical Systems Biology Group, Centre for Bioinformatics, Imperial College London, South Kensington Campus, London SW7 2AZ, UK.|Theoretical Systems Biology Group, Centre for Bioinformatics, Imperial College London, South Kensington Campus, London SW7 2AZ, UK.|Theoretical Systems Biology Group, Centre for Bioinformatics, Imperial College London, South Kensington Campus, London SW7 2AZ, UK.|Theoretical Systems Biology Group, Centre for Bioinformatics, Imperial College London, South Kensington Campus, London SW7 2AZ, UK.|Theoretical Systems Biology Group, Centre for Bioinformatics, Imperial College London, South Kensington Campus, London SW7 2AZ, UK.