Division of Computational Biology, The Department of Physics and Measurement Technology, Biology and Chemistry, Institute of Technology, Linköping University, S-581 83 Linköping, Sweden. hallen@ifm.liu.se|Division of Computational Biology, The Department of Physics and Measurement Technology, Biology and Chemistry, Institute of Technology, Linköping University, S-581 83 Linköping, Sweden. hallen@ifm.liu.se|Division of Computational Biology, The Department of Physics and Measurement Technology, Biology and Chemistry, Institute of Technology, Linköping University, S-581 83 Linköping, Sweden. hallen@ifm.liu.se