First of all, I would like to thank my supervisor Uno Wennergren, for his great support during this year of my thesis work. He has been a great source of inspiration, encouragement and provoking advices.

I would like also thank the Department of Theoretical Biology at IFM of Linköping University, for providing me a perfect working environment with great brains around and all necessary equipments.

Last but not the least; I would like to thank Sara Gudmundson and Torbjörn Säterberg for their support and priceless friendships during this year.