Modelling the deoxyribonucleic acid (DNA) dynamics and understanding the action of all the various factors involved remain the major challenge in Nonlinear Physics, biology and even in chemistry. This vivid interest arises of course not only from the biological relevance of DNA but also from its physical properties which can now be probed through single-molecule micromanipulation experiments. It is no more to be demonstrated that nonlinear distortions could play a major role in DNA functions, where nonlinear interactions can give rise to very stable excitations, called solitons, capable of travelling without changing their shape. Different aspects of these excitations are discussed in this book and their role in the key processes of respiration, replication and transcription of DNA are discussed, the specific aim being to unmask and understand the responsibility of enzymes in energy transport and storage for the fulfillment of specific biological purposes.