Dynamical features of deoxyribonucleic acid and configuration transition in the transcription process

Biological functions and genetic features of DNA, such as duplication, transcription and gene expression, are mainly determined by its structure, but depend also on the temperature and features of solution, such as salt concentration. We study the influence of temperature and salt concentration on the conformation changes and transcription of DNA by using a new dynamical model. This new model admits three degrees of freedom per base- pair: two displacement variables related to the vibrations of hydrogen atom in the hydrogen bonds and base (nucleotide), respectively, and an angular variable related to the rotation of base. The important role of motion of hydrogen atom in the hydrogen bonds is specially stressed in this model. This is helpful to reveal the mechanism of transcription of DNA. According to their properties of motion, we first give the Hamiltonian of the system, corresponding equations of motion and their soliton-solutions. The solitons are the excitation states formed by the displacements of hydrogen atoms and bases and the rotations of bases, arising from the energy absorbed by DNA, in the systems, respectively. By applying the transfer integral method we obtain the thermodynamic properties (e.g. free energy and entropy) of the thermal excitation state of DNA at the biological temperature in this model. According to the properties of these thermodynamic functions obtained we study the mechanism and processes of melting and transcription of DNA with the aid of the transforms of energy carried by the soliton in such a case. We further give the properties of the transcription of DNA with the help of the average value of the mean square of displacement of hydrogen atom, and the values of subcritical temperature and force of the phase transition are also found. Finally, we conclude that the transcription of DNA not only depends directly on the properties of its structure and of energy absorbed by it, but also is influenced by the temperature and salt concentration in the solution of DNA, which is consistent with experimental data. Therefore this new model not only can predict the transcription of DNA, but also can give the relationship among the conformation changes and the temperature and salt concentration. Finally we discuss in simple terms the influences of water or solution around DNA on its dynamics and further point out the defects and limitations of the new model of the dynamics of DNA and its direction of development.