The phosphorylation and de-phosphorylation reactions in the cell, through which the bio-energy is released from ATP hydrolysis in biological systems, are described in this paper. Firstly, the bio-energy is accepted by the vibrational amides in protein molecules in virtue of resonant mechanism of frequency or energy, and can transport along the protein molecules in soliton, which is formed by self-trapping of vibrational quantum (or exciton), by means of dipole–dipole interaction among the neighboring peptide groups (or amino acids). Theory and properties of bio-energy transport were proposed and described by many researchers. We here reviewed mainly the theories and features of Davydov's and Pang's models. However these theoretical models including Davydov's and Pang's model were all established based on a periodic and uniform proteins, which are different from practically biological proteins molecules. Therefore, it is necessary to inspect and verify the validity of the theory of bio-energy transport in real biological protein molecules. These problems were extensively studied by a lot of researchers using different methods in past thirty years, a considerable number of research results were obtained. I review here the situation and progresses of study on this problem, in which we reviewed the correctness of the theory of bio-energy transport including Davydov's and Pang's model and its investigated progresses under influences of structural non-uniformity and disorder, side groups and imported impurities of protein chains as well as the thermal perturbation and damping of medium arising from the biological temperature of the systems. The structural non-uniformity arises from the disorder distribution of sequence of masses of amino acid residues, side groups and imported impurities, which results in the changes and fluctuations of the spring constant, dipole–dipole interaction, exciton–phonon coupling constant, diagonal disorder or ground state energy and chain–chain interaction of the molecular channels in the dynamic equations in different models. The influences of structural non-uniformity, side groups and imported impurities as well as the thermal perturbation and damping of medium on the bio-energy transport in the proteins with single chain and three chains were studied by different numerical simulation techniques and methods including the average Hamiltonian way of thermal perturbation, fourth-order Runge–Kutta method, Monte Carlo method, quantum perturbed way and thermodynamic and statistical method, and so on. In this review, the numerical simulation results of bio-energy transport in uniform protein molecules, the influence of structural non-uniformity on the bio-energy transport, the effects of system temperature on the bio-energy transport and the simultaneous effects of structural non-uniformity, damping and thermal perturbation of proteins on the bio-energy transport in single chains and α-helical molecules were included and studied, respectively. The results obtained from these studies and reviews suggest that Davydov's soliton is unstable, but Pang's soliton is stable at physiologic temperature 300 K under influences of structural non-uniformity and disorder, side groups, imported impurities and damping of medium. Thus we can conclude that the soliton in Pang's model is exactly a carrier of the bio-energy transport and Pang's theory is appropriate to α-helical protein molecules. Finally we provided a few of experimental evidences for real existence of the soliton and validity of the theory of bio-energy transport in proteins and stated further the applications of the theory in living systems.
The scattering of light in protein solutions. I—Gelatin solutions and gels
