Nanomechanics instability (folding) and TeraHertz vibration in proteins: A piezonuclear interpretation of metabolic processes

It has recently been suggested that mechanical vibrations play a crucial role in controlling structural configuration changes (folding) which govern proteins biological functions. In particular, underdamped low-frequency (~10^11−10^12 Hz) collective vibrational modes in proteins have been proposed as being responsible for efficiently directing biochemical reactions and biological energy transport. In the case of the Na/K-ATPase, for example, the continuous exchange of sodium and potassium ions through the cell membrane, guided by protein folding, is accompanied by mechanical vibrations at frequencies around the TeraHertz range. In this contribution the results of experimental and numerical investigations on the sodium-potassium pump are presented. Broad-range Raman spectroscopy measurements were performed on both lyophilized and hydrated samples. The use of ultra low frequency (ULF) filters allowed to observe delocalized vibration at 0.81 THz (27 cm^−1), as well as other unassigned peaks in the range 0−500 cm^−1. These results find a correspondence with the ones provided by a numerical lattice model, where the linear normal modes were obtained by running a dynamic modal analysis. The theoretical resonant frequencies range from tens of GHz (vibrations of large protein portions) to tens of THz (vibrations of chemical groups/amino acids). In particular, the lower frequencies were found to be associated to vibrations of the protein ends, possibly facilitating ions migration through the cell membrane. A piezonuclear explanation of the ionic pump mechanism is eventually proposed. According to this hypothesis, the sodium and potassium ions would be subject to a continuous and recurrent transformation of one into the other, losing and regaining an oxygen atom at each passage through the cell membrane. In this process, protein folding should be regarded as a dynamic nano-buckling (with snap-through), where the abrupt configuration change is induced by electro-chemical forces acting on the oscillating system.