Effects of static magnetic fields on the structure, polymerization, and bioelectric of tubulin assemblies

Abstract

Due to widespread exposure of human being to various sources of static magnetic fields (SMF), their effect on the spatial and temporal status of structure, arrangement, and polymerization of tubulin was studied at the molecular level. The intrinsic fluorescence intensity of tubulin was increased by SMF, indicating the repositioning of tryptophan and tyrosine residues. Circular Dichroism spectroscopy revealed variations in the ratios of alpha helix, beta, and random coil structures of tubulin as a result of exposure to SMF at 100, 200, and 300 mT. Transmission Electron microscopy of microtubules showed breaches and curvatures whose risk of occurrence increased as a function of field strength. Dynamic light scattering revealed an increase in the surface potential of tubulin aggregates exposed to SMF. The rate and extent of polymerization increased by 9.8 and 33.8%, at 100 and 300 mT, respectively, but decreased by 36.16% at 200 mT. The conductivity of polymerized tubulin increased in the presence of 100 and 300 mT SMF but remained the same as the control at 200 mT. The analysis of flexible amino acids along the sequence of tubulin revealed higher SMF susceptibility in the helical electron conduction pathway set through histidines rather than the vertical electron conduction pathway formed by tryptophan residues. The results reveal structural and functional effects of SMF on tubulin assemblies and microtubules that can be considered as a potential means to address the safety issues and for manipulation of bioelectrical characteristics of cytosol, intracellular trafficking and thus, the living status of cells, remotely.

Keywords:

• biophysics
• tubulin polymerization
• microtubule
• static magnetic field
• molecular flexibility

Acknowledgment

The authors would like to appreciate the financial support provided by the University of Tehran. The authors wish to thank Dr E.C. Thrower, University of Yale, USA, for his critical review and comments and also editing the English of the manuscript. The invaluable analysis of TEM experiments and resulted images that was kindly conducted by Professor L. Dini, University of Salento, Italy is highly appreciated. The authors also wish to thank constructive advises of Dr. Gharailou, Electron Microscopy Laboratory of Sharif University of Technology, Tehran, Iran toward the improvement of TEM-related experiments. The kind technical support of the head of Fargene Pouyesh Iranian Company, Eng H. Yazdi is much appreciated.