Mechanical Unfolding and Amorphous Aggregation of Protein in a Very Low DC Field

Abstract

A common theme for the effect of electric field on the structure and conformation of proteins is lacking due to a myriad of conflicting reports emerging from different protein systems subjected to different frequencies and strengths of the field (0.8 −108 V cm–1), which may be pulsed for a few nano- to microseconds or applied continuously up to several hours. It is however necessary to find a common theme because of the increasing use of electric field not only to understand Stark-like electro-optic effects in large molecules but also in food processing technology, and perhaps in the disruption of amyloid bodies in Alzheimer’s condition. This study finds an optimized condition of 1.3 V cm–1 DC field, in which the electrophoretic mobility is ∼1.2 mm h–1, and systematically shows electrophoretic, electrochemical, and unfolding effects at different levels of cytochrome c structure within ∼90 min of turning the field on. Interestingly, the protein undergoes amorphous aggregation concomitant with a high degree of denaturation. In support of this suggestion, data for myoglobin and trypsin are also presented. Effort has been made to separate out the chemical and physical effects of the electric field.

Protein Crystallization in Very Weak DC Electric Field

“…The apparent difficulty here is to identify the structure of molecules in the mesoscopic phase A after the electric field is withdrawn, whether native (N), quasi-native (QN) or native-like conformations, or highly disordered (D) structure, or fibrillar cross-β structures; formation of all these types of structures in protein aggregates is possible. , They certainly do not have the N or QN-like structures because the tertiary structure is irreversibly lost as we see here (Figure ) and have also reported elsewhere very recently . The option of fibrillar structures can be eliminated right away because protein crystals will not nucleate from the irreversible cross-β forms, nor did we observe them in electron micrographs.…”