Background: This article describes the effects of nanosecond pulsed electric fields (nsPEFs) on the structure and enzyme activity of three types of proteins. Materials and Methods: Intense (up to 300 kV/cm) 5-ns-long electrical pulses were applied for 500 times at 3 Hz to solutions of lysozyme, albumin, and urease. We analyzed covalent bonds (peptide bonds and disulfide bonds) of lysozyme and albumin, and also the tertiary and quaternary structures of urease as well as urease activity. Results: The results indicated deformation of both the quaternary and tertiary structures of urease upon exposure to an electric field with an amplitude of 250 kV/cm or higher, whereas no structural changes were observed in lysozyme or albumin, even at 300 kV/cm. The enzyme activity of urease also decreased at field strengths of 250 kV/cm or higher. Conclusion: Our experiments demonstrated that intense nsPEFs physically affected the conformation and function of some types of proteins. Such intense electric fields often occur in cell membranes when exposed to a moderate pulsed electric field.

10This paper describes the effects of nanosecond pulsed electric fields (nsPEFs) on the structure and 11 enzyme activity of three kinds of proteins. Intense (up to 300 kV/cm), 5-ns-long electrical pulses were 12 applied to solutions of lysozyme (14 kDa, monomer), albumin (67 kDa, monomer), and urease (480 13 kDa, hexamer). We analyzed the tertiary and quaternary structures of these proteins as well as their 14 enzyme activity. The results indicated the deformation of both the quaternary and tertiary 15 structures of urease upon exposure to an electric field of 250 kV/cm or more, whereas no structural 16 changes were observed in lysozyme or albumin, even at 300 kV/cm. The enzyme activity of urease 17 also decreased at field strengths of 250 kV/cm or more. Our experiments demonstrated that intense 18 nsPEFs physically affect the conformation and function of some kinds of proteins. Such intense 19 electric fields often occur on cell membranes when these are exposed to a moderate pulsed electric 20 field. 21