# Effects of Pulsed Electric Fields on Yeast with Prions and the Structure of Amyloid Fibrils
## 3 Results  
Yeast cells were grown until the culture reached the stationary phase (Figure 2). The results showed that yeast prions significantly affected cell growth dynamics. Psi\(-\) in the SC medium reached the stationary phase after 48 h of growth. The growth dynamics of the [PSI+] cells, with a weak variant of the prion, exhibited the same growth dynamics in the Lag and Log phase, but the Log phase was prolonged when compared to the [psi\(-\)] strain. The stationary phase reached 82 h of growth. A strong [PSI+] variant significantly altered the cell growth dynamics. The Lag phase was unusually extended, showing that prions affected cell adaptations in a new environment. The Log phase started after 48 h of growth; the stationary phase started after 78 h. _S. cerevisiae_ strain containing a strong [PSI+] variant reached about 3 times higher cell density in the SC medium as compared to the weak prion and 6 times higher as compared to the [psi\(-\)] strain.  
The PEF treatment results are presented in Figure 3. The presence of the prions in the yeast cells significantly increased cell resistance to PEF treatment. Further, [psi\(-\)  
Figure 2: Growth dynamics of _S. cerevisiae_ cells in the SC medium. The orange line represents the growth of _S. cerevisiae_ with a strong [PSI+] variant; the green line represents the growth of _S. cerevisiae_ with a weak [PSI+] variant; the blue line represents growth of _S. cerevisiae_ without [PSI+]. Data presented as average \(\pm\)SE.  
cells viability decreased to 40.55 \(\pm\) 9.59% after applying 2 kV/cm 1000 us pulse duration, 5 pulses; therefore, cells with strong and weak prions were not affected. Significant differences in cell viability between different prion variants were observed after applying 6 kV/cm PEF. Weak prions were less resistant to PEF as compared to strong ones. Even after 22 kV/cm PEF treatment, 9.58 \(\pm\) 0.69% viability of strong [PSI+] variant was observed.  
The stress-induced prionization analyses revealed that our conditions of PEF treatment did not induce the appearance of the [PSI+] prions in yeast cells or switches from the weak to the strong variant of the prion.  
Different electric field strength and pulse duration were tested in the disintegration of the Sup35 NM amyloids (Figure 4). Figure 4A presents the control sample of the purified Sup35 NM fibrils. The concentration of 10 uM was suitable for atomic force analysis. Fibrils were visible and single amyloid are present in the field without interfering with each other.  
The length of the PEF non-treated fibrils varies from 170 nm to 8.1 um. Small white dots on the sample were the oligomers of Sup35 NM. The diameter of the fibrils was \(8.3\pm 2.19\) nm. Application of 10 kV/cm, 50 us pulse duration, and 10 pulses resulted in a length reduction in the amyloid fibrils when compared to the control (Figure 4B). The longest fibril found in the samples was 1.45 um long and this was around four times less than the amyloid from the control samples. An increase in PEF pulse duration to 1000 us resulted in higher fibril disintegration (Figure 4C). Fewer long amyloids and more oligomers were observed in the sample. Finally, 20 kV/cm, 1000 us pulse duration, and 10 pulses were responsible for the full disintegration of the fibrils to oligomers (Figure 4D). It is important to point out that the diameter of the Sup35 fibrils increased according to the applied PEF duration. The diameter of 50 us treated fibrils was 11.1 \(\pm\) 3 nm and 1000 us 20.4 \(\pm\) 5 nm.  
Figure 3: Viability (%) of the _S. cerevisiae_ cells after exposure to a pulsed electric field (PEF) with different strength of electric field (kV/cm), 1 ms pulse duration, 5 pulses. Orange bars represent the viability of _S. cerevisiae_ with a strong [PSI+] variant; green bars represent the viability of _S. cerevisiae_ with a weak [PSI+] variant; blue bars represent the viability of _S. cerevisiae_ without [PSI+]. Data presented as average \(\pm\)SE.