## 3 Results and Discussion
### Perming efficiency
To determine the isolated effect of each protein, the perme efficiency of the hair treated with the different proteins was compared with the perme efficiency of the hair treated with the respective ethanolic formulation (EtOH formulation) (Figure 4). Comparing the permeing results of the hair treated with proteins with the respective ethanolic formulations, higher perme efficiencies were obtained for the hair fibers treated with the proteins' in the ethanolic formulation prepared at pH 7. The higher contribution of the proteins at this pH could be explained by the low permeing efficiency obtained for the hair treated only with the ethanolic formulation at pH 7. Solutions with pH values close to 7 seem to influence the ratio between the number of salt bridges and hydrogen bonds, which are described to be involved in the shape of the hair fibers [33]. In this way, the low permeing efficiency observed for the control at pH 7 highlights the effect of the proteins in the shaping of the hair fibers. An exception was observed for BSA, where the lowest permeing efficiency (14.81%) was obtained for this pH value. This behavior could be explained by a more compact conformation of BSA at neutral pH [34]. As we move to other pH values, there is a relaxation in the BSA's structure, which may favor the interaction of this protein with hair fibers, increasing the permeing efficiency at pH 5 and pH 9 [34]. The goal of this work was to explore different proteins as valid alternatives to the chemical treatment usually applied to change the shape of hair. To analyze if the tested proteins show potential as hair permeing agents, the permeing efficiencies of the hairs treated with the proteins were compared with the permeing efficiency of the chemical method. Figure 4: Perming efficiency of the hair treated with the keratin, KP-UM, silk fibroin, BSA and KP-Cryst proteins prepared in phosphate buffer at pH 5, pH 7 or pH 9 compared to the respective “EtOH formulation” sample. Hair treated with a commercial formulation for permeing (“Chemical”), treated with the ethanolic formulation and phosphate buffers (“EtOH Formulation”), or without any treatment (“Control”) were used as controls for the proteins’ capacity to curl Asian hair. The values represent the mean \(\pm\) SD of two measurements. The data were analyzed by [PERSON]’s multiple comparison test: \(p\)-value \(\leq\) 0.05 (*), \(p\)-value \(\leq\) 0.01 (\(\bullet\)), and \(p\)-value \(\leq\) 0.0001 (\(\blacksquare\)) compared to the respective “EtOH formulation” data. In Table 2, the values for the perming efficiency ratios determined between the proteins treated hairs and the chemical treated hair are presented. The perming efficiency ratio provides a measure of a protein potential to be used as a performing agent when compared with the common chemical methods. Perming efficiency ratios close to one indicate that the protein has a perming capacity very similar to that of the chemical-based method. According to the results present in Table 2, we organized the protein formulations in ascending order considering their capacity to curl Asian hair:  
**pH 5** EtOH formulation \(<\) KP-Cryst \(<\) Silk fibroin \(<\) KP-UM \(<\) Keratin \(<\) BSA  
**pH 7** EtOH formulation \(<\) BSA \(<\) KP-UM \(<\) Silk fibroin \(<\) KP-Cryst \(<\) Keratin  
**pH 9** EtOH formulation \(<\) KP-Cryst \(<\) Silk fibroin \(<\) KP-UM \(<\) Keratin \(<\) BSA  
While BSA presented the highest potential to curl Asian hair at pH 5 and 9, but not at pH 7, the keratin showed good perming performances for all of the tested pH values, with perming efficiencies between 72% and 95% when compared with the chemical method. These results could be related to the fact that the tested keratin was extracted from human hair samples, thus presenting a high sequence identity with the hair, which could improve the keratin binding and perming performances [35]. Moreover, the high cysteine content of keratin could favor the formation of disulfide bonds with the high-sulfur hair matrix, improving the perming efficiency results [36].