## 3 Results and Discussion  
Before the UV absorption spectra can be presented for Syn solutions, under centrifugation conditions, it becomes necessary to analyze the UV absorption spectra obtained for the \(N_{\alpha}\)-acetyl-L-tyrosineamide (NAYA) parent compound for NAYA solutions, under the same centrifugation conditions. NAYA is a small molecule (MW = 222.24 gmol\({}^{-1}\)) when compared to the Syn protein (14,460 Da), but NAYA mimics the peptide bond of proteins and possesses a tyrosyl group similarly to the tyrosyl groups, found in the Syn protein molecular structure. In Figure 1A the UV absorption spectra for the NAYA compound is presented, revealing the aromatic and the peptide bond bands, when increasing the NAYA concentration in solution. It is clear from this figure that both tyrosine bands with maximums at 275 and at ca. 223 nm increased their absorbance when increasing the NAYA compound concentration. Notoriously, the bands corresponding to the peptide bond and to the tyrosyl group with maximum absorption at ca. 223 nm present a small shift of the maximum of their absorption towards longer wavelengths for the same solution conditions (Figure 1A). The shift towards longer wavelengths in UV spectra in aqueous solutions with variations of the solution concentration has been recently noticed [17]. The authors observed such a phenomenon and concluded that the shift towards longer wavelengths of the UV spectrum makes the concentration and absorbance deviate from Lambert-Beer's law [17]. It appeared that NAYA in aqueous solution presents irregularity of the electronic transition due to the absorption of UV light. Fortunately, the NAYA concentrations employed here were low and the corresponding concentration range used was small (6.71 \(\times\) 10\({}^{-5}\) M to 3.36 \(\times\) 10\({}^{-4}\) M), in comparison to the concentrations used in the above mentioned study [17]. This situationretrieves the small shift observed towards longer wavelengths (of few nanometers) for the absorption bands in the far UV absorption spectra (Figure 1A) and, therefore, minimizes the impact of the referred effects related to the variations of the NAYA concentration in the UV absorption spectra and in the corresponding quantitative analysis that was performed (Figure 1B,C). Moreover, in Figure 1B it can be seen that both the peptide bond and the tyrosine bands absorbance variations are linear but the variation of the peptide bond absorbance maximum is less pronounced in comparison to that of the tyrosl group absorbance maximum at ca. 223 nm. This can be due to some influence of the tyrosine absorption in the absorption of the peptide bond with increasing the NAYA concentration. It is worth noting that since at 205 nm the molar extinction coefficient of the tyrosl group (8500 M\({}^{-1}\) cm\({}^{-1}\)) [18] is much higher than that of the peptide bond (2780 M\({}^{-1}\) cm\({}^{-1}\)) [19], increased absorbance at ca. 223 nm should be expected for the tyrosl group where the maximum appears when compared to the absorbance at ca. 205 nm related to the peptide bond. In fact, it can be seen in Figure 1B that both the tyrosl group and the peptide bond showed roughly similar absorbance when the absorbance of the NAYA parent compound at 275 nm is ca. 0.4 (2.69 \(\times\) 10\({}^{-4}\) M). This can indeed be accounted for some influence of the tyrosl group absorption in the absorption of the peptide bond in the NAYA compound, as mentioned before. In Figure 1C, the determined areas of the absorption bands corresponding to the partially resolved peptide bond and the tyrosl group with maximum absorption at 275 nm are presented as a function of the NAYA concentration in solution.