## 3 Results and Discussion
The normalized UV absorption spectra are, in general, similar to those presented in Figure 3A with the exception of the appearance of a tail in Figure 3C when the membrane centrifugal filter with the 100 kDa cut-off is used. In Figure 3D the far UV absorption spectra for the same solutions depicted in Figure 3D are presented and similar conclusions can be drawn as referred to above for Figure 3B. That is, there is minor or no influence of the absorption of protein tyrosl groups in the absorption of the peptide bond in the Syn protein solution when the membrane centrifugal filter with the 30 kDa cut-off is used. Since it was previously referred to, the establishment of interactions between Syn protein tyrosl groups with protein peptide bonds formed can lead us to infer that minor or no formation of interactions with the Syn protein tyrosl groups with peptide bonds occur when Syn solutions are subjected to membrane centrifugal filters with the 30 kDa cut-off. In Figure 3E-G, the calculated difference spectra for Syn solutions using as reference the membrane centrifugal filter with the 200 nm cut-off are presented. In these figures, it can be seen that the amplitude of the calculated difference spectra with a maximum at ca. 291 nm reveals a decrease in the relation of the amplitudes from a more concentrated to a more diluted Syn solution when the membrane centrifugal filters cut-off is decreased. This result is intriguing and, for example, the calculated difference spectra _100 kDa \(-\) 200 nm_ shows a higher amplitude for a more diluted Syn solution when compared to what occurs for a more concentrated Syn solution (Figure 3E), which retrieves an increase in the intramolecular interactions between Syn peptide bonds and Syn tyrosl groups. This was expected in accordance with the rationalization made for the NAYA compound, in 10 mM tris-HCl (pH 7). Nevertheless, the calculated difference spectra _30 kDa \(-\) 200 nm_ shows, instead, lower amplitude for a more diluted Syn solution when compared to a more concentrated Syn solution (Figure 3G). Meaning, there is a decrease in the intramolecular interactions between Syn peptide bonds and Syn tyrosl groups. This was not to be expected in accordance with the above rationalization made for the NAYA compound, in 10 mM tris-HCl (pH 7). It appears that the phenomenon occurring in the Syn solutions is different from that predicted for NAYA solutions in 10 mM tris-HCl (pH 7), under stress induced conditions. It is worth mentioning that the above referred increase in the amplitude of the absorbance difference normalized occurred for longer wavelengths (less energetic) of the UV absorption difference spectra (ca. 320 nm to ca. 360 nm) (Figure 3G). This could mean that the \"less energetic\" phenomenon represents the display of long-range dynamics of the Syn tyrosl groups. Thus, the occurrence of long-range contacts for the Syn tyrosl groups is expected for a more concentrated protein solution and for the lowest membrane centrifugal filters used, under centrifugation conditions. The abovementioned phenomenon is one part of the scenario. The other part of the scenario is the \"more energetic\" phenomenon that could be the result of short-range dynamics of Syn tyrosl groups, i.e., for lower wavelengths of the UV absorption difference spectra (ca. 291 nm to ca. 320 nm) (Figure 3G). In fact, in Figure 3G there is an overlap of the UV absorption difference spectra in the latter wavelength region mentioned, i.e., for more concentrated and for more diluted Syn solutions. This could mean that the established short-range contacts of Syn tyrosl groups possess similar energetics, i.e., in a more concentrated and in a more diluted Syn solution, while there is significant disruption of intramolecular interactions between Syntyrosyl groups and Syn peptide bonds in a more concentrated Syn solution, in particular.