## 3 Results and Discussion
### Evaluation of Ribosomes and Polysomes Adsorption on Functionalized Gold Surfaces
#### 3.2.1 Ribosome Adsorption  
Prepurified ribosomes adsorbed on the bare gold surface appeared as evenly distributed ellipsoidal features, similar in dimension, mainly isolated, although a few cluster of 2-4 objects could be observed. Some smaller particles could also be recognized (Figure S4, panel A). To extract geometrical characteristic parameters, a grain-analysis algorithm was applied using the Gwyddion software, on several sample areas. The distributions calculated from the AFM images were fitted with Gaussian curves (Figure S5) and used to obtain the center and the width of the distribution peaks (see Table 2). The values of height and of minimum and maximum size obtained for ribosomes adsorbed on bare gold are smaller than those found by [PERSON] et al. [25]) for the 80S fraction deposited in standard conditions (i.e., (height: \(6.0\pm 1.0\) and \(9.1\pm 1.2\)) nm, (width: \(34.1\pm 3.9\)) nm, (length: \(42.2\pm 6.7\)) nm, respectively. These results indicate that some mild degradation induced by the interaction with the surface may occur for ribosomes deposited on bare gold.  
A variable extent of such degradation was found when depositing the same ribosomal fraction on the gold functionalized surfaces. A minimal degradation was observed for MCOOH surfaces, where values very similar to those found by [PERSON] et al. [25] were obtained (see Table 2), while an almost complete degradation was found for M11 CH\({}_{3}\) surfaces. Typical AFM images are shown in Figures S4 and S6, as examples of the various surfaces. Ribosomes adsorbed on MCOOH and MNH\({}_{2}\) surfaces clearly showed a bimodal distribution. On MCOOH the two populations showed the best agreement among the tested conditions with previously published data (see [25]), while on MNH\({}_{2}\) surface the two populations show a larger deviation, height being lower and length greater than the reference data. Moreover, ribosomes adsorbed on the MOH surface presented a quite broad distributions (Figure S5), with a maximum frequency in the very low population size. To be noted that ribosomes deposited on the surface M11 CH\({}_{3}\) aggregated in large bodies where single ribosomes could not be resolved, impeding their quantitative analyses (Figure S6). On this surface large, blurred aggregates, several nanometers high (see the height profile in Figure S6, panel B) were found, indicating an high degree of degradation of the ribosomal material due to the interaction with this hydrophobic surface.  
The density of ribosomes observed on the different surfaces was used as a numerical estimator of the ribosome affinity for the differently functionalized surfaces (Table 3). Beside bare gold surfaces, ribosomes showed a significant tendency to adhere to the MNH\({}_{2}\) treated surfaces. To be noted, the MNH\({}_{2}\) surface are endowed with a net positive charge distribution at physiological pH due to the presence of amino groups exposed on the surface.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & & & **(nm, Center/Width)** & & & \\ \hline
**Surface** & **H1** & **H2** & **W1** & **W2** & **L1** & **L2** \\ \hline bare gold & 5.2/1.8 & - & 26.7/11.9 & - & 36.3/14.5 & - \\ \hline MCOOH & 4.6/1.0 & 8.6/1.1 & 14.0/4.4 & 34.2/4.5 & 22.1/6.3 & 42.2/5.6 \\ \hline MNH\({}_{2}\) & 3.8/0.5 & 7.2/1.5 & - & 40.5/11.5 & 50.5/6.2 & 71.7/9.0 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Height (H1, H2 ) and lateral size values (width—W1, W2, length—L1, L2) obtained from the Gaussian fits of the morphological value distributions of ribosomes deposited on bare and functionalized gold (center and width of Gaussian fits are shown). Data and fits are reported in Figure S5.