## 3 Results and Discussion
### Affinity-Rating Analysis  
The methodology of rating (affinity-rating analysis) the gold affinity in different DNA hexamers, allowing us to theoretically calculate the relative affinity of ssDNA for GNPs, has been proposed by us earlier [23]. By testing this method on the affinity of the present series of ssDNA for GNPs, we found that the statistically determined (theoretical) affinity  
Figure 3: The dependence of the capacity of GNPs for ssDNA R and F (**A**) or ssDNA of the L series (**B**) or of the T series (**C**) on the temperature of incubation of the ssDNA with GNPs. Modes of adsorption (on GNPs) of the ssDNA oligonucleotides that do not contain (**left**) or do contain (**right**) an “anchor” motif (**D**). of the studied FLn oligonucleotides forSNPs is well consistent with actually observed adsorption efficiency (Table 3). Readers can see that the rating of theoretical affinity forSNPs increases in the series F < FL < FL2 < FL4. At the same time, only FL has elevated capacity for GNPs (Figure 2) relative to the initial oligonucleotide, F, and the elongation of the L motif reduces the efficiency of binding of ssDNA to GNPs. The rating method makes it possible to explain the role of Ln and Tn \"anchors\" in the adsorption of ssDNA on GNPs. FL consists of two regions: F has a rating of 5.0 \(\times\) 10\({}^{-5}\), and the L motif (6 nucleotides long) 12.0 \(\times\) 10\({}^{-5}\), i.e., the affinity of these two segments of FL, when normalized to the number of nucleotides, differs by a factor of 2.4. As a consequence, the interaction of FL with GNPs is most likely mediated by the short 6-nt L motif. This interaction provides much greater occupancy of the surface of GNPs by FL molecules as compared to F. After the extension of the L motif to 12 and 24 nt, its theoretically expected affinity strengthens to 62.0 \(\times\) 10\({}^{-5}\) in FL2 and to 86.0 \(\times\) 10\({}^{-5}\) in FL4. Thus, with the increase in the length of the \"anchor,\" the affinity difference between the \"anchor\" and the \"main\" region of the molecule increases even more, by 12- and 17-fold, respectively. Now, the longer \"anchor\" is even more likely to be adsorbed on GNPs while occupying a larger proportion of the nanoparticle surface, thus leading to the observed decrease in capacity for FL2 and FL4. Moreover, the probability of formation of secondary structures in the elongated oligonucleotides is higher, which also results in lower capacity of GNPs for FL2 and FL4 as compared to FL. The hexathymidylate motif tends to lower the rating of the FTn containing it; that is, this motif in ssDNA no longer plays the role of an \"anchor\" that has paramount importance for the adsorption of ssDNA on GNPs. Its introduction into DNA (and extension) does not result in preferential adsorption of the \"anchor\" part of DNA on GNPs. In other words, we see different levels of capacity for FT2 and FT4 with increasing temperature owing to the equivalent adsorption of different segments of their molecules, in contrast to FL2 and FL4 (Table 2). It can be said that the greater capacity of GNPs for FT compared to F is explained by (i) higher probability of a larger number of different binding modes with the extension of the molecule (Figure 3D), (ii) a slight increase in electrostatic repulsion after minimal elongation, and (iii) the absence of secondary structures. The electrostatic repulsion and its negative contribution to the capacity strengthen with further lengthening of the anchor (in FT2 and FT4). Therefore, during the interaction of the tested ssDNA with GNPs, different binding modes are realized:  
1. The presence of one short high-affinity sequence of the L motif significantly promotes binding precisely due to the direct contact of this motif with the surface of the metal nanoparticle;
2. The presence of the Tn motif, which does not have pronounced affinity for GNPs, causes predominant or equivalent interaction (with GNPs) of the other (\"main\") part of the oligonucleotide: in our case, F;
3.