## 3 Results and Discussion
### ssDNA and GNPs
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & **R** & **F** & **FL** & **FL2** & **FL4** & **FT** & **FT2** & **FT4** \\ \hline Capacity, largest number of & \multirow{2}{*}{29 \(\pm\) 3} & \multirow{2}{*}{36 \(\pm\) 3} & \multirow{2}{*}{56 \(\pm\) 2} & \multirow{2}{*}{38 \(\pm\) 4} & \multirow{2}{*}{17 \(\pm\) 2} & \multirow{2}{*}{53 \(\pm\) 3} & \multirow{2}{*}{28 \(\pm\) 5} & \multirow{2}{*}{18 \(\pm\) 4} \\ DNA molecules per GNP & & & & & & & & \\ Capacity in terms of anchor & \multirow{2}{*}{-} & \multirow{2}{*}{336 \(\pm\) 12} & \multirow{2}{*}{384 \(\pm\) 48} & \multirow{2}{*}{408 \(\pm\) 48} & \multirow{2}{*}{318 \(\pm\) 18} & \multirow{2}{*}{336 \(\pm\) 60} & \multirow{2}{*}{432 \(\pm\) 96} \\ nucleotides per GNP & & & & & & & \\ K\({}_{\rm L}\), pM\({}^{-1}\) & & & & & & & \\ R\({}^{2}\) (\(p\) \(<\) 0.05) & & & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Parameters of adsorption of ssDNA on GNPs, as determined by the autoradiographic method. Figure 2: Adsorption capacity of GNPs for ssDNA. Curves of saturation of GNPs by radiolabeled ssDNA (**A**), and a typical plot for KL determination in GraphPad Prism (**B**). is why we compared these data with the adsorption of the control set of ssDNA: the FTn series. The homogenous composition of the single-stranded overhang in this series ensures that nitrogenous bases are less likely to take part in intra- or intermolecular NA-NA interactions while preserving the overall charge of the DNA molecules. One can see that, surprisingly, under these conditions, GNP affinity values of oligonucleotides of the same length are comparable between the two series (Figure 2A, Table 2). Only in the case of the dodecanucleotide extension (\(n=2\), FL2) is the oligonucleotide capable of 35% stronger binding to the surface of GNPs as compared to its control counterpart (FT2). Next, we assessed how the presence of the \"anchor\" hexanucleotide groups and their extension affect the outcome of loading of the surface of GNPs by the \"main\" segments (Figure 1) of FLn (or FTn) in the noncovalent ssDNA/GNP associate (compare the first and second rows in Table 2). Readers can see that the introduction of a single hexanucleotide L motif raises the capacity of GNPs for FL by more than 1.5-fold as compared to the initial oligonucleotide (F). Further extension proved to be fruitless: if we compare L1 with the L2 motif and then with the L4 motif under the standard conditions of assembly of nanoassociates (25 \({}^{\circ}\)C), there is no expected outcome. For instance, the introduction of the fourfold L motif (compare FL and FL4) causes a threefold decrease in the observed capacity of GNPs for ssDNA (from 56 \(\pm\) 2 to 17 \(\pm\) 2 molecules), while in terms of \"anchor\" nucleotides, there is an increase in capacity of only 1.2-fold. These data, overall, are consistent with experimental results [44] concerning the relation between the extension of an oligonucleotide by means of high-affinity motifs (via introduction of homoadenylate strands) and surface capacity of GNPs for the oligonucleotide. At the same time, it should be noted that our use of the L motif as a gold-binding \"anchor\" yields greater affinity of these types of extended oligonucleotides for GNPs as compared to oligo(dA)-containing analogs [23; 45; 46; 47]. In addition, the use of the L anchor is comparable--in terms of achieved efficiency of adsorption of DNA containing it on GNPs--with fluorescein-containing DNA. An increase in the efficiency of adsorption of fluorescently labeled DNAs on GNPs by severalfold as compared to native DNAs has been demonstrated by us elsewhere [14].