## 3 Results and Discussion
### Adsorption of dsDNA on GNPs  
Next, we compared the adsorption (on GNPs) of dsDNA carrying single-stranded overhangs (L series and T series 6, 12, and 24 nucleotides long) and of the initial blunt-ended duplex (Figure 1). It should be stressed that we assessed adsorption parameters of dsDNA by means of the balance of all the interacting ssDNA binding to the nanoparticle (Figure 4, Table 4). For this purpose, a radioactive 5\({}^{\prime}\)\({}^{32}\)P label was introduced into one or the other DNA strand. One can see that even at high concentrations of dsDNA (all duplexes were stable), we did not observe well-pronounced and equivalent efficiency levels of adsorption of both complementary DNA strands for any of the tested duplexes (Figure 4). A question arises: are such complementary ssDNA adsorbed on the surface of GNPs in the form of a duplex? The saturation curves of dsDNA F*-R and FLn*-R, which contain radiolabeled F strands, have a local maximum in the range of low concentrations of ssDNA (20-40 nM, Figure 4A-D), when the presence of a substantial amount of the ssDNA form in the reaction mixture should still be expected. Obviously, an increase in the concentration of the interacting strands to 100 nM should considerably reduce the probability of \"complementarity-mismatched\" interaction of individual DNA strands with GNPs. In this context, it is important to take into consideration that the strands released from dsDNA, which have a propensity for intra- and/or intermolecular interactions, can also lose the ability to independently bind to GNPs [15]. In the extreme case, an increase in the concentration of \begin{table}
\begin{tabular}{l l l l l l l} \hline \hline
**Initial dsDNA** & \multicolumn{6}{l}{**dsDNAs Containing Single-Stranded Overhangs Based On**} \\ \hline  & \multicolumn{2}{l}{**L Motif**} & \multicolumn{6}{l}{**T Motif**} \\ \hline F*–R & FL*–R & FL2*–R & FL4*–R & FT*–R & FT2*–R & FT4*–R \\
20 \(\pm\) 2 & 39 \(\pm\) 2 & 20 \(\pm\) 1 & 18 \(\pm\) 2 & 33 \(\pm\) 2 & 20 \(\pm\) 2 & 14 \(\pm\) 1 \\ F–R* & FL*–R* & FL2*–R* & FL4*–R* & FT–R* & FT2*–R* & FT4*–R* \\
16 \(\pm\) 1 & 13 \(\pm\) 1 & 13 \(\pm\) 2 & 6 \(\pm\) 1 & 13 \(\pm\) 1 & 16 \(\pm\) 2 & 11 \(\pm\) 2 \\ \hline \hline \end{tabular}  
* denotes radioactively labeled DNA.  
\end{table} 
Table 4: Capacity of GNPs for oligonucleotides as part of dsDNA, in molecules per GNP, at 25 \({}^{\circ}\)C.  
dsDNA and the consequent increase in Tm values (Table S2) determine the convergence of capacity values when we examine saturation curves of complementary ssDNA (with the exception of FL-R) (Figure 4A,C,D). It is for this reason that values of saturation capacity of the GNP surface for components F and FL2 relative to component R become significantly closer (Figure 4A,D), that is, under the conditions that are most conducive to the formation of dsDNA. Let us examine the same duplexes when the R strand is radiolabeled (Figure 4A-D). One can see that radiolabeled 20-mer R* in a stoichiometric mixture with any DNA of the L series adsorbs worse at most concentrations. Only \(\sim\)14 molecules of R* per GNP when mixed with F, FL, or FL2, and only six molecules of R* when mixed with long FL4, bind to a GNP, whereas 20 to almost 40 molecules of the L series of oligonucleotides were found cover the GNP. The use of the long L4 overhang (having high Au affinity, occupying greater specific area on the GNP surface, and creating the strongest electrostatic repulsion between adsorbed DNA strands within the associates with GNPs) further complicates the adsorption of R. As already mentioned, an important experimental finding here is the difference in saturation capacity of GNPs between FLn*-R and FLn-R* (at \(n=1\), 2, and 4). The capacity of GNPs for the labeled R* strand in mixtures with each FTr oligonucleotide was \(\sim\)13 molecules per GNP.