Due to some distribution in the length, the duplexes obtained after hybridization are characterized with the presence of dangling ends composed of single strands. This state manifests itself in the melting curve [42], the shape of which acquires the slight slope in the low-temperature part and the broadening of
helix → coil transition in comparison with the initial duplex (18°C vs 8°C). Note that there is a difference in absolute values of hypochromic (Figure 2, curve 1) and hyperchromic (Figure 3, curve 1) coefficients. This difference disappears after taking into account the contribution of the hyperchromic effect of the ordered poly(rC) in the total hyperchromic coefficient at heating [43]. The similar contribution of poly(rI) in this melting curve is insignificant because this CFTRinh-172 nmr polymer is characterized with base disordering even at room temperature [23]. Hybridization of free poly(rI) with poly(rC) adsorbed to SWNT Hybridization kinetics of poly(rI) with poly(rC) adsorbed to the nanotube surface (poly(rC)NT) is different from that observed for selleck kinase inhibitor free polymers by a smaller value of the hypochromic coefficient, although find more shapes
of time dependences are similar (Figure 2, curve 2). In the fast stage of kinetics, about 40% of base pairs are formed after the first 80 s. Comparing the times taken for the formation of 50% of base pairs (t 1/2), we found a slowdown of hybridization kinetics of polymers on the nanotube of 80 times (t 1/2 ≈ 40 min), compared to the hybridization kinetics of free Anacetrapib polymers in solution for which t 1/2 was 30 s. Then, the kinetic of this process becomes linear with time, so that for approximately 4.5 h, the number of base pairs increases by 10% and runs up to 60% that corresponds to the hypochromic coefficient of 0.25. It should be noted that by this time, the hybridization process slows down, and for the following 19 h, the increase in the number of base pairs was no more than 22%. For 24 h, the total part of hybridized pairs was
about 82% that resulted from a value of the hypochromic coefficient equal to 0.35. Similar time dependence was observed for kinetics of dsDNA formed with 20-bases linear DNAs on SWNT [18]. Slowing down of kinetics in the final stage is due to the steric constraints that inhibit the formation of hydrogen-bonded cytosine-hypoxanthine pairs and block zippering process [44, 45]. Similar behavior of hybridization kinetics of two complementary DNAs (or RNAs) on the nanotube was observed earlier [6, 17]. The melting curve of poly(rI) · рoly(rC)NT after 24-h hybridization is shown in Figure 3 (curve 3). It should be noted that upon poly(rC) adsorption onto the nanotube, the self-stacking of bases is lost [23], and therefore, the contribution of poly(rC) hyperchromicity is practically absent, and curve 3 represents mainly destruction of poly(rI) · рoly(rC)NT double-stranded parts.