Figure 6.
Chemical shifts of the low field methyl protons of the TG4T monomer versus the TG4T free monomer concentration. The shifts and the monomer concentrations were measured on spectra collected at different times during the formation of (TG4T)4 in oligonucleotide solutions containing 4 × 10−5 (open squares), 1.3 × 10−4 (black circles), 2 × 10−4 (open circles), 5 × 10−4 (black squares), 7 × 10−4 (black triangles) and 10−3 M (open triangles). The chemical shift variation versus the monomer concentration suggests fast exchange between the monomer and an intermediate species, presumably (TG4T)2. The monomer TCH3 frequency is estimated to 1.831 p.p.m. The computed solid lines were obtained by assuming dimer TCH3 frequencies of 1.5 and 1.6 p.p.m. and dimer dissociation constants of 6 × 10−3 M and 2 × 10−3 M−1. Solution conditions: T = 0°C, [Na+] = 0.125 M.