Figure 4.
Sedimentation velocity absorption profiles, recorded at 485 nm, of the ssDNA 20-mer, 5′-Pl-dA(pA)19, in the presence of the DnaB helicase in buffer T4, in the absence of nucleotide cofactors. The concentrations of the nucleic acid and the helicase were 3 × 10−6 M (oligomer) and 3 × 10−5 M (hexamer), respectively. The scans were collected at 30000 rpm. The short initial parts of the scans correspond to the buffer–air region above the sample meniscus. The arrows indicate the absorption of the total concentration of 5′-Fl-dA(pA)19 (T), the concentration of the 20-mer bound to the DnaB helicase (C), and the concentration of the free 20-mer (F). The horizontal lines indicate the locations of the plateaus corresponding to the zero line, free, 5′-Fl-dA(pA)19, concentration and the total, 5′-Fl-dA(pA)19, concentration (see the text for details).
