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. Author manuscript; available in PMC: 2006 Jan 31.
Published in final edited form as: Nature. 2005 Nov 13;438(7067):460–465. doi: 10.1038/nature04268

Figure 4. RNAP backstepping and backtracking resolved at high resolution.

Figure 4

a, Backstepping observed under assisting loads of 18 pN at [NTP]eq. Molecules were occasionally found to move backward by one base pair (left and middle panels) or by two base pairs (right panel) before resuming elongation. b, Backtracking (>3 bp) under a hindering load of 9 pN. Molecules dwelled at specific preferred locations on the template before irreversibly backtracking (top) or recovering (bottom). Horizontal gridlines (dotted) are spaced at 3.4-Å intervals. (See Supplementary Information for a discussion.)