Figure 5.

Applications of single-molecule imaging in living cells. (A) Using diffusion standards, it was shown that RelA diffusion, when inactive, is slow, matching that of ribosomes. The figure is adapted from (48). (B) The spatial profile of RNA polymerase shows that actively transcribed genes tends to be present in the nucleoid periphery. The figure is adapted from (51). (C) Single-molecule imaging of transcription factor Ada shows that some cells do not contain any molecule of this factor (left), delaying DNA-damage responses. This heterogeneity is also reflected in the diffusion profile of the MutS protein (right), which recognizes DNA mismatches that form when Ada is not present to repair damaged DNA molecules. There are many more DNA-bound MutS molecules (reflecting the presence of mismatches) in cells with low Ada content compared to cells in which Ada is abundant. The figure is adapted from (55). (D) Electroporated DNA can provide measurements of single-molecule FRET and distances within living cells. The figure is reproduced with permission from (69). To see this figure in color, go online.