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(a) The DNA as a polymer between E and F and a specific binding site B (red). The transcription factors A3 in space (blue) in the same plane as the DNA and A1 on DNA (yellow) and two fixed roadblocks R1 (black). (b) The distance Lrb between the specific site B (red) and two fixed roadblocks (black) (top) and one fixed roadblock (bottom)
