80 DNA 70 Overstretching region To determine the mechanical properties of DNA we attach a bead...

  

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80 DNA 70 Overstretching region To determine the mechanical properties of DNA we attach a bead to each end of a long DNA strand and stretch it. The graph shows the extension (in nm) of the strand as a function of the force (in pN) applied. At strengths below 3 pN, DNA behaves like a spring. A. Use the zoomed-in graph to estimate the "spring constant" of the DNA in the region from 0.28 to 0.32 nm. Force (PN) 60 50 40 30 B. Using Us=kx estimate the work required to extend the DNA from 0.28 to 0.32 nm. 20 10 0 0.26 0.30 110 Losange 0.34 0.38 0.42 0.46 0.50 0.54 Extension (nm per base pair) 0 TT 0.26 0.30 C. Repeat your previous calculation using the fact that the area under the Force vs position graph is the amount of work done to achieve the extension. You may approximate the shape by a triangle. D. Repeat part (C) for the extension of DNA from 0.42 to 0.46 nm. You may approximate the shaded area by a rectangle. 80 DNA 70 Overstretching region To determine the mechanical properties of DNA we attach a bead to each end of a long DNA strand and stretch it. The graph shows the extension (in nm) of the strand as a function of the force (in pN) applied. At strengths below 3 pN, DNA behaves like a spring. A. Use the zoomed-in graph to estimate the "spring constant" of the DNA in the region from 0.28 to 0.32 nm. Force (PN) 60 50 40 30 B. Using Us=kx estimate the work required to extend the DNA from 0.28 to 0.32 nm. 20 10 0 0.26 0.30 110 Losange 0.34 0.38 0.42 0.46 0.50 0.54 Extension (nm per base pair) 0 TT 0.26 0.30 C. Repeat your previous calculation using the fact that the area under the Force vs position graph is the amount of work done to achieve the extension. You may approximate the shape by a triangle. D. Repeat part (C) for the extension of DNA from 0.42 to 0.46 nm. You may approximate the shaded area by a rectangle.