2
$\begingroup$

I am using this article to calculate the radius of curvature of DNA. I know that

  • 150bp segment of DNA length wraps itself 1.7 times around a histone core.
  • There are 0.34nm/bp
  • DNA's persistence length l is 53 nm.

How can I use this data to calculate the radius of curvature of DNA?

According to the article, $l = \frac{B}{k_BT}$ ($B$ is bending modulus, $k_B$ is Boltzmann's constant, and $T$ is temperature). However, the only way the units cancel correctly is if $l = \frac{k_BT}{B}$. Which is the correct formula?

Assuming I know $T, k_B, l$, I can calculate $B$. Since DNA is a homogeneous isotropic rod, $B$ is equivalent to Young's modulus $E$. Is there a way I can use $E$ to calculate the radius of curvature? Or am I doing this completely wrong?

Improve this question
$\endgroup$
4
  • $\begingroup$ According to the article E= Bl/2R^2. Does that help? $\endgroup$
    – bob1
    Jun 7, 2022 at 21:30
  • $\begingroup$ Yes, but I am then confused how to get E/I. $\endgroup$
    – Monya Feldman
    Jun 8, 2022 at 1:14
  • $\begingroup$ I'm no mathematician by any stretch of the imagination, but it seems from the paper that E~kbT, and l~B/kbT thus by substitution l~B/E and therefore E~B/l for a given temperature and if R=l. I get units for l as N.mm^-2.J^-1, but it should be just distance (nm in DNA's case) correct? $\endgroup$
    – bob1
    Jun 8, 2022 at 2:08
  • 1
    $\begingroup$ I don't think DNA has a particular radius of curvature any more than it has a particular length. It will depend on the situation. In the case of DNA wrapped around a histone, the radius will be half the diameter of the histone + half the diameter of the DNA. $\endgroup$
    – timeskull
    Jun 8, 2022 at 16:32

0

Reset to default

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.