Watching the double helix form

Have you ever wished you would watch a movie of the double helix forming from two DNA single strands?  Well you can in this paper from a sociology major and college dropout, now a professor in Korea.  I am not making this up.

It’s all in Proc. Natl. Acad. Sci. vol. 117 pp. 1283 – 1292 ’20 probably behind a paywall, so hopefully you or your institution has a subscription.  Here’s a link — https://www.pnas.org/content/117/3/1283

Here’s how they did it.  They designed and synthesized DNA sequences 90 nucleotides long — either random, pentablock (whose definition I can’t find in the paper, or palindromic so a double helix could be formed.  Then they used something called liquid cell transmission electron microscopy, which fires electrons through a sample to form an image on film.  The sample is prepared in phosphate buffered saline in D2O (not H2O — this to limit bubbles formed by the energy of the electrons.  The sample is then placed between two atomically thin graphene multilayers, and imaged.

Each image didn’t use a lot of electrons and took some 300 milliseconds to acquire.  Transient absorption of the DNA to the graphene slowed their motion so they could be ‘seen’ in the imaging frames.

There are several movies in the paper which must be seen to be believed.  For some reason they can’t be seen in the PDF version, so just go to the article and view them.

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