I'm seeing some people on my Twitter feed wondering about how they have to handle the mRNA vaccines and being surprised by some of the precautions that need to be taken around them, so I thought it could be fun to have a really nerdy thread explaining why.

As I have said before: RNA will degrade if you so much as look at it funny as an act of spite.

This is only minimally hyperbolic. Even though DNA is very stable (and in fact this makes DNA vaccines an attractive candidate), RNA is the opposite. Why?

the "D" in DNA stands for "deoxy-" which is a reference to the fact that the ribose sugar in its backbone is missing an OH group, specifically the 2'-OH. This 2'-OH group is present on the ribose sugar in RNA and it makes a world of difference.

*warning, organic chemistry next*

Both RNA and DNA are held together by phosphodiester bonds. These can undergo hydrolysis through in-line attack at the phosphorus electrophilic center via some suitable nucleophile (e.g. a hydroxide ion).

You may remember however that intramolecular reactions proceed more quickly than intermolecular ones, owing to the greater entropy required for intermolecular reactions. Hence in RNA, the 2'-OH has a tendency to react with the phosphate ester and auto-hydrolyze:

This leads to formation of 2',3'-cyclic nucleotides (note however these are not the same as the 3',5'-cyclic nucleotides that appear as second messengers e.g. cAMP, cGMP).

DNA cannot form these because it lacks a 2'-OH group.

Under alkaline conditions, the 2'-OH in RNAs can deprotonate to form a nucleophilic alkoxide that reacts as per the scheme above. DNA on the other hand cannot do this and is thus much more resistant to hydrolysis (but can still hydrolyze).

This reaction can also occur easily with heat, even small amounts of heat like what you get from room temperature.

That's why RNAs generally need ultracold storage. Under sane temperatures the RNA have a tendency towards this suicidal auto-hydrolysis.

If you're trying to produce an encoded peptide product, like the spike protein RBD, that's a problem because ribosomes can't figure out how to make the peptide from pieces of RNA.

So now you know: thaw gently. Do not shake vigorously. Treat with reverence. Only offer deferential glances at the RNA. Avoid direct eye contact- it's too much pressure (also it would be a waste of an RNA vaccine to put them in your eyes).

Also I put a fork in this thread bc some people wanted to know more about the intramolecular vs intermolecular reactions thing https://twitter.com/ENirenberg/status/1336371770279010306?s=20