# How to determine whether the energy of a stem-loop fold is significant or not?

If I have a predicted RNA stem-loop of energy -0.30 kcal/mol, and another of -4.9 kcal/mol, how do I tell whether such a structure is a significantly stable structure or not? Our two competing hypotheses are that there is some structure with sufficient energetic stability to fold inside a cell, versus the one that there is not.

• A predicted stem loop of what? A nucleotide chain presumably, and most likely RNA but you need to tell us. Apr 23 '14 at 0:34
• Yes, it is an RNA. Allow me to update the original question. Many apologies for being unclear. Apr 23 '14 at 0:46
• probably the best way is to make it and see if the sequence forms a stem loop. there are lots of energy calculations based on 3d models and sequences if you'd like to know, but i'm not clear on what is best myself. Apr 23 '14 at 2:41
• I don't know what you mean by significant. More negative the value of folding energy more is the stability. For better predictions you can use the salt correction formulae. Apr 23 '14 at 3:21
• are you working on miRNA or tRNA or just other rnas?
– user1357
Apr 23 '14 at 6:37

You can convert the $\Delta G$ values into equilibrium constants $K$ using the formula

$$\Delta G = R T \ln K$$