# Explanation request: why do U-U mismatches provide a bonus in most internal loops?

**URL:** https://forum.eternagame.org/t/explanation-request-why-do-u-u-mismatches-provide-a-bonus-in-most-internal-loops/1694
**Category:** Gameplay and Strategies
**Created:** [April 5, 2013, 2:21pm UTC](https://forum.eternagame.org/t/explanation-request-why-do-u-u-mismatches-provide-a-bonus-in-most-internal-loops/1694 "2013-04-05T14:21:00Z")
**Posts on this page:** 2
**Page:** 1

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### Author: ![hoglahoo](https://forum.eternagame.org/letter_avatar_proxy/v4/letter/h/9d8465/32.png) [@hoglahoo](https://forum.eternagame.org/u/hoglahoo)
#### Post date: [April 5, 2013, 2:21pm UTC](https://forum.eternagame.org/t/explanation-request-why-do-u-u-mismatches-provide-a-bonus-in-most-internal-loops/1694/1 "2013-04-05T14:21:00Z")

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Can anyone give a scientific explanation for why internal loops larger than 2-2 get U-U mismatch energy bonuses in the energy model we use, while almost every other mismatch does not yield a bonus?

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### Author: ![eternacac](https://forum.eternagame.org/letter_avatar_proxy/v4/letter/e/977dab/32.png) [@eternacac](https://forum.eternagame.org/u/eternacac)
#### Post date: [April 12, 2013, 1:05am UTC](https://forum.eternagame.org/t/explanation-request-why-do-u-u-mismatches-provide-a-bonus-in-most-internal-loops/1694/2 "2013-04-12T01:05:00Z")

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It is thought due to the extra hydrogen bonding U-U mismatches (and C-C mismatches) get. Eterna may only properly account for U-U.

Do a google search on U-U mismatch RNA stability or add internal loop to the search.