Parameter:

ΔG°37 loop
(kcal/mol)

ΔH°loop
(kcal/mol)

Initiation n = 4 +1.1 ± 0.1 –7.2 ± 1.1
Initiation n = 5 +2.0 ± 0.1 –6.8 ± 1.8
Initiation n = 6 +2.0 ± 0.1 –1.3 ± 1.2
Asymmetry +0.6 ± 0.1 +3.2 ± 0.7
AU/GU closure +0.7 ± 0.1 +5.0 ± 0.7
1×(n–1) terminal mismatch 0 0
2×3 terminal mismatch:

5'RA
3'YG
0 0
5'YA
3'RG
–0.5 ± 0.2 –5.7 ± 3.8
5'RG
3'YA
–1.2 ± 0.1 –10.9 ± 2.7
5'YG
3'RA
–1.1 ± 0.1 –8.6 ± 1.9
G
G
–0.8 ± 0.2 –9.0 ± 4.6
U
U
–0.4 ± 0.1 –6.4 ± 2.5
other size terminal mismatch: 5'A
3'G
–0.8 ± 0.1 –3.4 ± 1.3
5G
3'A
–1.0 ± 0.1 –7.6 ± 1.0
G
G
–1.2 ± 0.1 +2.8 ± 2.4
U
U
–0.7 ± 0.1 –5.8 ± 1.1

Note: In the context of 2×3 internal loops, the orientation of the closing pair is considered, where R is a purine and Y is a pyrimidine.