Table 3. Thermodynamic parameters for 19wt and its mutants in 5K buffer.

Name	Mutation	Potentially affecting	T m (°C)b	ΔTm (°C)	Hysteresis (°C)c
19wt	None	–	76.7 ± 0.6	–	6.4
M1	G5T	G5–C21 base pair	72.3 ± 0.4	−4.4	4.2
M2	G5T–A6T	G5–C21 and A6–T19 base pairs	78.5 ± 1.0	+1.8	6.1
M3	G5T–A6T–A22T	G5–C21 base pair and A6–T19–A22 triad	71.3 ± 0.4	−5.4	4.7
M4	C21A	G5–C21 base pair	76.1 ± 0.5	−0.6	7.3
M5	G5T–C21A	G5–C21 base pair: both nta	73.0 ± 0.4	−3.7	4.7
M6	G5A–C21A	G5–C21 base pair: both nt	69.6 ± 1.6	−7.1	6.7
M7	G5T–C21T	G5–C21 base pair: both nt	74.1 ± 0.9	−2.6	4.5
M8	C13A	π–π stacking between C13 and Quartet 1	76.4 ± 0.3	−0.3	6.2

^aNote the possibility of forming a new T–A Watson–Crick base pair.

^b T _m was measured from heating curves only.

^cHysteresis refers to the difference in T_m measured from heating and cooling profiles; the latter is systematically shifted towards lower temperatures by 4.2 to 7.3°C.