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. Author manuscript; available in PMC: 2011 Nov 2.
Published in final edited form as: Biochemistry. 2010 Nov 2;49(43):9152–9160. doi: 10.1021/bi100946g

Table 2.

Thermodynamic data for the c-Myc G-quadruplex loop-isomers formed by the extended and truncated DNA sequences, determined in the presence of 10 mM Li3PO4 (pH=7) containing different concentrations of K+. Samples were heated and cooled at a rate of 2°C /min.a

[K+] (mM) DNA Tm (°C) CTmb (°C) ΔH (kJ/mol) ΔS (kJ/molK) ΔG37 (kJ/mol) DNA Tm (°C) CTmb (°C) ΔH (kJ/mol) ΔS (kJ/molK) ΔG37 (kJ/mol)
0.5c 14/23 43 42 −129 −0.412 −1.86
2c 14/23 57 56 −173 −0.526 −9.92 T14/23T 57 57 −167 −0.508 −9.96
5 14/23 64 63 −181 −0.540 −14.03 T14/23T 65 65 −165 −0.491 −13.40
10 14/23 69 69 −185 −0.542 −17.57 T14/23T 69 69 −162 −0.475 −14.92
20 14/23 75 74 −212 −0.612 −22.59 T14/23T 73 72 −184 −0.535 −18.32
50 14/23 80 79 −192 −0.548 −22.93
0.5c 11/23 39 37 −120 −0.390 0.05
2c 11/23 52 52 −154 −0.476 −6.90 T11/23T 53 53 −156 −0.481 −7.18
5 11/23 60 60 −146 −0.439 −10.03 T11/23T 61 60 −166 −0.501 −11.60
10 11/23 64 63 −173 −0.516 −13.65 T11/23T 65 64 −159 −0.473 −12.37
20 11/23 72 71 −189 −0.550 −18.50 T11/23T 70 69 −189 −0.553 −17.45
50 11/23 75 75 −158 −0.454 −17.51
0.5c 14/20 34 34 −129 −0.421 1.41
2c 14/20 50 49 −154 −0.479 −5.70 T14/20T 48 48 −165 −0.515 −5.60
5 14/20 58 57 −159 −0.483 −9.70 T14/20T 57 56 −172 −0.523 −9.95
10 14/20 62 61 −159 −0.480 −11.10 T14/20T 61 61 −180 −0.540 −12.78
20 14/20 69 69 −178 −0.521 −16.49 T14/20T 66 65 −187 −0.553 −15.45
50 14/20 72 71 −158 −0.462 −15.39
0.5c 11/20 28 26 −108 −0.363 4.03
2c 11/20 47 46 −115 −0.362 −3.33 T11/20T 44 44 −150 −0.476 −3.00
5 11/20 53 52 −118 −0.364 −5.49 T11/20T 53 53 −164 −0.505 −7.76
10 11/20 57 56 −126 −0.386 −7.16 T11/20T 58 58 −165 −0.501 −10.15
20 11/20 65 64 −148 −0.442 −11.61 T11/20T 62 62 −173 −0.518 −12.81
50 11/20 67 66 −138 −0.408 −11.96
a

The samples were prepared at a DNA concentration of 10 μM. All experiments were performed at least twice and Tmvalues are accurate to within 1°C. ΔH, ΔS and ΔG values are given with an experimental error of ±5% determined on the basis of at least two independent experiments. Missing values at low concentrations of K+ correspond to quadruplexes for which the Tm values were too low to measure or for which too high hysteresis was observed between the melting and annealing profiles even by using the lowest rate of cooling and heating.

b

Melting temperatures (CTm) calculated from the equation (Tm = ΔH/ΔS).

c

Samples were heated and cooled at a rate of 0.5°C/min.