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. Author manuscript; available in PMC: 2014 Apr 30.

Published in final edited form as: Biochemistry. 2013 Apr 18;52(17):3000–3009. doi: 10.1021/bi4001408

Dependence of the interaction free energies on peptide length N. (A) – The free energy of interaction (in units of kT/bp) at the equilibrium spacing, D_eq, is calculated from the double exponential fits to the osmotic stress data and equation (7) for the arginine , ornithine , and lysine peptides. The much weaker attraction between DNA helices with lysine and ornithine peptides compared with arginine is apparent. (B) – The attractive and repulsive free energy components at 25 Å (in units of kT/bp) of the interaction are calculated from the double exponential fits to the osmotic stress force curves and equations (5) and (6). The repulsive, ΔG_R(25 Å)/kT, and attractive, ΔG_A(25 Å)/kT, free energies, respectively, are shown for the arginine ( , ◆), ornithine ( , ■) and lysine ( , ●) peptides.

Dependence of the interaction free energies on peptide length N. (A) – The free energy of interaction (in units of kT/bp) at the equilibrium spacing, D_eq, is calculated from the double exponential fits to the osmotic stress data and equation (7) for the arginine , ornithine , and lysine peptides. The much weaker attraction between DNA helices with lysine and ornithine peptides compared with arginine is apparent. (B) – The attractive and repulsive free energy components at 25 Å (in units of kT/bp) of the interaction are calculated from the double exponential fits to the osmotic stress force curves and equations (5) and (6). The repulsive, ΔG_R(25 Å)/kT, and attractive, ΔG_A(25 Å)/kT, free energies, respectively, are shown for the arginine ( , ◆), ornithine ( , ■) and lysine ( , ●) peptides.