Energetics of echinomycin binding to DNA.
Differential scanning calorimetry and UV thermal denaturation have been used to determine a complete thermodynamic profile for the bis-intercalative interaction of the peptide antibiotic echinomycin with DNA. The new calorimetric data are consistent with all previously published binding data, and afford the most rigorous and direct determination of the binding enthalpy possible. For the association of echinomycin with DNA, we found DeltaG degrees = -7.6 kcal mol(-1), DeltaH = +3.8 kcal mol(-1) and DeltaS = +38.9 cal mol(-1) K(-1) at 20 degrees C. The binding reaction is clearly entropically driven, a hallmark of a process that is predominantly stabilized by hydrophobic interactions, though a deeper analysis of the free energy contributions suggests that direct molecular recognition between echinomycin and DNA, mediated by hydrogen bonding and van der Waals contacts, also plays an important role in stabilizing the complex.
Department of Chemistry, Florida International University, 11200 SW 8th Street, Miami, FL 33199, USA.
Fenfei
F
Leng
Jonathan B
JB
Chaires
Michael J
MJ
Waring
D000818:Animals; D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000378:metabolism*; D002152:Calorimetry, Differential Scanning; D004247:DNA / Q000737:chemistry / Q000378:metabolism*; D004448:Echinomycin / Q000737:chemistry / Q000378:metabolism*; D019277:Entropy; D005399:Fishes; D006860:Hydrogen Bonding; D057927:Hydrophobic and Hydrophilic Interactions; D008297:Male; D008958:Models, Molecular; D009691:Nucleic Acid Denaturation / Q000528:radiation effects; D011485:Protein Binding; D011487:Protein Conformation / Q000528:radiation effects; D013094:Spermatozoa; D013696:Temperature; D013816:Thermodynamics; D014466:Ultraviolet Rays
D000900:Anti-Bacterial Agents; D004448:Echinomycin; D004247:DNA