Investigating the impacts of DNA binding mode and sequence on thermodynamic quantities and water exchange values for two small molecule drugs.
Doxorubicin and nogalamycin are antitumor antibiotics that interact with DNA via intercalation and threading mechanisms, respectively. Because the importance of water, particularly its impact on entropy changes, has been established in other biological processes, we investigated the role of water in these two drug-DNA binding events. We used the osmotic stress method to calculate the number of water molecules exchanged (Δnwater), and isothermal titration calorimetry to measure Kbinding, ΔH, and ΔS for two synthetic DNAs, poly(dA·dT) and poly(dG·dC), and calf thymus DNA (CT DNA). For nogalamycin, Δnwater<0 for CT DNA and poly(dG·dC). For doxorubicin, Δnwater>0 for CT DNA and Δnwater<0 for poly(dG·dC). For poly(dA·dT), Δnwater~0 with both drugs. Net enthalpy changes were always negative, but net entropy changes depended on the drug. The effect of water exchange on the overall sign of entropy change appears to be smaller than other contributions.
Department of Chemistry, St. Lawrence University, 23 Romoda Drive, Canton, NY, USA; Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA. Electronic address: rkenn10@gmail.com.
Rachael M
RM
Kenney
Department of Chemistry, St. Lawrence University, 23 Romoda Drive, Canton, NY, USA; Department of Chemistry, University of Wisconsin, Madison, WI, USA. Electronic address: kbuxton@chem.wisc.edu.
Katherine E
KE
Buxton
Department of Chemistry, St. Lawrence University, 23 Romoda Drive, Canton, NY, USA. Electronic address: sglazier@stlawu.edu.
Samantha
S
Glazier
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002417:Cattle; D004247:DNA / Q000737:chemistry*; D004317:Doxorubicin / Q000737:chemistry*; D019277:Entropy; D009621:Nogalamycin / Q000737:chemistry*; D011067:Poly dA-dT / Q000737:chemistry; D011089:Polydeoxyribonucleotides / Q000737:chemistry; D013816:Thermodynamics; D014867:Water / Q000737:chemistry*
D011089:Polydeoxyribonucleotides; D014867:Water; D011067:Poly dA-dT; C019530:poly(dC-dG); D004317:Doxorubicin; D004247:DNA; C427203:calf thymus DNA; D009621:Nogalamycin
DNA; Doxorubicin; Hydration; ITC; Nogalamycin; Osmolyte