title: Competitive binding of anticancer drugs 5-fluorouracil and cyclophosphamide with serum albumin: Calorimetric insights.
abstract: BACKGROUND
  Isothermal titration calorimetry (ITC) has emerged as an excellent method to characterize drug-protein interactions. 5-Fluorouracil and cyclophosphamide have been used in combination for the treatment of breast carcinoma, though individually these drugs have also been useful in treating other types of cancer. A quantitative understanding of binding of these drugs with the transport protein under different conditions is essential for optimizing recognition by the protein and delivery at the target.
  
  
  METHODS
  The values of binding constant, enthalpy, and entropy of binding have been determined by using ITC. Fluorescence and circular dichroism spectroscopies have been used to obtain further support to calorimetric observations, monitor conformational changes in the protein and establishing stoichiometry of association.
  
  
  RESULTS
  The thermodynamic parameters have enabled a quantitative understanding of the affinity of 5-fluorouracil and cyclophosphamide with bovine serum albumin. The nature of binding has been unraveled based on effect of ionic strength, tetrabutyl-ammonium bromide, and sucrose which interfere in ionic, hydrophobic, and hydrogen bonding interactions. The binding site has been identified by using site marker warfarin in combination with 5-fluorouracil and cyclophosphamide. Further, the experiments have been done to establish whether both the drugs share the same binding site, and the effect of antibiotic drug carbenecillin and anti-inflammatory drug naproxen on their association.
  
  
  CONCLUSIONS
  Tuning optimum association of drugs with the transport vehicles for effective drug delivery requires identification of the nature of interacting groups in terms of energetics of interactions. Such studies employing ITC have direct significance in rational drug design.
authors: Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India.
authors: Anu A
authors: AA
authors: Thoppil
authors: UM-DAE Centre for Excellence in Basic Sciences, Santacruz (E), Mumbai 400 098, India.
authors: Sinjan
authors: S
authors: Choudhary
authors: Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India. Electronic address: nandk@chem.iitb.ac.in.
authors: Nand
authors: N
authors: Kishore
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000737:chemistry*; D001665:Binding Sites; D001667:Binding, Competitive; D002151:Calorimetry; D002228:Carbenicillin / Q000737:chemistry; D002417:Cattle; D002942:Circular Dichroism; D003520:Cyclophosphamide / Q000737:chemistry*; D005472:Fluorouracil / Q000737:chemistry*; D006860:Hydrogen Bonding; D057927:Hydrophobic and Hydrophilic Interactions; D007700:Kinetics; D009288:Naproxen / Q000737:chemistry; D009994:Osmolar Concentration; D011485:Protein Binding; D000644:Quaternary Ammonium Compounds / Q000737:chemistry; D012710:Serum Albumin, Bovine / Q000737:chemistry*; D013237:Stereoisomerism; D013395:Sucrose / Q000737:chemistry; D013816:Thermodynamics; D014859:Warfarin / Q000737:chemistry
chemical_list: D000970:Antineoplastic Agents; D000644:Quaternary Ammonium Compounds; D012710:Serum Albumin, Bovine; D013395:Sucrose; D009288:Naproxen; D014859:Warfarin; D003520:Cyclophosphamide; C009405:tetrabutylammonium; D002228:Carbenicillin; D005472:Fluorouracil
keywords: 5-Fluorouracil; Anticancer drugs; Binding thermodynamics; Bovine serum albumin; Cyclophosphamide; Isothermal titration calorimetry