Binding of volatile anesthetics to serum albumin: measurements of enthalpy and solvent contributions.
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Sawas AH, Pentyala SN, Rebecchi MJ
Binding of volatile anesthetics to serum albumin: measurements of enthalpy and solvent contributions.
Biochemistry. 2004 Oct 5;43(39):12675-85.
- PubMed ID
- 15449957 [ View in PubMed]
- Abstract
This study directly examines the enthalpic contributions to binding in aqueous solution of closely related anesthetic haloethers (desflurane, isoflurane, enflurane, and sevoflurane), a haloalkane (halothane), and an intravenous anesthetic (propofol) to bovine and human serum albumin (BSA and HSA) using isothermal titration calorimetry. Binding to serum albumin is exothermic, yielding enthalpies (DeltaH(obs)) of -3 to -6 kcal/mol for BSA with a rank order of apparent equilibrium association constants (K(a) values): desflurane > isoflurane approximately enflurane > halothane >or= sevoflurane, with the differences being largely ascribed to entropic contributions. Competition experiments indicate that volatile anesthetics, at low concentrations, share the same sites in albumin previously identified in crystallographic and photo-cross-linking studies. The magnitude of the observed DeltaH increased linearly with increased reaction temperature, reflecting negative changes in heat capacities (DeltaC(p)). These -DeltaC(p) values significantly exceed those calculated for burial of each anesthetic in a hydrophobic pocket. The enhanced stabilities of the albumin/anesthetic complexes and -DeltaC(p) are consistent with favorable solvent rearrangements that promote binding. This idea is supported by substitution of D(2)O for H(2)O that significantly reduces the favorable binding enthalpy observed for desflurane and isoflurane, with an opposing increase of DeltaS(obs). From these results, we infer that solvent restructuring, resulting from release of water weakly bound to anesthetic and anesthetic-binding sites, is a dominant and favorable contributor to the enthalpy and entropy of binding to proteins.
DrugBank Data that Cites this Article
- Drugs
- Drug Carriers
Drug Carrier Kind Organism Pharmacological Action Actions Desflurane Serum albumin Protein Humans UnknownBinderDetails Enflurane Serum albumin Protein Humans UnknownBinderDetails Halothane Serum albumin Protein Humans UnknownNot Available Details Isoflurane Serum albumin Protein Humans UnknownNot Available Details Propofol Serum albumin Protein Humans NoNot Available Details Sevoflurane Serum albumin Protein Humans UnknownBinderDetails