Thermochemistry of adenosine

Abstract

The thermochemistry of adenosine(cr) was studied by a variety of methods: the standard (pressure po= 0.1 MPa) molar enthalpy of combustion in oxygen at T= 298.15 K was measured by means of combustion calorimetry and was found to be ΔcHmo=−(5139.4 ± 3.3)kJ · mol−1; the standard molar heat capacity Cp, mowas determined by means of adiabatic calorimetry for the range 11 ⩽(T/K)⩽ 328 { Cp, mo= (290.10 ± 0.58)J · K−1· mol−1at T= 298.15 K}; and the saturation molality in water was measured by means of high-performance liquid chromatography and was found to be m(sat)= (1.849 ± 0.015) · 10−2mol · kg−1at T= 298.15 K. Derived quantities at T= 298.15 K for adenosine(cr) are the standard molar enthalpy of formation ΔfHmo=−(653.6 ± 3.6)kJ · mol−1, the third law standard molar entropy Smo= (289.57 ± 0.6)J · K−1· mol−1, and the standard molar Gibbs free energy of formation ΔfGmo=−(204.4 ± 3.6)kJ · mol−1. The function Φmo=Δ0TSmo−Δ0THmo/T for adenosine(cr) was tabulated for 5 ⩽(T/K)⩽ 320. A thermochemical cycle was used to calculate ΔfGmo=−(194.5 ± 3.6)kJ · mol−1, ΔfHmo=−(621.3 ± 3.6)kJ · mol−1, and Smo= (364.6 ± 0.7)J · K−1· mol−1for adenosine(aq) at T= 298.15 K. These values in turn were used to calculate standard molar formation properties at T= 298.15 K and ionic strength I= 0 for the adenosine 5 ′ -monophosphate (AMP), adenosine 5 ′ -diphosphate (ADP), and adenosine 5 ′ -triphosphate (ATP) series of aqueous species. Standard molar transformed formation properties for the aqueous biochemical reactants adenosine, AMP, ADP, and ATP have also been calculated at T= 298.15 K, pH= 7.0, pMg= 3.0, and I= 0.25 mol · kg−1.