title: Thermodynamics of the conversion of aqueous L-aspartic acid to fumaric acid and ammonia.
abstract: The thermodynamics of the conversion of aqueous L-aspartic acid to fumaric acid and ammonia have been investigated using both heat conduction microcalorimetry and high-pressure liquid chromatography. The reaction was carried out in aqueous phosphate buffer over the pH range 7.25-7.43, the temperature range 13-43 degrees C, and at ionic strengths varying from 0.066 to 0.366 mol kg(-1). The following values have been found for the conversion of aqueous L-aspartateH- to fumarate2- and NH4+ at 25 degrees C and at zero ionic strength: K = (1.48 +/- 0.10) x 10(-3), DeltaG degrees = 16.15 +/- 0.16 kJ mol(-1), DeltaH degrees = 24.5 +/- 1.0 kJ mol(-1), and DeltaC(p) degrees = -147 +/- 100 J mol(-1) K(-1). Calculations have also been performed which give values of the apparent equilibrium constant for the conversion of L-aspartic acid to fumaric acid and ammonia as a function of temperature, pH and ionic strength.
authors.affiliation: Chemical Thermodynamics Division, Center for Chemical Physics, National Bureau of Standards, Gaithersburg, MD 20899, USA.
authors.forename: R N
authors.initials: RN
authors.lastname: Goldberg
authors.forename: E
authors.initials: E
authors.lastname: Gajewski
authors.forename: D K
authors.initials: DK
authors.lastname: Steckler
authors.forename: Y B
authors.initials: YB
authors.lastname: Tewari