Heats of Combustion. VII. The Heats of Combustion of Some Amino Acids

Calculation of the standard molal thermodynamic properties of crystalline peptides

“…However, using the values of DH o f for cysteine in Table 5 and the average of the [CH 2 ] groups reported in Richard and Helgeson (1998), the aforementioned approximation yields an enthalpy of formation for methionine equal to À588.52 kJ mol À1 . This compares favorably to the value reported by Sabbah and Minadakis (1981), À577.48 kJ mol À1 , while DH o f for methionine derived from Tsuzuki et al (1958) is equal to À758.14 kJ mol À1 . This approximation supports using the DH o f for methionine reported by Sabbah and Minadakis (1981 Dick et al (2006).…”

“…where values for N AAi were taken from Helgeson et al (1998) except for V o for all amino acids, a and b for leucine, as noted above, and DH o f for methionine, which was based on an suspect enthalpy of combustion (Tsuzuki et al, 1958). A different experimental value for DH o f of crystalline Generic algorithm:…”

“…These values for crystalline methionine are listed in Table 5 along with revised values of DG o f , DH o f and S o for neutral, positive and negatively charged aqueous species of methionine, which were reported in Amend and Helgeson (1997a) and Dick et al (2006) and based on the erroneous value of DH o f ðcrÞ .These changes do not affect calculated values of DG o of solution for methionine, but do increase the values of DG o f for both crystalline and aqueous methionine. Though Sabbah and Minadakis (1981) do not discuss why the enthalpy of combustion they measured differs from that reported by Tsuzuki et al (1958), the values of DH o f derived from these measurements can be compared to an esti- Table 4 Linearized values of the heat capacity power function coefficients for the (ribose-deoxyribose) reaction and crystalline groups. Table 5 Summary of heat capacity power function coefficients and values of the standard molal thermodynamic properties at 25°C and 0.1 MPa for selected amino acids and peptides.…”

Standard molar enthalpies of formation of crystallinel-,d- anddl-valine

“…This phenomenon, and the limited accuracy of the calorimetric data, can make performing measurements of enthalpies of combustion on enantiomerically pure stereoisomers of the substances with one chiral centre unattractive, despite the biological importance of these thermochemical data, which are necessary if quantitative studies on the energetics of biochemical reactions are to be performed. The experimental measurements of the enthalpies of combustion for a large number of α-amino acids have been reported by different researchers, such as those obtained by Tsuzuki et al, (1,2) and Hutchens et al, (3) later by Kamaguchi et al, (4) and Sabbah et al, (5,6) and very recently by Yang et al (7) Some of these measurements introduced modifications to the experimental conditions of the combustion in order to obtain more reliable results for several compounds. On the continuation of our interest on the study of thermochemical properties for α-amino acid complexes, (8,9) we realized that the value for the enthalpy of formation of crystalline Dvaline was not available in the literature, although the standard molar enthalpy of formation for the crystalline L-valine isomer had been reported by Tsuzuki et al (1) and recalculated by Hutchens et al, (3) and Vasil'ev et al (10) reported one value for the standard molar enthalpy of formation of DL-valine.…”

Interplay of thermochemistry and Structural Chemistry, the journal (volume 17, 2006) and the discipline

“…In addition, the desirability of the comparative analysis of theoretical and experimental data in the case of coordination or protonation processes where a conformational distortion is shown. The enthalpy of formation of methionine [37,38] and its homopolymer [39] have been reported. The next paper in this issue by Hamamci, Yilmaz, and Kazak [40] reports the synthesis and spectral, thermal and structural characterization of a new coordination polymer of silver(I) with saccharinate and nicotinamide [Ag(sac) (nia)] n (sac = saccharinate; nia = nicotinamide = 3-pyridine carboxylic acid amide commonly known as vitamin B3).…”