Thermodynamics for proton dissociations from aqueous l-histidine at temperatures from 278.15 to 393.15K and at the pressure 0.35MPa: apparent molar volumes and apparent molar heat capacities of the protonated cationic, neutral zwitterionic, and deprotonated anionic forms

Thermodynamics of proton dissociations from aqueous l-methionine at temperatures from (278.15 to 393.15)K, molalities from (0.0125 to 1.0)mol·kg−1, and at the pressure 0.35MPa: Apparent molar heat capacities and apparent molar volumes of l-methionine, methioninium chloride, and sodium methioninate

“…The regression coefficients for equation (4) are given in table 8. Figure 2 shows our C p,/,obs (T, m) for HMet ± (aq) from table 5 and the regression surface, along with values from the literature [23][24][25].…”

“…Because there is no obvious reason to judge any of the literature results as either more or less reliable than any other, we have chosen to use the averages. Values of pK b and D r H m for reaction (8) were calculated from those for reaction (6) using values of pK w and D r H m;w from Patterson et al [38], giving pK b = (4.8 0 ± 0.2 1 ) and D r H m ¼ ð12:4 0 AE 0:4 1 Þ kJ Á mol À1 . We then fit by regression equation (4) to our derived C p,/ (i)(T, m) results for i = {H 2 Met + Cl À (aq)} and i = {Na + Met À (aq)}, again using the reciprocals of the uncertainties in C p,/,obs from tables 6 and 7 as weighting factors.…”

“…We have studied the most simple amino acid glycine [1], the aliphatic amino acids valine [2], L-2-aminobutanoic acid [2], proline [3], alanine [4], and isoleucine [5], as well as the heteroatomic threonine [5], serine [6], and histidine [7,8]. Our current work focuses on aqueous L-methionine.…”

Thermodynamics of proton dissociations from aqueous glycine at temperatures from 278.15 to 393.15 K, molalities from 0 to 1.0 mol·kg−1, and at the pressure 0.35 MPa: Apparent molar heat capacities and apparent molar volumes of glycine, glycinium chloride, and sodium glycinate

“…In equation (5), m i are the parameters of the regression, T* = (T/T ) with T = 1 K, m* = (m/m ) with m = 1 mol AE kg À1 , A V is the Debye-Hückel coefficient for volumes from Archer and Wang [17] as given in Sorenson et al [6], and where w = 0 for HGly ± (aq) and w = 1 for H 2 Gly + Cl À (aq) and for Na + Gly ± (aq). The regression parameters of equation (2) obtained from V /,obs in tables 1 to 3 are given in table 4.…”

“…A number of recent reports have dealt with thermodynamic properties of 2-amino acids at extremes of temperature or pressure, including references [1][2][3]. Recently, our laboratory has reported results for the apparent molar volumes V / and apparent molar heat capacities C p,/ of aqueous histidine [4,5], proline [6], valine [7], and L-2-aminobutanoic acid [7].…”