Modeling of transfer properties using revised HKF theory: thermodynamics of transfer of an amino acid and small peptides from water to urea–water solutions at 298.15 K

1997 ◽  
Vol 75 (4) ◽  
pp. 456-464 ◽  
Author(s):  
Andrew W. Hakin ◽  
Lori L. Groft ◽  
Jocelyn L. Marty ◽  
Matthew L. Rushfeldt
Keyword(s):  
Heat Capacities ◽  
Semiempirical Calculation ◽  
Standard State ◽  
Small Peptides ◽  
Apparent Molar Heat Capacities ◽  
Thermodynamics Of Transfer ◽  
Aqueous Urea ◽  
Transfer Thermodynamics ◽  
Transfer Properties ◽  
Calculation Procedures

Relative densities, [Formula: see text] and heat capacity ratios, [Formula: see text] have been measured for aqueous solutions of glycine, glycylglycine, and glycylglycylglycine in aqueous urea solutions containing 1–13 mol kg−1 urea. These data have been used to calculate apparent molar volumes, [Formula: see text] and apparent molar heat capacities, [Formula: see text] which in turn have been used to obtain standard state volumes, [Formula: see text] and standard state heat capacities, [Formula: see text].Volumes and heat capacities of transfer from water to urea have been calculated from our reported standard state data. Heat capacities of transfer of the investigated systems have been modeled using a procedure developed from the semiempirical calculation procedures proposed by Helgeson, Kirkham, and Flowers. Keywords: amino acids, peptides, calorimetry, transfer thermodynamics, HKF theory.

Apparent molar heat capacities and volumes of some aqueous solutions of aliphatic amino acids at 288.15, 298.15, 313.15, and 328.15 K

1994 ◽  
Vol 72 (2) ◽  
pp. 362-368 ◽  
Author(s):  
Andrew W. Hakin ◽  
Michelle M. Duke ◽  
Sheri A. Klassen ◽  
Robert M. McKay ◽  
Kathryn E. Preuss
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Aqueous Solutions ◽  
Equilibrium Constants ◽  
Heat Capacities ◽  
Apparent Molar Volumes ◽  
Protein Chemistry ◽  
Standard State ◽  
Apparent Molar Heat Capacities ◽  
Molar Volumes

The thermodynamics of amino acid systems are key to the understanding of protein chemistry. We have found that many previous studies of the apparent molar volumes and heat capacities of aqueous solutions of amino acids were conducted at the standard temperature of 298.15 K. This does not allow for the fact that most biological processes occur at temperatures removed from this standard condition.In an attempt to address this imbalance we have measured densities and heat capacities for aqueous solutions of glycine, L-alanine, L-serine, and L-threonine at 288.15, 298.15, 313.15, and 328.15 K using a Picker flow microcalorimeter. Apparent molar volumes and heat capacities, and the associated standard state partial molar properties have been calculated. Constant pressure variations of revised Helgeson, Kirkham, and Flowers equations have been fitted to calculated standard state volumes and heat capacities over the temperature range 288.15 to 328.15 K. These equations may be used to estimate standard state volumes and heat capacities, and hence equilibrium constants, for aqueous amino acid systems at higher temperatures.

The volumetric and thermochemical properties of aqueous solutions of L-valine, L-leucine, and L-isoleucine at 288.15, 298.15, 313.15, and 328.15 K

1994 ◽  
Vol 72 (6) ◽  
pp. 1489-1494 ◽  
Author(s):  
Michelle M. Duke ◽  
Andrew W. Hakin ◽  
Robert M. McKay ◽  
Kathryn E. Preuss
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Aqueous Solutions ◽  
Constant Pressure ◽  
Heat Capacities ◽  
Thermochemical Properties ◽  
Acid System ◽  
Standard State ◽  
Apparent Molar Heat Capacities ◽  
Fitting Procedures

Densities and volumetric heat capacities have been measured for aqueous solutions of L-valine, L-leucine, and L-isoleucine at 288.15, 298.15, 313.15, and 328.15 K. These data have been used to calculate apparent molar volumes, [Formula: see text] and apparent molar heat capacities, [Formula: see text] which in turn have been used to obtain standard state volumes, [Formula: see text] and standard state heat capacities, [Formula: see text] for each aqueous amino acid system. Helgeson, Kirkham, and Flowers equations, for neutral organics in water, have been used to model the calculated standard state volumes and heat capacities of the amino acids as a function of temperature at constant pressure. The results of our fitting procedures may be used to predict the behaviour of [Formula: see text] and [Formula: see text] for the selected amino acid systems outside of the temperature range utilised in this investigation.

Densities and apparent molar volumes of aqueous aluminum chloride. Analysis of apparent molar volumes and heat capacities of aqueous aluminum salts in terms of the Pitzer and Helgeson theoretical models

1986 ◽  
Vol 64 (2) ◽  
pp. 353-359 ◽  
Author(s):  
Leslie Barta ◽  
Loren G. Hepler
Keyword(s):  
Aqueous Solutions ◽  
Interaction Model ◽  
Partial Molar Volumes ◽  
Theoretical Models ◽  
Heat Capacities ◽  
Apparent Molar Volumes ◽  
Standard State ◽  
Apparent Molar Heat Capacities ◽  
Molar Volumes ◽  
Aqueous Aluminum

Densities of aqueous solutions of AlCl3 (containing dilute HCl) have been measured at 10, 25, 40, and 55 °C with results that have led to defined apparent molar volumes. We have used the Pitzer ion interaction model as the basis for analyzing these apparent molar volumes to obtain standard state (infinite dilution) partial molar volumes of AlCl3(aq) at each temperature. We have also made similar use of apparent molar heat capacities of aqueous solutions of AlCl3–HCl and Al(NO3)3–HNO3 from Hovey and Tremaine to obtain standard state partial molar heat capacities of AlCl3(aq) and Al(NO3)3(aq) at these same temperatures. Finally, the standard state partial molar volumes and heat capacities have been used with the Helgeson–Kirkham semi-theoretical equation of state for aqueous ions to provide a basis for estimating the thermodynamic properties of Al3+(aq) at high temperatures and pressures.

Apparent molar heat capacities and volumes of unsaturated heterocyclic solutes in aqueous solution at 25 °C

1980 ◽  
Vol 58 (7) ◽  
pp. 704-707 ◽  
Author(s):  
Octavian Enea ◽  
Carmel Jolicoeur ◽  
Loren G. Hepler
Keyword(s):  
Aqueous Solution ◽  
Aqueous Solutions ◽  
Heterocyclic Compounds ◽  
Infinite Dilution ◽  
Heat Capacities ◽  
Group Additivity ◽  
Standard State ◽  
Apparent Molar Heat Capacities ◽  
Partial Molar Heat Capacities

Measurements at 25 °C with flow calorimeters and densimeters have led to heat capacities and densities of aqueous solutions of 15 unsaturated heterocyclic compounds containing nitrogen. From the results of these measurements we have obtained apparent molar heat capacities and volumes of the solutes. Extrapolations to infinite dilution have led to corresponding standard state apparent and partial molar heat capacities and volumes, which have been analyzed in terms of atomic and group additivity relationships.

Thermodynamics of aqueous carbon dioxide and sulfur dioxide: heat capacities, volumes, and the temperature dependence of ionization

1983 ◽  
Vol 61 (11) ◽  
pp. 2509-2519 ◽  
Author(s):  
José A. Barbero ◽  
Loren G. Hepler ◽  
Keith G. McCurdy ◽  
Peter R. Tremaine
Keyword(s):  
Experimental Data ◽  
Carbon Dioxide ◽  
Infinite Dilution ◽  
Heat Capacities ◽  
Standard State ◽  
Apparent Molar Heat Capacities ◽  
Experimental Heat ◽  
Chemical Relaxation ◽  
Vibrating Tube Densimeter ◽  
New Equation

A flow microcalorimeter and vibrating tube densimeter were used at 25 °C to obtain apparent molar heat capacities and volumes of aqueous NaHCO3, KHCO3, NaHSO3, and KHSO3, from 0.1 to 1.0 mol kg−1, aqueous CO2 from 0.01 to 0.10 mol kg−1 and aqueous SO2 from 0.045 to 2.0 mol kg−1. The contribution of "chemical relaxation" (changes in equilibrium state and enthalpy due to change in temperature) to the experimental heat capacities of aqueous SO2 required special attention, leading to the derivation of a new equation for calculating this effect. Standard state values for the heat capacities and volumes of aqueous CO2, SO2, HCO3−, and HSO3− were obtained from the apparent molar properties by extrapolation to infinite dilution. Combining these results with other thermodynamic data from the literature gave estimates of log K1b the equilibrium constant for the first neutralization of CO2 and SO2, at high temperatures. The results for CO2 reproduce very accurate literature values to within 0.2 at 200 °C. The expression for the reaction [Formula: see text] log K1b = 22.771 + 2776.0/T–8.058 log T, is consistent with the sparse and limited experimental data.

Calorimetric investigations of aqueous amino acid and dipeptide systems from 288. 15 to 328. 15 K

1995 ◽  
Vol 73 (5) ◽  
pp. 725-734 ◽  
Author(s):  
Andrew W. Hakin ◽  
Michelle M. Duke ◽  
Lori L. Groft ◽  
Jocelyn L. Marty ◽  
Matthew L. Rushfeldt
Keyword(s):  
Amino Acid ◽  
Thermodynamic Properties ◽  
Heat Capacities ◽  
Group Additivity ◽  
Standard State ◽  
Apparent Molar Heat Capacities ◽  
Empirical Modelling ◽  
Temperature Dependences ◽  
Calorimetric Investigations ◽  
Capacity Data

Densities and heat capacities have been measured for aqueous solutions of L-asparagine, L-glutamine, glycylglycine, glycyl-L-valine, glycyl-L-asparagine, and glycyl-DL-leucine at 288.15, 298.15, 313.15, and 328.15 K. These data have been used to calculate apparent molar volumes, V2,ø, and apparent molar heat capacities, Cp,2,ø, which in turn have been used to obtain standard state volumes, [Formula: see text] and heat capacities, [Formula: see text] The semi-empirical modelling procedures of Helgeson, Kirkham, and Flowers have been used to subdivide the calculated standard state volume and heat capacity data into solvation and nonsolvation contributions. The nonsolvation components of the standard state properties are used in group additivity analyses. These analyses yield structural contributions to standard state volumes and heat capacities for the CH(NH2)CO2H, CH2, OH, COOH, CH, CONH2, and CONH groups. The temperature dependences of these contributions are discussed. Some comments are reported concerning the practicality of using the thermodynamic properties of aqueous amino acid and peptide systems as the basis for modelling standard state thermodynamic properties of aqueous protein systems. Keywords: heat capacities, densities, volumes, amino acids, peptides, group additivity.

Apparent and partial molar heat capacities and volumes of aqueous HClO4 and HNO3 from 10 to 55 °C

1989 ◽  
Vol 67 (9) ◽  
pp. 1489-1495 ◽  
Author(s):  
Jamey K. Hovey ◽  
Loren G. Hepler
Keyword(s):  
Nitric Acid ◽  
Aqueous Solutions ◽  
Perchloric Acid ◽  
Ionic Species ◽  
Heat Capacities ◽  
Standard State ◽  
Apparent Molar Heat Capacities ◽  
Solvent Interaction ◽  
Partial Molar Heat Capacities ◽  
Temperature Dependences

Apparent molar heat capacities and volumes of aqueous solutions containing HClO4 and HNO3 have been determined from 10 to 55 °C. The temperature dependences of the standard state heat capacities and volumes of ClO4− (aq) and NO3− (aq) from 10 to 55 °C were found to be well represented by the following equations:[Formula: see text]Combination of the experimental results with semiempirical equations for ion–solvent interaction has led to predictions of the standard state volumes and heat capacities for these ionic species at higher temperatures. Keywords: heat capacities, volumes, nitric acid, perchloric acid.

Apparent molar heat capacities and volumes of aqueous electrolytes at 25 °C: Cr(NO3)3, LaCl3, K3Fe(CN)6, and K4Fe(CN)6

1979 ◽  
Vol 57 (21) ◽  
pp. 2798-2803 ◽  
Author(s):  
Jan J. Spitzer ◽  
Inger V. Olofsson ◽  
Prem Paul Singh ◽  
Loren G. Hepler
Keyword(s):  
Aqueous Solutions ◽  
Infinite Dilution ◽  
Heat Capacities ◽  
Aqueous Electrolytes ◽  
Standard State ◽  
Apparent Molar Heat Capacities ◽  
Molar Volumes ◽  
High Charge ◽  
Flow Calorimeter ◽  
Partial Molar Properties

We have used a flow calorimeter and a flow densimeter for measurements at 25 °C of heat capacities and densities of aqueous solutions of four electrolytes of high charge type: LaCl3, Cr(NO3)3, K3Fe(CN)6, and K4Fe(CN)6. Results of these measurements have been used for calculating corresponding apparent molar heat capacities and apparent molar volumes, which have been extrapolated to infinite dilution to obtain the corresponding standard state apparent molar and partial molar properties. Uncertainties resulting from extrapolations of heat capacities are discussed. Results of our measurements are compared with those of earlier related investigations.

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