The dissolution enthalpies of glycine in aqueous solutions of acetamide, N-methylacetamide, N,N-dimethylacetamide, N-ethylformamide,
N,N-diethylformamide and N,N-diethylacetamide were measured at 298.15 K. The enthalpic pair interaction coefficients of glycine
zwitterion-amide molecules were determined by using standard solution enthalpies of glycine in water and aqueous solutions
of amides. The additivity of groups concept of Savage and Wood was used to estimate the contribution of each of the functional
groups of the studied amides.
The interaction of Cu2+ to the first 16 residues of the Alzheimer’s amyloid β peptide, Aβ(1–16) was studied by isothermal titration calorimetry at pH 7.2 and 37°C in aqueous solution. The Gholamreza Rezaei Behbehani
(GRB) solvation model was used to reproduce the enthalpies of interactions of Aβ(1–16) with glycine, Gly+Aβ(1–16), and Cu2+ ions, Cu2+ +Aβ(1–16), over the whole range of Cu2+ concentrations. The binding parameters recovered from the solvation model were attributed
to the structural change of Aβ(1–16) due to the glycine and Cu2+ interactions. It was found that there is a set of two identical binding sites for Cu2+ ions. p=2 indicates that the binding has positive cooperativity in the two binding sites. Aβ(1–16) structure is destabilized greatly as a result of binding to Cu2+ ions.
The enthalpic effect due to the interaction between α, β poly(N-hydroxyethyl)-DL-aspartamide (PHEA) and sodium dodecylsulfate (SDS) in aqueous solutions as a function of the surfactant concentration was
measured by the calorimetric technique at various NaCl concentrations. A marked influence of the added electrolyte on the
PHEA-SDS interaction was observed. An analysis of the experimental enthalpies allows to estimate the electrostatic and the
hydrophobic contributions to the enthalpy of interaction between PHEA and SDS micelles. The results were rationalized in terms
of effects due to the screening of the charges residing on PHEA and SDS micelles.
Changes in solvation play a central role in the thermodynamics of non-covalent interactions in solution, especially in water, yet there are relatively few techniques available to probe this unambiguously. Experimental studies of the thermodynamics of biomolecular interactions in water have exposed two significant empirical observations. The first, well known from the very earliest applications of microcalorimetry, is that processes such as protein folding, ligand binding, and protein–protein association almost always occur with a decrease in overall heat capacity of the system (negative ΔCp). This results in a strong temperature dependence of the enthalpy of interaction that has, historically, been usually attributed to solvation changes, though more generally it has been shown to be an inevitable consequence of processes involving the cooperative interaction of multiple weak interactions. More recently using pressure perturbation calorimetry (PPC), we have shown that such interactions in the same systems also occur with significant decreases in molar thermal expansibility (negative ΔE°) that can be related to the loss of solvation during complexation. The apparently strong correlation between ΔCp and ΔE° potentially leads to a generic picture of the thermodynamics of macromolecular interactions in water in which both solvation and conformational fluctuation play a much more prominent role than has been hitherto supposed.
/mol. The enthalpy of solution of nevirapine (Δ sol H (CD) ) in the presence of cyclodextrins (Δ sol H (M)(CD) ) was found to be more exothermic which is attributed to interaction between drug and cyclodextrins. Enthalpyofinteraction between drug and
, Wood , RH ( 1976 ) Enthalpy of dilution of aqueous mixtures of amides, sugars, urea, ethylene glycol and penthaerythritol at 25 °C: enthalpyofinteraction of the hydrocarbon, amide, and hydroxyl functional groups in dilute aqueous solutions . J
, sugars, urea, ethylene glycol, and pentaerythritol at 25 °C: Enthalpyofinteraction of the hydrocarbon, amide, and hydroxyl functional groups in dilute aqueous solutions . J Solut Chem 1976 5 : 733 – 739 10.1007/BF00643457
Calorimetric results are shown in Fig. 6 .The enthalpyofinteraction ( Fig. 7 ), Δ R H , was obtained from an expression fitted to the modified Langmuir equation represented in Eq. 7 [ 14 – 17 ].
where Σ X is the sum of the molar fractions of the