Thermodynamics of solvation of some small peptides in water at T=298.15K

Hydration of Thiourea and Mono-, Di-, and Tetra-N-Alkylthioureas at Infinite Dilution: A Thermodynamic Study at a Temperature of 298.15 K

“…By plotting the C p ,2 ∞ of N -alkylthioureas as a function of the number of alkyl C atoms, a slope of (88.5 ± 6.8) J·K –1 ·mol –1 was obtained, in very good agreement with that we previously found for mono-, di-, tri-, and tetra- N -alkylureas, (88.9 ± 2.3) J·K –1 ·mol –1 , (Figure ) as well as for N -acetylamino acid amines, (89.3 ± 0.6) J·K –1 ·mol –1 . Similar average C p ,2 ∞ [CH 2 ] values were reported for various monofunctional alkyl componds (89.6 J·K –1 ·mol –1 ) , as well as for N -substituted alkylamides, carboxylic acids, and their sodium salts (90.85 J·K –1 ·mol –1 ) .…”

“…The slopes, representing the solvation enthalpy of the methylene group, were (−4.5 ± 0.7) kJ·mol –1 and (−3.0 ± 0.4) kJ·mol –1 , respectively. Δ solv H m ∞ [CH 2 ] for thioureas appears thus in reasonable agreement with earlier results for various series of homologous alkyl compounds. ,,,,− T(1,1,3,3)MTU was not considered for linearization since its solvation enthalpy strongly deviates from the linear plot (Figure ). The considerably low value of Δ solv H m ∞ [T(1,1,3,3)MTU] should be attributed to both the steric hindrance provoked by bulky methylene groups and the intrinsic nitrogen atom inability to form hydrogen bonds with water.…”

“…The thermodynamic studies of the hydrophobic effect initiated by Frank and Evans in 1945 and continued by Kautzmann showed that the entropic mechanism for association of nonpolar moieties is central for protein folding and stability. To better understand the complex interactions of biomolecules with their environment, the hydration of small model molecules has then been extensively studied. − In this context, properties and hydration of urea and its N -alkyl derivatives, as small model hydrophilic solutes, but also denaturants for proteins, have been widely investigated − in the past decade, while thiourea and N -alkylthioureas have been far less explored. However, great attention has been given to thiourea and its derivatives as enzyme inhibitors, in particular of HIV-1 reverse transcriptase, potential receptors and ionophores for heavy metal cations, and building blocks for anion receptors. , It was shown that hydrogen-bonding ability of the functional group −N(H)–C(=S)–N(H)– can be modulated by the insertion of hydrophobic alkyl substituents. , Moreover, the topography of hydrophobic moieties is expected to play an important role in determining their bonding/hydration as we found for urea and its N -alkyl derivatives. , As a consequence, thiourea and its derivatives are widely utilized in the field of molecular recognition, , while their employment in both crystal assembly and functionalization, as well as for the construction of nanostructured materials, is now explored .…”

Desolvation Penalty for Burying Hydrogen-Bonded Peptide Groups in Protein Folding

“…The calculated values of Δ H solv are based on a fixed value for the peptide group, −14.2 kcal/mol, taken from experimental data for monoamides. However, it is known today that addition of neighboring peptide groups causes this value to decrease drastically because there are electrostatic interactions between peptide group dipoles of neighboring residues, and a calorimetric study of Δ H solv for dipeptide analogues demonstrates this decrease directly. This effect explains a large part of the 2-fold difference.…”

Stability of H‐complexes of nicotinamide nitrogen heteroatom with water and ethanol in mixed solvents by 13C NMR probing

“…A known approach to determination of individual functional groups solvation thermodynamic characteristics is an assumption on molecular fragments contributions additivity. [9][10][11][12][13][14][15][16] However, this conception ignores the combined effect of the functional groups on a molecule. A number of authors report on failure of this approach for some organic molecules classes.…”