Total entropy losses of BUT [4-hydroxy-2-butanone], benzamidine, and IPMP [2-methoxy-3-isopropylpyrazine] (TΔSL)

Range ≈ -22 kJ/mol
Organism Generic
Reference Irudayam SJ, Henchman RH. Entropic cost of protein-ligand binding and its dependence on the entropy in solution. J Phys Chem B. 2009 Apr 30 113(17):5871-84. doi: 10.1021/jp809968p. p.5878 right column top paragraphPubMed ID19351118
Method Abstract:"Two theoretical formulations are proposed and compared for the loss of translational and rotational entropy upon protein-ligand binding in water… In the second theory, all molecules including the solvent are confined by their neighbors in mean-field configurational volumes. This [investigators] term a "system-frame" (SF) theory because the configurational space available to all molecules is considered in the reference frame of the whole system."
Comments p.5878 right column top paragraph:” Based on Tables 3 and 4, Table 6 shows the changes in the components of and total SF entropy (eq 21). Water binding to the hydrophobic site in barnase loses effectively no entropy. What it loses in orientational entropy, it gains in vibrational and librational entropy. Binding to the more hydrophilic site of BPTI [bovine pancreatic trypsin inhibitor], it loses 12.1 J K^−1 mol^−1. All other ligands lose the same cratic entropy of 33.4 J K^−1 mol^−1 on binding, whereas the rotational entropy loss depends logarithmically on volume through the number of orientations. These values are modulated only slightly by the changes in vibrational and librational entropies because of the differing strengths of the interactions. Benzene loses the smaller value of 49.9 J K^−1 mol^−1 entropy because its high symmetry and weak interactions mean that it loses no rotational entropy about its z axis. The total entropy losses of BUT [4-hydroxy-2-butanone], benzamidine, and IPMP [2-methoxy-3-isopropylpyrazine] are all very close in the range from −71.3 to −74.4 J K^−1 mol^−1, which corresponds to TΔSL ≈ −22 kJ mol^−1."
Entered by Uri M
ID 112033