Hydration of diglycyl tripeptides with non-polar side chains: a volumetric study

Volumetric characterization of homopolymeric amino acids

“…However, such an estimate is not straightforward because, depending on the model compound used, the changes in volume and compressibility accompanying neutralization of an independently hydrated amino group may be different. For example, the values of Δ V neut and Δ K S neut for neutralization of the amino terminus of triglycine [NHCH 2 (CONHCH 2 ) 2 COO − ] equal 26.5 ± 0.5 cm 3 mol −1 and (67.5 ± 0.9) × 10 −4 cm 3 mol −1 bar −1 , respectively, while the same values for neutralization of the amino terminus in long α,ω‐aminocarboxylic acids [NH(CH 2 ) n COO − ] are 23 ± 1 cm 3 mol −1 and (54 ± 2) × 10 −4 cm 3 mol −1 bar −1 , respectively 65, 66. The observed disparity may reflect the differential interactions of nonpolar alkyl (in α,ω‐aminocarboxylic acids) and polar peptide (in triglycine) groups with the adjacent amino terminus, as well as the differential response of these interactions to neutralization of the amino terminus 66…”

“…For example, the values of Δ V neut and Δ K S neut for neutralization of the carboxyl terminus of glycine (with a single CH 2  group in the molecule) are 6 ± 1 cm 3 mol −1 and (7 ± 2) × 10 −4 cm 3 mol −1 bar −1 , respectively, while increasing to 14.5 ± 1 cm 3 mol −1 and (34.5 ± 2) × 10 −4 cm 3 mol −1 bar −1 , respectively, for 8‐aminooctanoic acid (with seven CH 2  groups) 66. Similarly, Δ V neut and Δ K S neut for neutralization of the carboxyl terminus of triglycine are 10.5 ± 0.5 cm 3 mol −1 and (18.4 ± 0.9) × 10 −4 cm 3 mol −1 bar −1 , respectively, while increasing to 13.5 ± 0.5 cm 3 mol −1 and (25.1 ± 0.9) × 10 −4 cm 3 mol −1 bar −1 , respectively, for GlyGlyIle 65. To rationalize this experimental reality, we have recently proposed that neutralized carboxyl groups are capable of forming aggregates stabilized by hydrogen bonds between the carbonyl oxygen of one solute molecule and the hydroxyl group of another molecule 66.…”

“…Hence, the values of Δ V neut and Δ K S neut in Eqs. (5a) and (5b) are assumed to be equal to (10.5 ± 0.5) cm 3 mol −1 and (18.4 ± 0.9) × 10 −4 cm 3 mol −1 bar −1 , respectively 65. Structural changes in volume, Δ V str , and compressibility, Δ K S str , accompanying coil‐to‐helix transition of poly( L ‐glutamic acid) can be calculated from Eqs.…”

Origins of Pressure-Induced Protein Transitions

“…Understandably, when charged, their solvent volumes will become smaller due to electrostriction. [43][44][45] This will bring about a decrease in the value of ΔV in Eq. (3), even changing its sign from positive to negative, thereby making solvent exposure of charged residues an increasingly favorable event with increasing pressure.…”

Volumetric study of aqueous proline-leucine solutions from (283.15 to 318.15) K

“…Among the already mentioned volumetric properties, the first derivatives of volume namely the molar isobaric expansion and the molar isentropic compression, are the most sensitive to the hydration changes accompanying temperature, pressure, and composition variations [8][9][10][11][12].…”