Review Article

Protonation Equilibria of Biologically Active Ligands in Mixed Aqueous Organic Solvents

Table 8

Protonation constants of some α-amino acids in water and water-dioxane mixtures Temp. = 25°C and  mol·dm−3 NaClO4a.

AAWater10% D—90% W20% D—80% W30% D—70% W40% D—60% W50% D—50% W60% D—40% W

Gly9.582.329.552.419.562.709.582.879.583.159.603.489.623.60
Ala9.702.409.662.529.722.649.682.899.733.109.753.399.783.63
Val9.612.389.562.539.602.689.582.869.603.089.623.439.663.65
Leu9.752.509.592.649.642.809.662.999.703.319.723.559.753.75
Ile9.762.479.722.589.632.749.672.979.653.269.703.559.713.74
Phe9.202.439.152.579.102.649.122.819.153.109.163.369.153.50
Ser9.152.429.072.579.102.629.132.829.163.049.203.179.173.35
Thr9.042.459.022.539.062.609.052.759.072.969.103.189.173.40

Note. D = dioxane, W = water, Val = DL-valine, Ala = DL-alanine, Leu = L-leucine, Ile = L-isoleucine, Phe = DL-phenylalanine, Ser = L-serine, and Thr = L-threonine. aData taken from reference [61]. corresponds to 11 species (i.e., L + H+ LH); corresponds to 12 species (i.e., LH + H+). The % is expressed as (volume/Volume).