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. 2014 Aug 14;2014:626719. doi: 10.1155/2014/626719

Table 5.

Protonation constants of dipeptides in water and water-ethanol mixture [Temp. = 25°C and I = 0.1 mol·dm−3 NaCl].

Dipeptides Water 20% E—80% Wc 40% E—60% Wc 60% E—40% Wc
log⁡K 1 log⁡K 2 log⁡K 1 log⁡K 2 log⁡K 1 log⁡K 2 log⁡K 1 log⁡K 2
Gly-Gly 8.15a 3.11b 7.66 3.33 6.92 3.54 6.98 3.81
GlyVal 8.23d 3.15d 7.67 3.52 7.06 3.91 6.92 4.18
GlyLeu 7.91e 3.15e 7.60 3.38 7.17 3.94 7.02 4.22
GlyPhe 7.98d 3.03d 7.62 3.33 6.96 3.65 6.98 3.91
GlyThr 8.50c 3.20c 7.74 3.19 7.07 3.37 7.05 3.67
GlyMet 8.22f 3.11f 7.64 3.32 7.02 3.62 6.96 3.91

Note. E: ethanol; W: water; adata taken from reference [51]; bdata taken from reference [52]; cdata taken from reference [42]; ddata taken from reference [53]; edata taken from reference [54]; fdata taken from reference [55]. log⁡K 1 corresponds to 11 species (i.e., L− + H+⇌ LH); log⁡K 2 corresponds to 12 species (i.e., LH + H+⇌LH2 +). The % is expressed as (volume/Volume).