Figure 5.

pH dependence of folate solubility in 1 M betaine (□) and water (●). (A) Folate concentration measured by absorbance vs folate composition at pH 5. (B and C) Solution density vs the molal composition at pH 7 and 10, respectively. The data were fit to two solid lines for water and two dashed lines for betaine. The intersection of the lines for each solution condition gave the saturation concentration of folate. The transfer free energies at pH 5, 7, and 10 are −297 ± 22, 89 ± 30, and 500 ± 150 cal/mol, respectively.