The Influence of β-Alanine and 4-Aminobutyric Acid Residues on the Solubility of Peptides Containing Them

Article abstract of DOI:10.1246/bcsj.66.2006

The influence of unnatural amino acid residues, i.e., β-alanine (β-Ala) and 4-aminobutyric acid (γ-Aba) residues, on the solubility of peptides containing them was studied in organic solvents.The difference between the solubilities of peptides containing β-Ala, γ-Aba, Pro, Gly, Leu, and Asp(OBzl) was investigated by the solvent titration method by use of IR absorption spectra.The order of their solubilities is as follows, peptides containing Pro>β-Ala>γ-Aba>Asp(OBzl)>Leu>Gly.The extreme high solubility of peptides containing Pro residues is explained by the concept of "Peptide Segment Separation" caused by the tertiary peptide bond of the Pro residue.The high solubility of peptides containing β-Ala or γ-Aba residues is believed to be due to the difference of the geometries of the Gly, β-Ala, and γ-Aba residues.Their effective concentration seemed to be less important than their geometry.The role of β-Ala and γ-Aba residues in the solubility of peptides is similar to the role of Pro residues rather than Asp(OBzl), Gly, and Leu residues.