title: Hydrophobicity-induced pK shifts in elastin protein-based polymers.
abstract: Three polypentapeptides--poly[0.8(GVGVP), 0.2(GEGVP)], poly[0.8(GVGIP), 0.2(GEGIP)], and poly[0.75(GFGVP), 0.25(GEGVP)]--all analogues of the polypentapeptide of elastin--(Val1-Pro2-Gly3-Val4-Gly5)n or poly(VPGVG)--have been prepared to determine the effect of changing the hydrophobicity, i.e., Val1----Ile1 (I) and Val4----Phe4 (F), on the pKa and the temperature dependence of pKa of the Glu (E) residue. Shifts in pKa as large as 1.7 units are observed and the temperature dependence is much steeper for the structure-dependent proximity of the more hydrophobic Ile1 residues to the Glu4 residue. Even though this system is dominated by the inverse temperature transition of hydrophobically driven folding on raising the temperature, the effect of adding 0.15 N NaCl is to suppress the hydrophobicity-induced pKa shift.
authors.affiliation: Laboratory of Molecular Biophysics, University of Alabama, Birmingham 35294.
authors.forename: D W
authors.initials: DW
authors.lastname: Urry
authors.forename: S Q
authors.initials: SQ
authors.lastname: Peng
authors.forename: T M
authors.initials: TM
authors.lastname: Parker
mesh_terms: D000595:Amino Acid Sequence; D004549:Elastin / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry; D011487:Protein Conformation; D013696:Temperature; D014867:Water / Q000737:chemistry
chemical_list: D009842:Oligopeptides; D011108:Polymers; D014867:Water; D004549:Elastin