Side-chain conformational thermodynamics of aspartic acid residue in the peptides and achatin-I in aqueous solution.

ABSTRACT: Sequence-position dependence of the side-chain conformational equilibrium of aspartic acid (Asp) residue is investigated for both model Asp peptides (di- to tetra-) and neuropeptide achatin-I (Gly--Phe-Ala-Asp) in aqueous solution. The trans-to-gauche conformational changes on the dihedral angle of C-C(alpha)-C(beta)-C are analyzed in terms of the standard free energy DeltaG(0), enthalpy DeltaH(0), and entropy -TDeltaS(0). The thermodynamic quantities are obtained by measuring the dihedral-angle-dependent vicinal (1)H-(1)H coupling constants in nuclear magnetic resonance over a wide temperature range. When the carboxyl groups of Asp are ionized, DeltaG(0) in the aqueous phase depends by approximately 1-2 kJ mol(-1) on the sequence position, whereas the energy change in the gas phase (absen

SUBMITTER: Kimura T 

PROVIDER: S-EPMC1303905 | biostudies-literature | 2004 Feb

REPOSITORIES: biostudies-literature