Helix conformation of a small peptide melittin in a methanol-water mixed solvent studied by NMR.
Temperature dependence of the α-helix conformation of bee venom melittin in methanol-water mixed solvents has been examined by NMR, in order to elucidate conformation stability and a phase diagram. At high methanol concentration of 100 - ca. 80 wt.%, melittin forms a full α-helix conformation in the temperature range from 25 °C to 60 °C. At intermediate methanol concentration of ca. 80 - ca. 25 wt.%, it undergoes a thermal transformation from a full α-helix to a partial α-helix. In solutions of low methanol concentrations of ca. 25 - 0 wt.%, partial α-helix monomers and their self-aggregated conformers coexist at low temperatures, and the relative number of the monomers increases with increase in temperature. The monomers turn to a random coil state at high temperatures only below ca. 10 wt. % methanol concentrations. The thermal transitions are discussed from the viewpoint of stability of intra-molecular hydrogen bonds and inter-molecular hydrophobic interactions.
Center for Advanced Instrumental Analysis, Kyushu University, Kasuga, Japan. yoshi@mm.kyushu-u.ac.jp
Yoshinori
Y
Miura
D008555:Melitten / Q000737:chemistry*; D000432:Methanol / Q000737:chemistry*; D019906:Nuclear Magnetic Resonance, Biomolecular; D017433:Protein Structure, Secondary; D012997:Solvents / Q000737:chemistry*; D013696:Temperature; D014867:Water / Q000737:chemistry*
D012997:Solvents; D014867:Water; D008555:Melitten; D000432:Methanol