The pressure tolerance of different poly-L-lysine conformers in aqueous solution: Infrared spectroscopy and two-dimensional correlation analysis

摘要

Poly-L-lysine can form either of three different conformers as a-helix, anti-parallel P-sheet and random coil stably under appropriate conditions. In buffer solution poly-L-lysine exists in a random coil at about pH 4, an a-helix above pH 12, and transforms from a-helix to P-sheet when the sample is heated to 46 °C for 30 min. The effects of elevated hydrostatic pressure on three different initial conformers of poly-L-lysine are investigated with Fourier transform infrared spectroscopy and two-dimensional correlation analysis. Changes observed in the amide I' band indicate that the a-helix conformer undergo hydration enhancement at low pressure (<400 MPa), then gradually transition into an α'-helix. Two initial conformers, the β-sheet and random coiled polypeptide, undergo conformational changes to an a-helix at low pressure and to an α'-helix at high pressure. Moreover, the conversion occurred at a lower pressure for the β-sheet (~250 MPa) than for the a-helix (~300 MPa) and the random coil (～850 MPa).