title: pH-dependent secondary conformation of the peptide hormone leptin in different buffer solutions.
abstract: The secondary structure of leptin in each different pH buffer solution (pH 5.35, 6.75, 7.58 and 8.45) was first determined by attenuated total reflection (ATR)/Fourier transform infrared (FT-IR) spectrometer with second-derivative, Fourier self-deconvolution and band curve-fitting methods to quantitatively estimate the secondary structure of leptin. The results indicate that pH induced more stretching vibration of CH2 and bending vibration of C-H and/or symmetric stretching of carboxylate of leptin structure in higher pH buffer solution than in lower pH buffer solution. Moreover, the band area of amide I for leptin in the higher pH buffer solution markedly enlarged, suggesting the amide I contour of leptin was very sensitive to pH to alter the secondary conformation of leptin structure. The structural component and composition of amide I band for leptin in both pH 6.75 and pH 7.58 buffer solutions were similar and had 50-52% helical structure including alpha-helix at 1654 cm-1 and 3(10)-helical structure at 1659-1667 cm-1 and 1640 cm-1. Although the secondary structure of leptin in pH 5.35 and 8.45 buffer solutions were also similar, a different structural information was obtained.
authors: Department of Medical Research and Education, Veterans General Hospital-Taipei, Taiwan.
authors: L C
authors: LC
authors: Au
authors: S Y
authors: SY
authors: Lin
authors: M J
authors: MJ
authors: Li
authors: C J
authors: CJ
authors: Ho
mesh_terms: D000818:Animals; D006728:Hormones / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D020738:Leptin; D051379:Mice; D010455:Peptides / Q000737:chemistry*; D017433:Protein Structure, Secondary; D011506:Proteins / Q000737:chemistry*; D011994:Recombinant Proteins / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D006728:Hormones; D020738:Leptin; D010455:Peptides; D011506:Proteins; D011994:Recombinant Proteins