Structural changes for the endogenous opioid peptide �-neoendorphin (�-NE) in various solvents were investigated using infrared, NMR, ThT-fluorescence and Dynamic light scattering (DLS) techniques. The peptide structure was studied in aqueous solution, sodium dodecylsulfate (SDS), trifluoroethanol (TFE), and in the presence of the anionic model membrane dipalmitoylglycerophosphoglycerol (DPPG). FTIR with second derivative resolution and curve-fitting methods indicates that �-NE adopts a major �-sheet structure in water and SDS micelles. A substantial reduction of the �-sheet structure is observed in TFE, with an increase in a-helix structure. DLS experiments reveal that �-NE increases the size of DPPG aggregates. ThT-fluorescence results indicate that �-NE adopts a beta-sheet structure while interacting with DPPG in water, in agreement with the FTIR results. The interaction of �-NE with DPPG in TFE are also discussed. Proton NMR spectra shows that the N atom of the amide group of �-NE is involved in the interaction with DPPG.

Solvent-dependent structure of the endogenous opioid peptide β-neoendorphin

245th National Meeting (2013)

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