UV resonance Raman spectroscopy probes the amide II′p band position in short breast milk peptides with antioxidant activity

UV resonance Raman spectroscopic study of six short proline‐containing peptides with antioxidant activity isolated from human breast milk was performed. The amide II′ proline spectroscopic band was used to estimate relative cis trans isomerization state of proline amide bonds in the different peptides. Antioxidant activity of the peptides was determined using 1,1‐diphenyl‐2‐picryl‐hydrazyl (DPPH) assay and linoleic acid emulsion assay. Although no clear correlation between the amide II′p position and antioxidant activity of the peptides was observed, they both were found to be sensitive to the presence and/or relative position of proline and tyrosine residues in the peptide. Copyright © 2011 John Wiley & Sons, Ltd.     

The effects of L‐ to D‐isomerization and C‐terminus deamidation on the secondary structure of antimicrobial peptide Anoplin in aqueous and membrane mimicking environment

UV resonance Raman spectra of the antimicrobial peptide (AMP) Anoplin (L ‐Anoplin‐NH₂) and two of its derivatives (enantiomer D ‐Anoplin‐NH₂ and C‐terminus deamidated L ‐Anoplin‐OH) were measured in aqueous buffer solution and in membrane‐mimetic environments including 2,2,2‐trifluoro ethanol (TFE), zwitterionic lipid dipalmitoylglycerophosphocholine (DPPC) and anionic lipid dipalmitoylglycerophosphoglycerol (DPPG) vesicle solutions. All three peptides were found to adopt random‐coil/β turn‐like conformation in aqueous solution over the temperature range of 1–60 °C. The conformation was found to become more α‐helical in membrane‐mimetic solutions such as TFE and DPPG but not in DPPC for all Anoplin derivatives. The data demonstrate that Anoplin preferentially binds to the anionic over the zwitterionic model cell membranes. Results also showed that deamidation does not change the conformation of L ‐Ano‐NH₂ very significantly, but does alter membrane rupturing and antimicrobial activities thus confirming that it is the physicochemical properties rather than the peptide conformation that define the mechanism of AMP action. Copyright © 2010 John Wiley & Sons, Ltd.