Infrared reflection-absorption of melittin interaction with phospholipid monolayers at the air/water interface

C. R. Flach, F. G. Prendergast, R. Mendelsohn

Research output: Contribution to journalArticle

52 Scopus citations

Abstract

The interaction of melittin with monolayers of 1,2- dipalmitoylphosphatidylcholine and 1,2-dipalmitoylphosphatidylserine has been investigated with infrared external reflection-absorption spectroscopy. Improved instrumentation permits determination of acyl chain conformation and peptide secondary structure in situ at the air/water interface. The IR frequency of the 1,2-dipalmitoylphosphatidylcholine antisymmetric acyl chain CH2 stretching vibration decreases by 1.3 cm-1 upon melittin insertion, consistent with acyl chain ordering, whereas the same vibrational mode increases by 0.5 cm-1 upon peptide interaction with the 1,2- dipalmitoylphosphatidylserine monolayer, indicative of chain disordering. Thus the peptide interacts quite differently with zwitterionic compared with negatively charged monolayer surfaces. Melittin in the monolayer adopted a secondary structure with an amide I(I') frequency (1635 cm-1) dramatically different from the α-helical motif (amide I frequency 1656 cm-1 in a dry or H2O hydrated environment, amide I' frequency 1645 cm-1 in an H→D exchanged α-helix) assumed in bilayer or multibilayer environments. This work represents the first direct in situ spectroscopic indication that peptide secondary structure in lipid monolayers may differ from that in bilayers.

Original languageEnglish (US)
Pages (from-to)539-546
Number of pages8
JournalBiophysical Journal
Volume70
Issue number1
DOIs
StatePublished - Jan 1996

ASJC Scopus subject areas

  • Biophysics

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