(19)F-Labeling of Peptides Revealing Long-Range NMR Distances in Fluid Membranes.
NMR distance measurements lie at the heart of structural biology. However, long-range distances could not yet be detected in liquid-crystalline biomembranes, because dipolar couplings are partially averaged by the intrinsic molecular mobility. Using conformationally constrained (19)F-labeled amino acids as reporter groups, we could more than double the accessible interatomic distance range by combining a highly sensitive solid-state multipulse (19)F-NMR scheme with a favorable sample geometry. Two rigid 4F-phenylglycine labels were placed into the helical antimicrobial peptide PGLa embedded in fluid oriented membrane samples. A modified Carr-Purcell-Meiboom-Gill sequence yielded an intramolecular distance of 6.6 Å for the labels spanning one helix turn, and 11.0 Å was obtained when the labels spanned two turns. This approach should now also allow the characterization of conformational changes in membrane-active peptides and of oligomeric assemblies in a biologically relevant lipid environment.
†Institute of Biological Interfaces IBG-2, Karlsruhe Institute of Technology, P.O. Box 3640, 76021 Karlsruhe, Germany.
Stephan L
SL
Grage
‡Institute of Organic Chemistry, Karlsruhe Institute of Technology, Fritz-Haber-Weg 6, 76131 Karlsruhe, Germany.
Xiaojun
X
Xu
†Institute of Biological Interfaces IBG-2, Karlsruhe Institute of Technology, P.O. Box 3640, 76021 Karlsruhe, Germany.
Markus
M
Schmitt
†Institute of Biological Interfaces IBG-2, Karlsruhe Institute of Technology, P.O. Box 3640, 76021 Karlsruhe, Germany.
Parvesh
P
Wadhwani
†Institute of Biological Interfaces IBG-2, Karlsruhe Institute of Technology, P.O. Box 3640, 76021 Karlsruhe, Germany.|‡Institute of Organic Chemistry, Karlsruhe Institute of Technology, Fritz-Haber-Weg 6, 76131 Karlsruhe, Germany.
Anne S
AS
Ulrich
conformationally constrained amino acids; liquid−crystalline phase biomembranes; long-range interatomic distance; membrane-active peptides; monofluorine substituents; solid-state 19F-NMR