Tilt and rotation angles of a transmembrane model peptide as studied by fluorescence spectroscopy.
Biophys J
; 97(8): 2258-66, 2009 Oct 21.
Article
in En
| MEDLINE
| ID: mdl-19843458
ABSTRACT
In this study the membrane orientation of a tryptophan-flanked model peptide, WALP23, was determined by using peptides that were labeled at different positions along the sequence with the environmentally sensitive fluorescent label BADAN. The fluorescence properties, reflecting the local polarity, were used to determine the tilt and rotation angles of the peptide based on an ideal alpha-helix model. For WALP23 inserted in dioleoylphosphatidylcholine (DOPC), an estimated tilt angle of the helix with respect to the bilayer normal of 24 degrees +/- 5 degrees was obtained. When the peptides were inserted into bilayers with different acyl chain lengths or containing different concentrations of cholesterol, small changes in tilt angle were observed as response to hydrophobic mismatch, whereas the rotation angle appeared to be independent of lipid composition. In all cases, the tilt angles were significantly larger than those previously determined from (2)H NMR experiments, supporting recent suggestions that the relatively long timescale of (2)H NMR measurements may result in an underestimation of tilt angles due to partial motional averaging. It is concluded that although the fluorescence technique has a rather low resolution and limited accuracy, it can be used to resolve the discrepancies observed between previous (2)H NMR experiments and molecular-dynamics simulations.
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Peptides
/
Models, Chemical
Language:
En
Journal:
Biophys J
Year:
2009
Document type:
Article
Affiliation country:
Netherlands