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Motilin-bicelle interactions: membrane position and translational diffusion.

FEBS letters (2003-06-14)
August Andersson, Lena Mäler
ABSTRACT

The interaction between the peptide hormone motilin and bicelles has been investigated by pulsed field gradient-nuclear magnetic resonance methods and by the use of paramagnetic probes. Diffusion coefficients were measured for motilin, the phospholipids with and without motilin, and for tetramethylsilane. The results show that around 90% of motilin is bound to acidic bicelles and 84% of motilin is bound to neutral bicelles. It is found that the apparent bicelle size is reduced by the presence of motilin. This cannot be explained by changes in 1,2-dihexanoyl-sn-glycero-3-phosphatidylcholine solubility. The use of paramagnetic agents to investigate the position of motilin shows that the turn in the N-terminus of motilin is inserted into the bicelle, while the helix most likely resides within the head-group layer.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Tetramethylsilane, ACS reagent, NMR grade, ≥99.9%
Sigma-Aldrich
Tetramethylsilane, electronic grade, ≥99.99% trace metals basis
Sigma-Aldrich
Tetramethylsilane, ≥99.0% (GC)
Supelco
Tetramethylsilane, analytical standard, for NMR spectroscopy, ACS reagent