Toward Intelligent Materials - Molecular Self-Assembly: Advances and Applications - page 23

13

C-DQF
DRAWS experiments constrained the peptide termini to a bilayer
structural model (Fig. 1.13A).

with the N-terminal lysine out-of-register, solid-state NMR

F} REDOR solid-state NMR
experiments established that the half of the N-terminal lysines
buried within the leaflet interface can be passivated by stoichio-
metric sequestering of trifluoroacetic acid (TFA) (Fig. 1.13B) [24].

13

C{

19

A

9.8Å

5.2Å

B

10Å

Figure 1.13 KLVFFAE and KLVFFAL bilayer models ( ) showing positions

for the acetate carbonyl carbons (gray spheres). The anti-
parallel out-of-register peptide configuration places the
distance of the solvent-exposed acetates at 9.8 Å, which is
too far to be detected by solid-state NMR, and restricts the
measured 13 CO- 13 CO distance of 5.2 Å to the bilayer interface
[24]. (

A

) Bilayer model of tube wall composed of anti-parallel
out-of-register

B

β

-sheets. N-terminal lysines are colored blue
and hydrophobic residues, including the C-terminal leucine
or protonated glutamate, are colored gray. Gray shading
highlights the individual leaflets. The high density of positive
charge at the bilayer interface is passivated by TFA counter-
ions (space filling with fluorine - green, oxygen - red, and
carbon - gray).