Figure 1 From: Membrane interaction and structure of the transmembrane domain of influenza hemagglutinin and its fusion peptide complex Hemagglutinin TMD peptide inserts into membrane bilayer at acidic and neutral pH. (A) The blue shift and enhancement of fluorescence intensity of tryptophan residues in TMD when incubated in DMPC:DMPG vesicles attest to the location of TMD in the membrane hydrophobic milieu. The emission maximum for tryptophan in an aqueous environment is 350 nm. (B) K SV acrylamide quenching measurements also indicate deep insertion of TMD into the membrane interior. The dramatic decrease in K SV in the vesicular dispersion compared with that in PB buffer shows that tryptophan side chains are embedded deep into the membrane. Moreover, a twofold reduction in K SV, as well as decreased K SV on neutralization, upon incubating in PC:PG vesicles at pH 5.0 compared with that at pH 7.4 suggests that the TMD penetration is deeper at acidic pH.Back to article page