Reorientation of the helix of the tryptophan-rich gp41W peptide from HIV-1 at interfaces

The glycoprotein gp41 from the Human Immunodeficiency Virus type 1 (HIV-1) has an amino acid sequence enriched in tryptophan residues, the so-called gp41W peptide (i.e., KWASLWNWFNITNWLWYIK) and plays a crucial role in HIV-1 host cell infection. Using the coupling of Second Harmonic Generation targeting the tryptophan residues with lateral surface tension measurements, we investigate the interaction of gp41W with a neat air/water and a lipid/water interfaces. At the air/water interface, gp41W presents a well-defined orientation and this orientation is strongly modified at the lipid/water interface, depending on the surface pressure. These results show that this strategy is well suited to monitor tryptophan containing α-helices orientation at lipid/water interfaces