1 research outputs found
A Comparative Structural Study in Monolayers of GPI Fragments and Their Binary Mixtures
Glycosylphosphatidylinositols (GPIs), natural complex glycolipids essential
for a range of biological functions, are poorly understood with regard to
their interactions and arrangements in cellular membranes. To evaluate the
role of the head group in the structure formation in 2D model membranes
(monolayers formed at the soft air/liquid interface), we employed the highly
surface sensitive grazing incidence X-ray diffraction technique to investigate
three GPI-fragments bearing the same hydrophobic part but different head
groups. Condensed monolayers of simple GPI fragments are defined only by
ordered alkyl chains. The monolayers of more complex fragments are
additionally characterized by highly ordered head groups. Due to the strong
H-bond network formed by the head groups, GPI-fragment 3 both segregates and
induces order into a model membrane phospholipid (POPC) that mimics the
liquid-disordered phase of cell membranes. Here, we show that the strong van
der Waals interactions between hydrophobic chains overcome the head group
interactions and dominate the structure formation in mixtures of GPI-fragment
3 with lipids that form liquid-condensed phases. This behaviour can be linked
to the GPIs affinity for the lipid rafts