2 research outputs found
Interactions and Translational Dynamics of Phosphatidylinositol Bisphosphate (PIP<sub>2</sub>) Lipids in Asymmetric Lipid Bilayers
Phosphatidylinositol phosphate (PIP)
lipids are critical to many
cell signaling pathways, in part by acting as molecular beacons that
recruit peripheral membrane proteins to specific locations within
the plasma membrane. Understanding the biophysics of PIP–protein
interactions is critical to developing a chemically detailed model
of cell communication. Resolving such interactions is challenging,
even in model membrane systems, because of the difficulty in preparing
PIP-containing membranes with high fluidity and integrity. Here we
report on a simple, vesicle-based protocol for preparing asymmetric
supported lipid bilayers in which fluorescent PIP lipid analogues
are found only on the top leaflet of the supported membrane facing
the bulk solution. With this asymmetric distribution of lipids between
the leaflets, the fluorescent signal from the PIP lipid analogue reports
directly on interactions between the peripheral molecules and the
top leaflet of the membrane. Asymmetric PIP-containing bilayers are
an ideal platform to investigate the interaction of PIP with peripheral
membrane proteins using fluorescence-based imaging approaches. We
demonstrate their usefulness here with a combined fluorescence correlation
spectroscopy and single particle tracking study of the interaction
between PIP<sub>2</sub> lipids and a polycationic polymer, quaternized
polyvinylpyridine (QPVP). With this approach we are able to quantify
the microscopic features of the mobility coupling between PIP<sub>2</sub> lipids and polybasic QPVP. With single particle tracking
we observe individual PIP<sub>2</sub> lipids switch from Brownian
to intermittent motion as they become transiently trapped by QPVP