Virus & Vesicle Fusion
In the course of our studies of supported lipid bilayers, we developed DNA-lipid conjugates as a strategy for gently holding vesicles [217, 235, 237] or bilayers  away from a solid support. These DNA-lipid conjugates can be prepared with the DNA attached to the lipid anchor at either the 3’ or 5’ end. When both anchors of DNA-lipids in interacting membranes are anchored at the same end, membranes are held apart. However, if one is 3’ and the other 5’ anchored, then membranes are brought together creating a system for simulating membrane fusion [279, 292].
These molecules, assemblies and assays are now being applied to probe the kinetics and mechanisms of enveloped virus membrane fusion. Viruses such as influenza, HIV, Zika, Dengue and others are surrounded by a lipid bilayer and we seek to understand how they get into cells. We use single-particle fluorescence microscopy and develop novel model systems. We are currently investigating the role of lipid composition, proximity, content transfer, and viral protein diffusion on fusion dynamics.
About the Figure:
Synthetic DNA-lipid conjugates bind enveloped viruses to target membranes in the absence of receptor. This permits direct testing of whether receptor engagement affects the fusion mechanism as well as a comparison of fusion behavior across viruses with different receptor binding specificities. This DNA-lipid tethering strategy allows the study of viruses where challenging receptor reconstitution has previously prevented single-virus fusion experiments, like in zika virus. Virus particles are bound to target vesicles, and the rates of individual pH-triggered lipid mixing events are measured using fluorescence microscopy.
 "Detecting and controlling dye effects in single-virus fusion experiments", Robert J. Rawle, Ana Villamil Giraldo, Steven G. Boxer, and Peter M. Kasson, Biophysical Journal, 117, 445-452 (2019). [pdf]
 "pH Dependence of Zika Membrane Fusion Kinetics Reveals an Off-Pathway State”, Robert J. Rawle, Elizabeth R. Webster, Marta Jelen, Peter M. Kasson, and Steven G. Boxer, ACS Central Science,
4, 1503-1510 (2018). [pdf] [Commentary]
 "Cholesterol enhances influenza binding avidity by controlling nanoscale receptor clustering", Isabel N. Goronzy, Robert J. Rawle, Steven G. Boxer, and Peter M. Kasson, Chemical Science, 9, 2340-2347 (2018). [pdf]