TELI
Tethered Enhanced Liposome Immobilisation (TELI)
Lipid bilayer membranes define the boundary of cells and act as hydrophobic barriers preventing solutes from freely diffusing in and out of cells. The study of specific interaction with the lipid bilayer is of great importance in understanding for example the mechanisms behind uptake of drugs, identifying new drug targets, bacterial/viral infections and blood coagulation. The applicability of the TELI technology has been shown in a number of scientific studies; the activation of coagulation factor triggered by interaction of these factors with the lipid bilayer surface has been analysed, the pore formation of the bee-venom melittin has been functionally characterized, the function of a malaria drug target, PfAQP, has been investigated, and passive diffusion of small molecules across liposomal membranes has been studied.
The proprietary TELI-technology is based on the use of cholesterolDNA tags and methodology to immobilize and link layers of liposomes to biosensor surfaces and to each other to form layers. The cholesterolDNA tags are composed of two complementary DNA-strands having two cholesterol molecules at one end and the other end being single-stranded (see below).
For liposome immobilisation, the biosensor surface first has to be functionalized to expose single stranded DNA that is complementary in sequence to the single-stranded part of the cholesterol DNA-tag. First NeutrAvidin molecules are immobilized on the sensor surface, and thereafter complexed with biotinDNA molecules (see below).
The liposomes that are of interest for the analysis will have to be made in your laboratory. They can be made using basically any type of phospholipid that form double-layer membrane liposomes. The liposomes should be made together with the membrane protein of interest to form a proteoliposome. There are different reconstitution protocols for various membrane proteins.
The TELI-method is generic in the way that any type of liposomes can be immobilized to the surface. The cholesterol part of the cholesterolDNA-tag is amphiphilic and is spontaneously incorporated into the lipid bilayer of any type of liposomes. This yields liposomes that now expose a DNA molecule (see below), which can hybridize with the biotinDNA at the sensor surface to produce a monolayer of liposomes at the surface.
Multiple layers of surface-immobilized liposomes can subsequently be produced by linking liposomes, which contain cholesterolDNA-tags that are complementary in sequence.
The resulting measurement on a Biacore instrument does give typical results as shown below.
