# Why Do Tethered-Bilayer Lipid Membranes Suit for Functional Membrane Protein Reincorporation?
## 4 Different Types of Tethered-Bilayer Lipid Membranes
### Anchorlipid-tBLMs  
Anchorlipids, also called _telechelics_, were the first to be used for tethering a lipid membrane [31]. The most widely used correspond to thiolipids. _Telechelics_ are composed of three distinct molecular segments: (i) an amphiphile that becomes part of the proximal monolayer of the final bilayer structure (i.e., anchorlipid), (ii) an hydrophilic spacer unit, the \"tether\" that decouples the bilayer from the substrate, (iii) a substrate-specific head group (i.e., a chemical linker to surface), for instance based on thiol, disulfides, lipoic acid, silane, or alike for grafting on gold, silver, silicon oxide, metal supports or mercury electrode [24; 71; 72; 76; 32]. Anchorlipids are mainly archaea analogues thiolipids with two phytanoyl chains that improve the fluidic (hence, sealing) character of the hydrophobic core and a polyethylene glycol as spacer [30; 38; 77; 84; 87; 101; 102; 104; 105; 106; 106; 107; 108; 104; 106; 105; 107; 108; 109; 110; 111; 112; 113; 114; 115; 116; 117; 118; 119; 120; 121; 122; 123; 124; 125; 126; 127; 128; 129; 130; 131; 132; 133; 134; 135; 136; 137; 138; 139; 140; 141; 142; 143; 144; 145; 146; 147; 148; 149; 150; 151]. The hydrophobic moiety of the anchor can also be either saturated C14 (myristoyl) [94; 124; 152; 153] or C16 (palmitoyl) [85; 154], or unsaturated C18:1 (oleoyl) acyl chains [96]. As it is also an essential component of mammalian membranes, cholesterol-based anchors have been synthesized [89; 155; 156; 157; 158]. The chemical structure of each of the different anchorlipids mentioned above is detailed in a recent review [125]. The fabrication of an _anchorlipid-tBLMs_ is in most cases a two-step process, i.e., a \"bottom-up\" method: it begins with the formation of a self-assembled _telechelic_ lipid derivative, covalently linked to the support, thus forming the proximal layer of the final architecture and the second step comprises the formation of the phospholipid bilayer by adding the distal layer on the top of the hydrophobic surface exposed to the bulk aqueous phase. The latter step can be achieved in several ways, such as the well-known Langmuir-Blodgett technique [159], rapid solvent exchange of an organic solution of phospholipids [41; 77; 88; 94; 99; 154] or self-directed fusion of vesicles upon interaction with the substrate [30; 32; 84; 95; 101; 104; 144]. The last mentioned is the most commonly used technique as it is best suited to handle protein-containing vesicles. It is further expected to allow the incorporation of MPs by fusion of vesicles that might contain reconstituted proteins. In another approach, [PERSON] and [PERSON]'s group has proposed to form the distal phospholipid monolayer by simply immersing a tholipid-coated mercury drop in an aqueous electrolyte on the surface of which a lipid film has been previously spread. Thanks to the hydrophobic interactions between the alkyl chains of the thiolipid and those of the lipid, this simple procedure gives rise to a lipid bilayer anchored to the mercury surface via the hydrophilic spacer moiety of the thiolipid. By avoiding the use of vesicles, this procedure excludes any artifacts due to partially fused vesicles and guarantees good seaming properties to the bilayer [146; 148]. This approach has been intensively used to study spontaneous interaction/incorporation from the aqueous solution, of diverse membrane-active peptides presenting phytotoxic, antifungal and anti-bacterial activities [147; 160; 161; 162; 163]. In contrast to polymer supported membranes, thiolipid anchored-tBLMs typically exhibit a high long-term stability and a high electrical resistance value [51] because the proximal leaflet consists entirely of anchor molecules, i.e., it contains no (or minimal) free phospholipids [88].