Membrane hybrid bilayers

Figure 19.20 Sketch of a mixed hybrid bilayer lipid membrane incorporating a glutamate receptor.121 (Adapted with permission from G. Favero et al., J. Am. Chem. Soc. 2005,127,8103 —8111. Copyright 2005 American Chemical Society.)...

Supported bilayers represent biomimetic layers which can be supported on a range of materials and adapted for the study of biointeractions (protein-protein, lipid-lipid) including molecular recognition, ion-channel transport and intramembrane interactions. This interface type can be separated into the so-called SLBs (supported lipid bilayers), HBMs (hybrid bilayer membranes) and t-BLMs (tethered bilayer membranes). 

Hubbard JB, Silin V, Plant AL (1999) Self assembly driven by hydrophobic interactions at alkanethiol monolayers mechanism of formation of hybrid bilayer membranes. Biophys J 76 A431... 

Mun S, Choi SJ (2009) Optimization of the hybrid bilayer membrane method for immobilization of avidin on quartz crystal microbalance. Biosens Bioelectron 24 2522-2527... 

Favero G, Campanella L, Cavallo S, D Annibale A, Perrella M, Mattei E, Ferri T (2005) Glutamate receptor incorporated in a mixed hybrid bilayer lipid membrane array, as a sensing element of a biosensor working under flowing conditions. J Am Chem Soc 127 8103-8111... 

Mozsolits H, Wirth HJ, Werkmeister J, Aguilar MI (2001) Analysis of antimicrobial peptide interactions with hybrid bilayer membrane systems using surface plasmon resonance. Biochimica Et Biophysica Acta-Biomembranes 1512 64-76... 

Plant AL (1999) Supported hybrid bilayer membranes as rugged cell membrane mimics. Langmuir 15 5128-5135... 

Hosseini A, Barile CJ, Devadoss A, EberspacherTA, Decieau RA, Collman JP (2011) Hybrid bilayer membrane a platform to study the role of proton flux on the efficiency of oxygen reduction by a molecular electrocatalyst J Am Chem Soc 133 11100-11102... 

Different types of mimetic systems of biological membranes including vesicles (spherical phospholipid bilayers), LB monolayers, hybrid bilayers (HBLs) and tethered lipid bilayers were used in SERS investigations. LB films are monomolecular films that can be fabricated from amphiphiles at the water-air interface and transferred to a SERS solid substrate (such as island film). For SERS studies, the target molecule was treated as a dopant in a monolayer matrix formed for example by arachidic acid or phospholipids. Aroca and co-workers applied the LB technique to detect SERRS signal firom a variety of chromophores such as several perylene derivatives and RH6G even in SM level in some cases (Aroca 2006). HBLs are monolayers of phospholipids incorporated into SAM of long-chain thiols such as... 

All of the above-mentioned examples describe organosiloxane hybrid sheet-like structures. However, cell-mimicry requires spherical structures that can form an inner space as a container. Liposomes and lipid bilayer vesicles are known as models of a spherical cell membrane, which is a direct mimic of a unicellular membrane. However, the limited mechanical stability of conventional lipid vesicles is often disadvantageous for some kinds of practical application. 

The results may provide a guidepost for designing hybrid assemblies which are capable of performing effective binding of anionic and hydrophobic guests that are not incorporated into the anionic bilayer membrane itself macrocyclic... 

The CD band intensity originated from the host (8) is enhanced in the bilayer vesicle ([0] -i-1.5 x 10 deg cm dmol at 247 nm) relative to the corresponding value in the HEPES buffer at 30.0 °C. In addition, no CD spectral change was observed for at least one day at 30.0 °C. This result indicates that the four pyridinium moieties bound to the chiral L-valine residues in 8 assume highly restricted conformations in the bilayer membrane. Thus, the hybrid assembly seems to furnish a chiral guest-binding site different from that provided by 8 alone in aqueous media without the vesicle. 

The steroid cyclophane also provides a sizable and well-desolvated hydro-phobic cavity in aqueous media in a manner as observed for the octopus cyclophane. The molecular recognition ability of the steroid cyclophane is inferior to that of the octopus cyclophane in aqueous solution due to the structural rigidity of steroid segments of the former host. When the steroid cyclophane is embedded in the bilayer membrane to form a hybrid assembly, however, the steroid cyclophane becomes superior to the octopus cyclophane with respect to functions as an artificial cell-surface receptor, performing marked guest discrimination. 

Integral proteins are usually free to move in the plane of the bilayer by lateral and rotational movement, but are not able to flip from one side of the membrane to the other (transverse movement). Immunofluorescence microscopy may be used to follow the movement of two proteins from different cells following fusion of the cells to form a hybrid heterokaryon. Immediately after fusion the two integral proteins are found segregated at either end of the heterokaryon but with time diffuse to all areas of the cell surface. The distribution of integral proteins within the membrane can be studied by electron microscopy using the freeze-fracture technique in which membranes are fractured along the interface between the inner and outer leaflets. 

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