Bilayer lipid membranes development

In biological systems molecular assemblies connected by non-covalent interactions are as common as biopolymers. Examples arc protein and DNA helices, enzyme-substrate and multienzyme complexes, bilayer lipid membranes (BLMs), and aggregates of biopolymers forming various aqueous gels, e.g, the eye lens. About 50% of the organic substances in humans are accounted for by the membrane structures of cells, which constitute the medium for the vast majority of biochemical reactions. Evidently organic synthesis should also develop tools to mimic the Structure and propertiesof biopolymer, biomembrane, and gel structures in aqueous media. 

A cumulative success of artificial ion-channel functions by simple molecules may disclose a wide gate for the design of ion channels and possible applications to ionics devices. Incorporation of these channels into bilayer lipid membrane systems may trigger the developments towards ionics devices. The conventional BLM system, however, is not very stable, one major drawback for the practical applications, and some stabilization methods, such as impregnating the material in micro-porous polycarbonate or polyester filters, are required. On the other hand,... 

Use of bilayer lipid membranes as a generic electrochemical transducer is an exciting future for food biosensors. A taste sensor with multichanneled lipid membrane electrode was recently developed (93). The electric patterns generated from the sensor are similar to human response. The sensor can distinguish different brands of beer. More details on the taste sensor can be found in Chapter 16 of this book. 

Due to their simplicity of construction, ease of modification, electrical methods of detection, fast response time and the fact that they are the principal structural component of all biomembranes, conventional bilayer lipid membrane (BLM) arises as an ideal system for biosensor technology [88] and they have been studied regarding the possibility of developing DNA biosensors consisting of a glassy carbon electrode-modified by a BLM with incorporated ssDNA [89]. 

The considerable advance achieved in recent years in the discrete treatment of transport processes is primarily due to the development of the bilayer lipid membranes (BLM) modifiable with various ionophores. The most important results directly concerned with the functioning of excitable membranes are highlighted in Sections 4.2 and 4.3. 

The mechanism oifilm rupture by nucleation of pores has been proposed by Deqaguin and Gutop (99) to explain the breaking of very fliin films, built up from two attached monolayers of amphiphilic molecules. Such are the secondary foam and emulsion films and the bilayer lipid membranes. This mechanism was further developed by Deijaguin and Prokhorov (3, 100, 101), Kashchiev and Exerowa(102—104), Chizmadzhev and coworkers (105— 107), and Kabalnov and Wennerstrom (108). The formation... 

On the other hand, a human body works at a rate of around 20 W, and assuming that the cell potential is of the order of 0.1 V, the effective total current is 200 A. It transpires, therefore, that the current density is 200/(2.7 X 10 °) = 0.74 X 10 A cm , consistent with the order of magnitude of current density which can be developed at bilayer lipid membranes. ... 

Sub-microscopic glass particles (most frequent diameter <0.1 pm) suspended in an electrolyte solution were capable of acting on developing synthetic lipid membranes or pre-formed bilayer lipid membranes by achieving contact with the surface of such membranes and finally entering them (Majer 1971). Rat erythrocytes pre-treated with lipophilic ethyl-3,5,6-tri-0-benzyl d-glucofuranoside emulsified in isotonic phosphate buffer were protected from haemolysis by glass particles in a dose-related manner (Majer 1975). 

Cells exploit bilayer structures to create anatomical boimdaries, eg in the case of cell membranes which are composed of lipids, proteins, and carbohydrates. During the early 1960s researchers demonstrated that certain classes of lipids, especially phospholipids, could be used to form protein- and carbohydrate-free model membranes. Methods were developed for the preparation of supported bilayer lipid membranes (1), and it was discovered that dried thin films of phospholipids spontaneously hydrate to yield lipid vesicles (2). Vesicles have since then been used as model systems for fluid interfaces and biomembranes (3). Practical applications involving vesicles are in the area of cosmetics and pharmaceutics. 

Liposomes are membrane-based supramolecular particles that consist of a number of concentric lipid membrane bilayers separated by aqueous compartments (Figure 13.15). They were developed initially as carriers for therapeutic drugs. Initially, the bilayers were almost exclusively phospholipid based. More recently, non-phospholipid-based liposomes have been developed. 

A general model for the interaction of drags and anesthetics with lipid membranes has been developed by Jorgensen el al. [49], The situation is best described by a multistate lattice model for the main transition of lipid bilayers. The foreign mole-... 

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