Langmuir monolayer approach

Because brain lipids play a key role in the pathogenesis of Parkinson s disease and related S5mucleopathies, it is important to identify which lipids are recognized by a-synuclein and the consequences of a-synuclein binding to these lipids. The exhaustive analysis of a-synuclein-glycosphingolipid interactions by the Langmuir monolayer approach indicated... 

The observation that Langmuir monolayers often exist as phase-separated domains has begun to be exploited as a means to produce LB monolayers with two-dimensional patterns. This approach aims to form, transfer, and stabilize these domains on appropriate substrates by combining the Langmuir-Blodgett method with the covalent bonding aspect of self-assembly. There are a small number of studies, and the possible further functionalization of the domains and use of different combinations of materials make this area promising for the construction of patterned films. 

SECM has been extended successfully to investigate chemical processes at aqueous-air interfaces and Langmuir monolayers supported on them [19,34,93]. Initial work concentrated on molecular transfer processes across the aqueous-air interface, with and without a monolayer of surfactant. A submarine UME (described in section III) was utilized which could approach the air-water interface from below. The first study employed the DPSC mode to investigate the transfer kinetics of electrogenerated Br2, from aqueous... 

This acronym is derived from the names of its originators Brunauer, Emmett and Teller [83]. A major advance relative to the monolayer approach of Langmuir [84] is the incorporation of multilayer adsorption. The BET equation can be written as follows [79],... 

Bright RM, Walter DG, Musick MD, Jackson MA, Allison KJ, Natan MJ (1996) Chemical and electrochemical Ag deposition onto preformed Au colloid monolayers Approaches to uniformly-sized surface features with Ag-like optical properties. Langmuir 12 810-817... 

Zhang, J., C.J. Slevin, C. Morton, P. Scott, D.J. Walton, and P.J. Unwin. 2001. New approach for measuring lateral diffusion in Langmuir monolayers by scanning electrochemical microscopy (SECM) Theory and application. J. Phys. Chem, B 105 11120-11130. 

Langmuir monolayers play some part in the preparation of multi-layer systems, now mostly referred to as self-assembled monolayers or multilayers (SAM s). However, this role is modest because it is difficult to make Langmuir-Blodgett layers sufficiently perfect and stable to function in new materials, such as electronic and bio-mimetic devices. One approach of stabilizing LB films is by working with molecules having double bonds that, after deposition, are polymerized. Such layers are stable enough to serve as a substrate for protein adsorption ). 

Several new techniques have been developed by which it is possible to establish the boundaries between monolayer phases and the nature of the transitions between them. Other approaches have begun to provide direct information about the microscopic structures of monolayer phases. In this section, we will briefly describe these methods and their application to Langmuir monolayers. 

In the recent past, combinatorial chemistry has revolutionized medicinal chemistry and this approach has emerged as a powerful technique to discover novel materials. For the first time, we have attempted to combine Langmuir monolayer and combinatorial chemistry techniques to create proteinlike su-pramolecular structures. We synthesized a peptide lipid library and three sublibraries and studied their monolayer properties at the air-water interface. It was found that the peptide lipid libraries readily formed stable monolayers at the air-water interface and exhibited different binding activities toward carbohydrate molecules from the aqueous subphase. Our study suggests that combinatorial surface chemistry is a possible novel technique in the design and creation of artificial proteins. 

FIG. 2 Cartoon illustrating the difference between the Langmuir monolayer and traditional solution approaches for supramolecular chemistry study. 

From the experimental studies presented here, we conclude that it is possible to introduce the combinatorial technique in the Langmuir monolayer research. The application of lipid libraries instead of the traditional one or a few lipids for monolayer formation provides a unique approach to generating artificial proteins or other molecular receptors. The supramolecular species with proteinlike structures located on the surface of the monolayer can be readily used for biomimetic sensor development after the deposition of the film on a transducer such as an optic fiber. This combinatorial surface chemistry research may become a very important research area in Langmuir and Langmuir-Blodgett film smdies. 

Adsorption isotherms are by no means all of the Langmuir type as to shape, and Brunauer [34] considered that there are five principal forms, as illustrated in Fig. XVII-7. TVpe I is the Langmuir type, roughly characterized by a monotonic approach to a limiting adsorption at presumably corresponds to a complete monolayer. Type II is very common in the case of physical adsorption... 

Ryen, C. M. andZhu, X. Y., "Two-Step Approach to the Formation of Organic Monolayers on the Silicon Oxide Surface, Langmuir,Vol. 17,2001,pp- 5576-5580. 

The Langmuir-Blodged (LB) technique allows one to form a monolayer at the water surface and to transfer it to the surface of supports. Formation of the BR monolayer at the air/water interface, however, is not a trivial task, for it exists in the form of membrane fragments. These fragments are rather hydrophilic and can easily penetrate the subphase volume. In order to decrease the solubility, the subphase usually contains a concentrated salt solution. The efficiency of the film deposition by this approach (Sukhorukov et al. 1992) was already shown. Nevertheless, it does not allow one to orient the membrane fragments. Because the hydrophilic properties of the membrane sides are practically the same, fragments are randomly oriented in opposite ways at the air/water interface. Such a film cannot be useful for this work, because the proton pumping in the transferred film will be automatically compensated i.e., the net proton flux from one side of the film to the other side is balanced by a statistically equal flux in the opposite direction. 

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