Specific Interactions of Proteins with Functional Lipid Monolayers—Ways of Simulating Biomembrane Processes

Abstract

The interplay between molecular self-organization and molecular recognition leads to the construction of functional supramolecular systems in which order and mobility are combined and whose function is based on their organization. These fascinating phenomena, for which the living cell is a perfect example, can be understood only if a wide range of scientific disciplines work together. For this purpose, synthetic supramolecular systems can be used to simulate natural biomembrane processes. One example of this is the specific recognition and interaction between membrane-bound ligands and receptor proteins. Thus, the specific interaction of vitamin H (biotin) with the tetrafunctional protein streptavidin in the monolayer leads to 2D crystallization of the protein. Structural analysis shows that the protein is attached to the lipid membrane by two biotin-binding sites, leaving two still free. The opportunity this allows for biotinylated molecules to dock to the protein leads to interesting possibilities for constructing protein-containing functional multilayers. Another example for the simulation of biomembrane processes is the function of enzymes which is coupled to the recognition process. In the interaction of phospholipase A, with lecithin monolayers, specific recognition between enzyme and substrate is followed by an active phase of lipid cleavage and then by aggregation of the enzyme to give domains of regular morphology. Fluorescence microscopy can be used to follow this process directly: an enzyme caught in action. Der Witz ist der Finder und der Verstand der Beobachter.

Structures and Synthesis of Zwitterionic Polymers

“…They found a certain interest as ionomers [12][13][14][15], for fibres due to strong interactions with charged dye stuffs [16][17][18], and as rheology modifiers in aqueous solutions [19], due to their great tolerance to highly saline environments [5]. Continuously increasing interest in polyzwitterions has risen only since the 1980s, when they were recognized as analogs of important biological structures, such as phospholipids that are the major constituents of cell membranes [20][21][22][23][24][25]. Apart from certain alkaloids and hormones such as trigonelline or homarine, other important zwitterionic biological structures are compatible solutes, which are crucial for the osmotic regulation of organisms, such as ectoine or betaine (Scheme 3).…”

Spatio-temporal morphology changes in and quenching effects on the 2D spreading dynamics of cell colonies in both plain and methylcellulose-containing culture media

“…One of these procedures is based upon the dynamic scaling analysis (DSA) of colony fronts [3][4][5][6][7][8][9][10][11][12]. In this approach, the two-dimensional (2D) cell colony front dynamics is characterized through a set of dynamic scaling exponents (α, β, z, the roughness, the growth, and the dynamic exponents, respectively) derived from DSA applied to the colony front profiles and by comparing them with those expected from different complex statistical models [13,14]. These approaches have provided data on non-Euclidean 2D spreading biological interfaces that were interpreted in terms of the standard Kardar, Parisi, and Zhang (KPZ) continuous equation [7,8,12,15].…”

“…In this case, carcinoma cells are softer than normal cells [32] and the mismatch in cell elasticity causes several speed "bursts" in which the cancer cell relaxes from a largely deformed shape and consequently, its translational motion increases. The above-mentioned shows that experimental colony dynamic data, from single cells to cell clusters, are of interest for interpreting the influence of spatio-temporal heterogeneities on the colony spreading mechanism [14], in which structural and dynamic characteristics of the medium interfere with molecular recognition-dependent functionalities [33].…”

Fusogenic supramolecular vesicle systems induced by metal ion binding to amphiphilic ligands

“…Molecular recognition processes provide a powerful tool to induce selective interaction at the interface of vesicular membranes that may result in aggregation, adhesion, and fusion. The development of chemical liposomal systems undergoing such events provides approaches to mimicking biomembrane and biological cellular processes (2)(3)(4)(5). It leads as well to the design of artificial bilayer vesicles presenting a range of novel properties and applications [for instance in materials science (6)].…”