Specific recognition and formation of two- dimensional streptavidin domains in monolayers: applications to molecular devices

Abstract By virtue of the high-affinity specific interaction between the vitamin, biotin, and the protein, streptavidin, monolayers of synthetic lipids with biotin headgroups can tightly bind streptavidin at the lipid-water interface. Through this specific recognition fluorescently-labelled streptavidin spontaneously organizes in the plane of the interface to form large protein domains, directly visible in situ by fluorescence microscopy and exhibiting optical anisotropy. Further structural characterization has shown that these domains are two-dimensional protein crystals. Correlation with the known three-dimensional crystal structure of streptavidin indicates that two of streptavidin's fou…

Interaction between biotin lipids and streptavidin in monolayers: formation of oriented two-dimensional protein domains induced by surface recognition.

Highly specific ligand-receptor interactions generally characterize surface recognition reactions. Such processes can be simulated by streptavidin-biotin-specific binding. Biotin lipids have thus been synthesized, and their interaction with streptavidin (or avidin) at the air-water interface was directly shown by measurement of surface pressure isotherms and fluorescence microscopy. These proteins interact with the biotin lipid monolayer via specific binding or nonspecific adsorption. Both phenomena were clearly distinguished by use of the inactivated form of streptavidin. The binding of fluorescein-labeled streptavidin to monolayers was also directly observed by fluorescence microscopy. Th…

Microstructure and lateral diffusion in monolayers of polymerizable amphiphiles

Lipid analogue amphiphilic molecules containing polymerizable units were investigated in monolayers at the air/water interface by using film balance measurements, fluorescence microscopy, and photobleaching techniques. The polymerizable groups (diene-, diyne-, and methacrylate units) were introduced into the hydrophobic alkyl chains or into the polar head of the amphiphilic molecules. In the case of the diene- and diyne-containing compounds the polymerizable units are incorporated into the hydrophobic alkyl chains, enabling them to form a two-dimensional network. Due to the free chain flexibility of the monomers the lateral mobility was comparable to that of saturated lipid analogues and de…

Modeling of Cell Membrane Targeting: Specific Recognition, Binding, and Protein Domain Formation in Ligand-Containing Model Biomembranes

Drug delivery systems are designed to assist, accelerate, and control transport of pharmacologically active agents from sites of administration to specified targets in organs and tissues. So-called controlled drug delivery systems are intended to maintain continuously efficacious drug concentrations in vivo, either locally or systemically, over longer time periods. They should provide constant dosage levels above a minimum level of efficacy yet below mandated toxicity levels — a significant advantage over many conventional systemically administered formulations. Site-specific targeting of drugs, particularly those agents which prove highly toxic in small doses, can be utilized to maintain t…

Microspectroscopy on single domains of phase-separated monolayers

SUMMARY A versatile and inexpensive, but fully equipped apparatus is presented, which enables detailed optical studies on amphiphilic molecules at the liquid-gas interface. Structural and spectroscopic information, particularly in small areas of single domains of phase-separated monolayers, can be achieved by combination of this miniaturized Langmuir trough and spectralphotometer microscope. The potential of this apparatus is demonstrated with some measurements on a diyne-substituted polymerizable lipid analogue at the air-water interface.

Ellipsometric and fluorescence microscopic investigations of a cyclam derivative at the air/water interface

Optical measurements of an acylated azacrown at the air-water interface

In this study, a cyclame derivative bearing four aliphatic chain substituents shows, like many amphiphiles, solid-condensed as well as liquid-expanded phases. In contrast to the classical amphiphiles, the onset of its phase transition is characterized by a bump-like shape whose amplitude is a function of the compression speed. Ellipsometry which is very sensitive to the monolayer physical state changes, and fluorescence microscopy which has contributed significantly to the understanding of the phenomena occurring in the phase transition region have been used to investigate the monolayer behavior of this compound. This study shows that in the liquid-expanded state, the film is homogeneous an…