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…

Small unilamellar liposomes from mixed natural and polymeric phospholipids: stability and susceptibility to phospholipase A2.

The concept of the uncorkable liposome composed of phase-separated mixtures of a polymerized phospholipid and an enzymically digestible phospholipid has been investigated, using small unilamellar vesicles composed of mixtures of (polymerized) dienoylphosphatidylcholine (DENPC) and dimyristoylphosphatidylcholine (DMPC). Mixed liposomes, even those containing only 10% DENPC, were much more stable than DMPC liposomes, as indicated by the release of entrapped [3H]inulin or [14C]glucose. DMPC liposomes released entrapped solute on exposure to phospholipase A2, whereas mixed vesicles were resistant. The results are compared with those of an earlier study on monolayers of similar compositions. It …

Binding, Interaction, and Organization of Proteins with Lipid Model Membranes

Model membrane systems are used to investigate protein recognition and binding at interfaces. Fluorescence microscopy results are presented for interactions of the proteins, phospholipase A2 and antifluorescyl IgG, at lipid monolayer interfaces. Total internal reflection fluorescence measurements are used to quantify albumin and IgG adsorption to supported lipid monolayers.

Stability of liposomes composed of polymerizable and/or natural phospholipids

Changing the Mindset in Life Sciences Toward Translation: A Consensus

Participants at the recent Translate! 2014 meeting in Berlin, Germany, reached a consensus on the rate-limiting factor for advancing translational medicine.

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…

Book Review: Controlled Release of Drugs: Polymers and Aggregate Systems. Edited by M. Rosoff

An enzyme caught in action: Direct imaging of hydrolytic function and domain formation of phospholipase A2 in phosphatidylcholine monolayers

AbstractPhospholipase A2, a ubiquitous lipolytic enzyme that actively catalyses hydrolysis of phospholipids, has been studied as a model for enzyme-substrate reactions, as a membrane structural probe, and as a model for lipid-protein interactions. Its mechanism of action remains largely controversial. We report here for the first time direct microscopic observation of the lipolytic action of fluorescently marked phospholipase A2 (Naja naja naja) against phosphatidylcholine monolayers in the lipid phase transition region. Under these conditions, phospholipase A2 is shown to target and hydrolyse solid-phase lipid domains of L-α-dipalmitoylphosphatidylcholine. In addition, after a critical ext…

Mixed monolayers of natural and polymeric phospholipids: structural characterization by physical and enzymatic methods

This study has focused on physical characterization and enzymatic hydrolysis of mixed monolayers of a natural phospholipid substrate and a polymerizable phospholipid analogue. Such a mixed system presents the possibility to stabilize model biomembranes, vary the molecular environment within the layer through polymerization and simultaneously examine these influences on monolayer structure. Phospholipase A2 was used here as a sensitive probe of the molecular environment within these mixed, polymerizable monolayers to complement information obtained from isotherm and isobar data. The results clearly show a strong influence of molecular environment on phospholipase A2 activity, even if differe…

Controlled Release of Drugs: Polymers and Aggregate Systems. Edited by M. Rosoff, VCH Verlagsgesellschaft, Weinheim, 1989, xi, 315 pp., bound, DM 132. - ISBN 3-527-26797-2

Controlled release of drugs: Polymers and aggregate systems. Edited byM. Rosoff, VCH Verlagsgesellschaft, Weinheim, 1989, xi, 315 pp., bound, DM 132.- ISBN 3-527-26797-2

Quenching of fluorescein-conjugated lipids by antibodies. Quantitative recognition and binding of lipid-bound haptens in biomembrane models, formation of two-dimensional protein domains and molecular dynamics simulations

Three model biomembrane systems, monolayers, micelles, and vesicles, have been used to study the influence of chemical and physical variables of hapten presentation at membrane interfaces on antibody binding. Hapten recognition and binding were monitored for the anti-fluorescein monoclonal antibody 4–4-20 generated against the hapten, fluorescein, in these membrane models as a function of fluorescein-conjugated lipid architecture. Specific recognition and binding in this system are conveniently monitored by quenching of fluorescein emission upon penetration of fluorescein into the antibody's active site. Lipid structure was shown to play a large role in affecting antibody quenching. Interes…

Hydrolytic action of phospholipase A2 in monolayers in the phase transition region: direct observation of enzyme domain formation using fluorescence microscopy.

Phospholipase A2, a ubiquitous lipolytic enzyme highly active in the hydrolysis of organized phospholipid substrates, has been characterized optically in its action against a variety of phospholipid monolayers using fluorescence microscopy. By labeling the enzyme with a fluorescent marker and introducing it into the subphase of a Langmuir film balance, the hydrolysis of lipid monolayers in their liquid-solid phase transition region could be directly observed with the assistance of an epifluorescence microscope. Visual observation of hydrolysis of different phospholipid monolayers in the phase transition region in real-time could differentiate various mechanisms of hydrolytic action against …