Igli?? Advances in Planar Lipid Bilayers and Liposomes

1. Auflage 2014
ISBN: 978-0-12-419959-0
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: 6 - ePub Watermark

E-Book, Englisch, Band Volume 20, 238 Seiten

Reihe: Advances in Planar Lipid Bilayers and Liposomes

Although the origin and the basic meaning of the terms 'planar lipid bilayers' and 'liposome' have not changed during the years, the present advances in the scientific, technological, biomedical and consumer product fields are remarkable. Ever since its launch the 'Advances in Planar Lipid Bilayers and Liposomes' (APLBL) has provided a global platform for a community of researchers having very broad scientific interests in theoretical, experimental and simulation studies on lipid and cell membrane micro and nanostructures. Ranging from artificial lipid membranes to cell membranes, controlled release of functional molecules, drug delivery to cancer cells, pharmaceutical formulations to food products, the applications are simply enormous. An assortment of chapters in APLBL represents both an original research as well as comprehensives reviews written by world leading experts and young researchers. - Gives a survey on recent theoretical as well as experimental results on lipid micro and nanonanostructures - In addition, the potential use of the basic knowledge in applications like clinically relevant diagnostic and therapeutic procedures, biotechnology, pharmaceutical engineering and food products is presented

Autoren/Hrsg.

Igli??, Ale?

Inhaltsverzeichnis

1;Front Cover;1
2;Advances in Planar Lipid Bilayers and Liposomes;4
3;Copyright;5
4;Contents;6
5;Contributors;10
6;Preface;12
7;Chapter One: Biomimetic Membrane Supported at a Metal Electrode Surface: A Molecular View;14
7.1;1. Introduction;15
7.2;2. sBLM Preparation Methods;16
7.2.1;2.1. Vesicle fusion;16
7.2.2;2.2. Langmuir-Blodgett and Langmuir-Schaefer deposition;21
7.3;3. Potential Drop Across the Membrane and an Estimate of the Electric Field Acting on the Membrane;23
7.4;4. Effect of the Potential Applied to the Gold Electrode on the Membrane Stability: AFM, NR, and Surface-Enhanced Infrared ...;27
7.5;5. Imaging Aggregation of Antibiotic Peptides in a Lipid Membrane;40
7.6;6. Potential-Controlled Changes in the Orientation and Conformation of Peptides and Peripheral Proteins: IR Studies of Gra ...;47
7.7;7. Summary and Conclusions;54
7.8;Acknowledgment;56
7.9;References;56
8;Chapter Two: Lipid Monolayers at the Air-Water Interface: A Tool for Understanding Electrostatic Interactions and Rheology ...;64
8.1;1. Introduction;65
8.2;2. Experimental Approaches on Monolayers;65
8.3;3. Phase Diagrams: Two-Phase Regions;70
8.4;4. Distribution of the Phases in the Plane of the Monolayer;74
8.5;5. In-Plane Interactions and Consequences on Film Effective Rheology;78
8.6;6. Comparison Between Different Model Membranes;83
8.7;7. Summary;85
8.8;Acknowledgments;86
8.9;References;86
9;Chapter Three: Langmuir-Blodgett Approach to Investigate Antimicrobial Peptide-Membrane Interactions;96
9.1;1. Introduction;96
9.2;2. Target Membrane Architecture;98
9.3;3. The Role of Phospholipids;100
9.4;4. Lipid Monolayers;103
9.5;5. Effect of Phospholipid Packing Characteristics and Lipid Phase Transitions on Membrane Stability;108
9.6;6. Visualization of Lipid Films;114
9.7;7. Conclusion;115
9.8;References;116
10;Chapter Four: Divalent Metal Cations in DNA-Phospholipid Binding;124
10.1;1. Introduction;125
10.2;2. DNA-Phospholipid-Divalent Metal Cation Interaction;126
10.3;3. Divalent Metal Cations as a Mediator of DNA-Neutral Phospholipid Bilayer Binding;128
10.3.1;3.1. DNA condensation;128
10.3.2;3.2. DNA thermal stability;131
10.4;4. The Structural Variety of DNA-PC-Me2+ Aggregates;132
10.4.1;4.1. X-ray diffraction on DNA-DPPC-Me2+ aggregates: Effect of temperature;132
10.4.2;4.2. Structural polymorphism of DNA-PC-Me2+ aggregates;135
10.4.3;4.3. DNA-DPPC-Zn2+ aggregates;141
10.5;5. Conclusion;142
10.6;Acknowledgments;143
10.7;References;144
11;Chapter Five: Solid-Like Domains in Mixed Lipid Bilayers: Effect of Membrane Lamellarity and Transition Pathway;150
11.1;1. Introduction;151
11.2;2. Materials and Methods;152
11.2.1;2.1. Preparation of vesicles;152
11.2.2;2.2. Optical microscopy;153
11.2.3;2.3. Wide-angle X-ray scattering;153
11.2.4;2.4. Differential scanning calorimetry;153
11.3;3. Results and Discussion;154
11.3.1;3.1. Phase behavior: Transition temperatures and structures;154
11.3.2;3.2. Shape of solid-like domains;157
11.3.2.1;3.2.1. Effect of transition pathway;161
11.3.2.2;3.2.2. Effect of membrane lamellarity;163
11.4;4. Summary and Outlook;164
11.5;Acknowledgments;165
11.6;References;165
12;Chapter Six: Hexagonal Phase Formation in Oriented DPPC-Melittin Samples: A Small-Angle X-ray Diffraction Study;168
12.1;1. Introduction;169
12.2;2. Materials and Methods;170
12.3;3. Results and Discussion;171
12.3.1;3.1. Characterization of the oriented DPPC-melittin system;171
12.3.2;3.2. Is the hexagonal phase originating from mismatch?;178
12.4;Acknowledgment;180
12.5;References;180
13;Chapter Seven: Probing the Self-Assembly of Unilamellar Vesicles Using Time-Resolved SAXS;184
13.1;1. Introduction;185
13.2;2. Experimental Method;187
13.2.1;2.1. Triggering and synchronization;187
13.2.2;2.2. Stopped-flow device calibration;189
13.2.3;2.3. Time-resolved SAXS;191
13.2.4;2.4. Data analysis;193
13.3;3. SAXS Analysis of Unilamellar Vesicles;195
13.3.1;3.1. Modeling of SAXS from unilamellar vesicles;196
13.3.2;3.2. Radiation damage;197
13.3.3;3.3. Self-assembly of unilamellar vesicles;199
13.3.3.1;3.3.1. Vesicle formation at higher concentration range;201
13.3.3.2;3.3.2. Mechanism for vesicle formation;202
13.3.3.3;3.3.3. Vesicle formation at lower concentration range;203
13.4;4. Summary and Outlook;206
13.5;Acknowledgments;207
13.6;References;208
14;Chapter Eight: Defects in Planar Cell Polarity of Epithelium: What Can We Learn from Liquid Crystals?;210
14.1;1. Introduction;211
14.2;2. Liquid Crystals;213
14.2.1;2.1. Mesoscopic modeling;215
14.2.2;2.2. Topological defects;217
14.3;3. Principles of Pattern Formation in Epithelial Tissues;218
14.3.1;3.1. Mathematical model;219
14.3.2;3.2. Time development of PCP patterns;220
14.3.3;3.3. Defects in PCP patterns;221
14.3.4;3.4. Quantification of order in PCP patterns;221
14.4;4. Results;222
14.4.1;4.1. Behavior of the model;222
14.4.2;4.2. Time evolution of PCP patterns and order quantification;223
14.4.3;4.3. Defects in PCP tissues;225
14.5;5. Discussion;227
14.6;References;228
15;Index;232

Leseproben

Chapter Two Lipid Monolayers at the Air–Water Interface
A Tool for Understanding Electrostatic Interactions and Rheology in Biomembranes
Natalia Wilke1    Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC), Dpto. de Química Biológica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Pabellón Argentina, Ciudad Universitaria, X5000HUA Córdoba, Argentina
1 Corresponding author: email address: [e-mail], [e-mail] Abstract
Monomolecular films of surfactants at the air–water interface are easy to prepare and handle, and enable a broad variety of techniques to be used. As in other model systems mimicking membranes, two phases are observed in several experimental conditions. This chapter compares the results found using this model membrane with other models and describes some of the techniques applicable to lipid monolayers. The factors underlying their texture when two phases coexist are summarized, with special attention to line tension, an important parameter in both nucleation and growth, as well as the final domain shape. Finally, the effects of the presence of two phases on the observed mechanical properties of the film (elastic compressibility and shear viscosity) are detailed. Keywords Models for membranes Diffusion in membranes Membrane potential Lipid domains Compressibility Brewster angle microscopy Single-particle tracking 1 Introduction
When amphiphiles are dissolved in an organic solvent and deposited on a water surface, the solution spreads rapidly to occupy the available area. While the solvent evaporates, the surfactant orientates to minimize contact of its nonpolar regions with water, but maximizes the water contact of its polar region, resulting in a one-molecule-thick surfactant film named “Langmuir monolayer.” These self-structured thin films have been the subject of study for many decades from a fundamental point of view in the fields of biophysics and biology as model biomembranes [1–7] and also as bottom-up 2D-patterning of molecularly thin films for different uses [8–14]. Langmuir monolayers are extremely valuable models for membranes [2,6,7,15,16] since experiments can easily be performed in which the molecular area, surface pressure, temperature, and chemical nature of the subphase are varied, and by this means, a broad set of thermodynamic parameters that characterize the monolayer can be accurately determined [1,17,18]. Although transmembrane processes cannot be studied in monolayers, this system is well suited for studying lateral mixing and structuring mediated by a variety of lipids and proteins which constitute biomembranes [5,19–23]. Using this model membrane, a broad spectrum of techniques can be applied, some of which are detailed in Section 2. These lipid films also enable the diffusing species to be followed over a relatively large area and for a long time. Furthermore, the environment of such molecules can be controlled and also varied in a controlled manner (see Section 5). All of this makes Langmuir lipid monolayers a convenient system for analyzing the influence of domains on the mechanical properties of membranes. The results found using Langmuir monolayers and other model membranes are similar in some cases but not in others, raising the interesting question of which model system is more suitable, the answer to which may depend on the parameter under study (see Section 6). 2 Experimental Approaches on Monolayers
Once Langmuir monolayers are formed, these films can be compressed while the area of the interface and the surface tension are determined, which is usually performed using a Wilhelmy plate made of platinum or paper. The surface pressure “p” can then be calculated as the surface tension of the bare interface minus that of the interface modified by the lipid layer, with the plots of p as a function of the mean molecular area “MMA” (interface area divided by the number of molecules at the interface) being referred to as “compression isotherms.” These experiments have been detailed elsewhere (see, e.g., Refs. [1,4,6]). For most lipid monolayers, the slope of the compression isotherm indicates the film's response under expansion or compression since shear can be neglected [24]. However, for some protein monolayers [13,25] and very cohesive lipids [26,27], the slope of the isotherm depends on the position of the sensor (a rectangular Wilhelmy plate) since the usual compression mode is asymmetric [28] (see Fig. 2.1), and thus the mechanical perturbation made in the film is both a compression–expansion and a shape perturbation. In the case of highly cohesive films, the response under the asymmetric perturbation will be affected by both the shear (G*) and the compressibility (E*) moduli, according to the following equations [28]: *+G*=A0?p??A   (2.1) *-G*=A0?p??A   (2.2) where p|| and p? refer to the surface pressure determined with the sensor positioned parallel or perpendicular to the barriers, respectively (see Fig. 2.1). In turn, G* and E* can be expressed as: *?=G'?+iG??=G'?+i??s?   (2.3) *?=E'?+iE??=E'?+i??d?   (2.4) Figure 2.1 Left: Scheme of a typical experiment with two moving barriers. The two positions of the sensor relative to the movement of the barriers are represented. Right: The area of the film is perturbed sinusoidally, and the response is determined with the sensor at the different positions. In this example, the response shows a nonzero shear behavior, since the amplitudes detected with the sensor at different positions are different. The film is viscoelastic and not purely elastic, since the maximum compression (minimum area) is not synchronized with the maximum surface pressure (see vertical line). Both parameters (G* and E*) are complex numbers with a real (elastic response) and an imaginary (viscous response) part, as is clear in Eqs. (2.3) and (2.4). The imaginary parts arise from the fact that the compression speed is finite, so there may be friction resisting the compression flow, and the resistance is characterized by the compression (dilatational) viscosity, ?d. On the other hand, the shear elastic viscosity, ?s, is the ratio between the shear stress and the rate of shear. In order to obtain each component of G*and E*, a sinusoidal perturbation in the film area may be performed with a frequency ? [25]. An instantaneous response is characteristic of an elastic material, whereas a retarded response indicates viscoelasticity. For most lipids, however, shear can be neglected and the elastic compressibility can be directly obtained by the elastic compressibility modulus ? = - MMA (?p/?MMA). For lipid molecules with high intermolecular cohesion, strong lipid–lipid attractions are present within molecules that form the monolayer, and the resulting film has a high ? value, in the order of 102 mN/m (these are named “liquid-condensed”) or higher (named “solid”) [18]. In contrast, when lipids with low intermolecular interactions are spread at the air–water interface, softer films are formed (compressibility modulus from 101 to 102 mN/m), named “liquid-expanded” monolayers [18]. For intermediate interactions, phase transitions induced by compression can be observed. The phase state can also be modulated by temperature like any 3D-phase state: an increase in temperature decreases the surface pressure of the phase transition from an expanded to a denser phase state. The phase transitions in pure lipid monolayers are first order, since two phases can be detected in the monolayer using different techniques. According to the Gibbs phase rule when applied to 2D systems by Crisp [1], lateral pressure should remain constant during the whole transition of monolayers composed of a pure lipid, and therefore, the compressibility modulus should be zero at equilibrium. However, during the phase transition of pure lipids, the isotherm generally shows a nonzero but low slope (see, e.g., Fig. 2.2A, gray line). Observation of this region of the isotherm (normally called “plateau”) has been reported frequently and studied from different points of view. The simplest explanation given for the lack of constancy of surface pressure during the phase transition is related to the presence of impurities...