摘要:

AbstractThe evolution of the cell has become possible after nature had invented the composite membrane by combining two states of matter: the two‐dimensional liquid crystalline lipid/protein bilayer and the macromolecular network.In the first part we introduce the essential structural features of the cell plasma membrane (case of erythrocyte) and describe their extraordinary mechanical properties. These are unmatched by the technical materials and allow migrating cells to squeeze through narrow gaps of the tissue or of the extracellular protein networks without loss of material or lysis. As an example, how nature manages to alter the structure and function of biomenbranes drastically by minor biochemical signals we consider chemically induced shape changes of cells.In the second part we describe some efforts to mimick mechanical properties of cell membranes with composite membranes of monomeric and polymeric amphiphiles. These model systems exhibit promising new material properties for future applications in chemistry and biotechnolog

ISSN:0003-3146    

DOI:10.1002/apmc.1989.051660101

出版商:Hüthig&Wepf Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractOver the past two decades lipid bilayer membranes have served as effective models for biomembranes. Pure lipid membranes allow investigators to probe the behavior of different classes of lipids in lamellar and nonlamellar phases. Nonlamellar phases are of current interest because of their considerable importance in cellular permeability, fusion, endo‐ and exocytosis. The reconstitution of biological membranes from purified protein and lipid components has proven to be a convenient method for the study of protein‐lipid interactions and membrane protein functionality. The introduction of methods to polymerize lipid bilayers in the early 1980s, now provides researchers with new ways to prepare and characterize model biomembranes. This report summarizes three areas of research on polymerized model membranes: 1) the enhancement of chemical stability and reduction in bilayer permeability by polymerization of single component membranes; 2) the polymerization induced domain formation in two‐component membranes, which is accompanied by membrane destabilization when one of the lipid components prefers a nonlamellar structure; and 3) the successful reconstitution of a purified delipidated membrane protein, rhodopsin, into partially polymerized bilayer membranes with retention of both protein functionality and phospholipid surface biocompatib

ISSN:0003-3146    

DOI:10.1002/apmc.1989.051660102

出版商:Hüthig&Wepf Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractThe function of lipid bilayer membranes crucially depends on their mobility and their ability to incorporate components that, e.g., can change molecular order and dynamics or form channels. Since polymerization increases the stability of model membranes at the expense of their mobility a compromise must be sought. Therefore, the effect of different polymerization schemes on the structure and dynamics of polymer membranes has to be checked. To this end X‐ray scattering, DSC‐thermal analysis and a variety of spectroscopic techniques probing the dynamics on largely different time‐‐‐ and length scales were employed, i.e.2H‐NMR, ESR, fluorescense anisotropy and FRAP. These studies showed that in model membranes polymerized in the hydrophylic region the head group mobility can be controlled by the length and the nature of the spacer connecting it to the polymer backbone. The head group region is much less affected, if the polymerization is achieved in the hydrophobic region. By use of a lipid analogue carrying a polymerizable group on only one of its two alkyl chains, membranes retaining high mobility in the hydrophobic region can be generated. Typical membrane constituents, i.e. cholesterol, gramicidin and ubiquinone can be incorporated and the mixtures show a behaviour similar to natural model membranes, although lateral diffusion of the lipids is frozen as a consequence of the pol

ISSN:0003-3146    

DOI:10.1002/apmc.1989.051660103

出版商:Hüthig&Wepf Verlag    

年代:1989

数据来源: WILEY

ISSN:0003-3146    

DOI:10.1002/apmc.1989.051660104

出版商:Hüthig&Wepf Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractThe lipid bilayers of cell membranes are usually connected to two types of biopolymers: the cytoskeleton and the glycocalix. These structures are not only responsible for the stabilization of the lipid bilayer, they also alter the surface properties of the cells. Among the various attempts to mimick membrane properties using polymeric systems(1), one method is the fixation of amphiphilic polymers via hydrophobic anchor groups to lipid bilayers. In the experiments reported here the influence of amphiphilic polymers on the morphology of giant unilamellar liposomes has been investigated. Therefore a series of amphiphilic polyvinylpyrrolidone and dextran derivatives has been synthesized. The fixation of these polymers to the liposomal membranes could be shown with a fluorescence‐labelled derivative by using epifluorescence microscopy. The polymer‐membrane interaction caused by the insertion of the anchor groups leads to drastic morphological changes in this model membrane system. The exclusive interaction with the outer membrane of multilamellar liposomes could be demonstrated by freeze fracture electron microscopy. In addition, the anchoring of a natural capsular polysaccharide in liposomes has been proven by immunofluorescence. In these experiments, also a clustering (patching) of the antigen caused by the binding of the antibody could be obser

ISSN:0003-3146    

DOI:10.1002/apmc.1989.051660105

出版商:Hüthig&Wepf Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractNotwithstanding their more common beginnings, liquid crystals and molecular biology developed mainly parallel and independently during the last one hundred years.Molecule‐phase relationships on the one and complex static‐dynamic treatments on the other hand seem to forward mutually integrative views in our days.Biomesogen approaches will deepen our insights into the spatio‐temporal coherences of biological systems. They might contribute significantly to the understanding of life proc

ISSN:0003-3146    

DOI:10.1002/apmc.1989.051660106

出版商:Hüthig&Wepf Verlag    

年代:1989

数据来源: WILEY

ISSN:0003-3146    

DOI:10.1002/apmc.1989.051660107

出版商:Hüthig&Wepf Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractRecent studies on ionic distribution in solutions and in suspensions were reviewed. Suspensions of latex particles, which were large enough to be seen under an ultramicroscope, were investigated by the 2‐D Fourier transformation. The micrograph showing ordered structures gave discrete scattering spots, whereas those of disordered arrangements displayed no spots or halos. The two‐state structure gave a limited number of halo, confirming our previous conclusion that the very frequently observed single, broad scattering peak was reminiscent of some kind of ordering of solute species. By using an image data analyser, the crystallization process was shown to follow the Ostwald ripening mechanism. The concurrent study by the quasi elastic light scattering method and by the Fourier analysis gave consistent scattering profiles, which indicated that the ordering phenomena took place in the entire volume of suspensions. The scattering intensity (correctly the lattice factor) was calculated for cubic systems with paracrystalline distortion. The peak intensity was lowered by enhanced distortion, while the peak position itself was not affected. This justifies our previous treatment of the single, broad peak in terms of the Bragg equation. The experimentally found scattering curve was compared with this theoretical calculation; the degree of distortion was evalua

ISSN:0003-3146    

DOI:10.1002/apmc.1989.051660108

出版商:Hüthig&Wepf Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractLyotropic liquid crystalline phases of cellulose derivatives were explored as an analytical tool. Molar mass dependent measurements of the helicoidal cholesteric pitch of a cellulose tricarbanilate/solvent system may be used to determine the molar mass of this derivative by optical means. The compatibility of a ternary liquid crystalline system can be adequately investigated by a study of the supermolecular structure with spectroscopic measurements.

ISSN:0003-3146    

DOI:10.1002/apmc.1989.051660109

出版商:Hüthig&Wepf Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractThe application of carotenoids as natural additives in various water‐based or water‐compatible formulations for the pigmentation of foods and feeds is seriously hampered by their insolubility in aqueous systems.Therefore, in order to develop the full potential of colour strength and to achieve a high degree of bioavailability during gastro intestinal passage, the coarse crystalline material has to be transformed into a microdisperse state.Exemplified with β‐carotene, a novel non‐mechanical process is described that transforms the carotenoids into a colloidal hydrosol characterized by an average particle size of about 0.1 μm.The process is based on the preparation of a transient high temperature solute state of the carotenoid in a water‐miscible solvent, coupled with succeeding rapid aqueous precipitation in the presence of a stabilizing polymer colloid. The obtained hydrosols are characterized by photon‐correlation‐spectroscopy(size), and microelectrophoresis(colloidal stabilization).The bioavailability was tested by monitoring plasma levels of β‐carot

ISSN:0003-3146    

DOI:10.1002/apmc.1989.051660110

出版商:Hüthig&Wepf Verlag    

年代:1989

数据来源: WILEY