Biological systems vesicles

Many complex systems have been spread on liquid interfaces for a variety of reasons. We begin this chapter with a discussion of the behavior of synthetic polymers at the liquid-air interface. Most of these systems are linear macromolecules however, rigid-rod polymers and more complex structures are of interest for potential optoelectronic applications. Biological macromolecules are spread at the liquid-vapor interface to fabricate sensors and other biomedical devices. In addition, the study of proteins at the air-water interface yields important information on enzymatic recognition, and membrane protein behavior. We touch on other biological systems, namely, phospholipids and cholesterol monolayers. These systems are so widely and routinely studied these days that they were also mentioned in some detail in Chapter IV. The closely related matter of bilayers and vesicles is also briefly addressed. 

The fluidity is one of the most vital properties of biological membranes. It relates to many functions involved in biological system, and effective biomembrane mimetic chemistry depends on the combination of both stability and mobility of the model membranes. However, in the polymerized vesicles the polymer chain interferes with the motion of the side groups and usually causes a decrease or even the loss of the fluid phases inside the polymerized vesicle (72,13). 

Probes based on macrocyclic amines include dansylamidoethylcyclen, which can detect zinc at sub-nanomolar concentrations and probes containing xanthene as the chromophore with an ideal wavelength range for intracellular studies.953,962 It is also important that the sensors can differentiate between the alkali metals, which are present at higher concentrations, and zinc. 2, 7-dichlorofluorescein-based sensors have been used in biological systems and reveal concentrations up to ca. 0.3 mM in hippocampal nerve synaptic vesicles.963... 

In some circumstances, it can be anticipated that continuous lifetime distributions would best account for the observed phenomena. Examples can be found in biological systems such as proteins, micellar systems and vesicles or membranes. If an a priori choice of the shape of the distribution (i.e. Gaussian, sum of two Gaussians, Lorentzian, sum of two Lorentzians, etc.) is made, a satisfactory fit of the experimental data will only indicate that the assumed distribution is compatible with the experimental data, but it will not demonstrate that this distribution is the only possible one, and that a sum of a few distinct exponentials should be rejected. 

Characteristics of biological systems, coupled with the rich chemistry of vanadium in aqueous solutions, make the study of effects of vanadium compounds in living systems difficult. The cell is divided into different organelles and vesicles by mem-... 

In the vesicle suspension of Fig. 8 it was possible to isolate the centers for dihydrogen and dioxygen evolution and thus to avoid cross reactions of S+ and A- with the catalysts for H2 and 02 evolution, respectively. However, it turned out that 02 evolution gradually inhibits the H2 evolution, because oxygen evolved in the outer volume permeates across the membranes and destroys the apparatus for dihydrogen evolution located inside the vesicles. Note, that such a problem also arises for biological systems adapted to provide simultaneous evolution of H2 and Oz [275, 276],... 

In biological systems, the size and shape of smaller components is often controlled (morphogenesis) to produce self-assemblies (e.g., cellular vesicles, viruses, and phages). As noted by Stryer [150] and others [151], many of these biological... 

Quenneville, N.R. and Conibear, E. (2006) Toward the systems biology of vesicle transport. Traffic 7, 761-768. 

Direct proteomic approaches can be used to identify protease enzyme proteins, as well as protein categories in the biological system, that are present in secretory vesicles for neuropeptide production and secretion. Knowledge of the secretory vesicle proteome can advance our understanding of neuropeptide biosynthetic mechanisms that operate within this organelle. 

In this section we review the structural and biochemical aspects of two contrasting biological systems involving silicification in (1) intracellular vesicles and (2) extracellular polysaccharidic matrices. 

What remains to be done is to integrate the ultrathin assemblies into society. This is being tried in many application labs throughout the world which work on LB surface monolayers. One may hope that they succeed in developing useful and stable devices. If this expectation is fulfilled, the whole field will flourish since (cast) monolayers, vesicles, micellar fibres and porous microcrystals can easily be combined and integrated. Much more is to be expected from building workable reaction systems or new materials than from mimicry of biological systems which has already been abandoned by most supra-molecular chemists. 

The ability of membranes to compartmentalize reagents and control the permeation of chemical species may also allow the control of electron transfer in a more sophisticated way within the aggregate bilayer [86]. Photosynthetic processes occur specifically in membranes [87] (thylakoid membranes) so there is continuous interest in mimicking these phenomena with synthetic vesicles [86]. Though a large amount of information is available on the components of biological systems that operate electron transport, the actual mechanism of the process is far from being understood in detail. 

Abstract The aggregation behaviour of biomimetic polypeptide hybrid copolymers and copolypeptides is here reviewed with a particular eye on the occurrence of secondary structure effects. Structure elements like a-helix or / -sheet can induce a deviation from the classical phase behaviour and promote the formation of vesicles or hierarchical superstructures with ordering in the length-scale of microns. Polypeptide copolymers are therefore considered as models to study self-assembly processes in biological systems. In addition, they offer a great potential for a production of novel advanced materials and colloids. 

The general field with which this review is concerned is currently one of the most exciting in chemical physics, the study of kinetic processes in systems of finite size and/or of restricted dimensionality. Problems ranging from the study of organized molecular assemblies (micelles, vesicles, microemulsions), biological systems (cells, microtubules, chloroplasts, mitochondria), structured media such as clays and zeolites, and nucleation phenomena in finite domains are among those under active investigation. 

Biological systems often exhibit spherical symmetry, or something near it. For example, certain cells are assumed to be spherical as are vesicles within cells and synthetic vesicles. Therefore, it is frequently convenient to examine the transport of solutes in a spherical coordinate system. Equation 3-31 can be expressed in spherical coordinates ... 

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