Vesicles and Membranes

The process of infection of lupine nodule cells by Rhizobia was examined by the thin-section electron microscopic technique, as well as the freeze-fracture technique. Different membranes such as infection thread membranes, peribacterioid membranes, plasma membranes, membranes of cytoplasmic vesicles, and membranes of the Golgi bodies and ER were stained with uranium-lead, silver, phosphotungstic acid, and ZIO (31). ZIO stained the membranes of the proximal face of the Golgi bodies and endoplasmic reticulum. ZIO staining has given good contrast in thick sections such as a cotyledon cell, a root cell, and an aleurone layer for ER, dictyosomes cisternae, mitochondria, and nuclear envelopes (17,32-37). 

It is interesting to note that rc(l — r.y,/r0) is exactly the area A under [r(t) — r, /ro. Therefore, even if the anisotropy decay is not a single exponential, Dw can be determined by means of Eq. (5.50) in which tc(1 — roo/ro) is replaced by the measured area A. An example of application of the wobble-in-cone model to the study of vesicles and membranes is given in Chapter 8 (Box 8.3). More general theories have also been developed (see Box 5.4). 

M Wallsten, Q Yang, P Lundahl. Entrapment of lipid vesicles and membrane protein-lipid vesicles in gel bead pores. Biochim Biophys Acta 982 47-52, 1989. 

Sackmann, E. (1978). Dynamic molecular-organization in vesicles and membranes. Ber. Bunsen-Gesell. Phys. Chem., 82, 891-909. 

In more sophisticated models, it can be considered that both the singlet-oxygen generation and/or the interaction with the quencher can take place also at the interfaces. In vesicles (and membranes), this includes the inner and outer interfaces, which can present different characteristics. 

The transition of a number of phospholipid chains from an ordered to a disordered state is of direct relevance to the state of the cell membrane - it is a characteristic parameter for each phospholipid. The dynamic molecular organization in vesicles and membranes has been described in detail [15] and is shown schematically in Figure 3.3. Using the thermodynamic DSC technique, changes in phase transition... 

As commonly used, the term viscosity refers to isotropic systems of macroscopic dimensions. The term microviscosity is often used to describe the corresponding properties of the microphases in micelles, vesicles and membranes, despite the fact that this property can be highly anisotropic in these environments. Although am-... 

Table 2. Lateral diffusion coefficients measured for a variety of probes in vesicles and membranes.

The cytoplasmic droplet in bull and ram serum is spherical with a diameter of approximately 3 /x. When viewed by phase contrast microscopy, it has a dark granulated region electron microscopy reveals that this region consists of vesicles and membranous or tubular structures. The concentration of acid phosphatase in droplets is 4.3 /xg nitrophenol liberated per hour per 10 particles, much higher than the activity, 0.2 /xg nitrophenol liberated per hour per 10 spermatozoa. Ribonuclease, acid protease, y3-glueuronidase showed similar ratios. Dott and Dingle (D14) submitted additional information which indicated that in the bull and, to a lesser extent in the ram, the lysosomal enzymes cease to be associated with the spermatozoon during its maturation. 

Several comprehensive reviews on polymerizable lipids and supramolecular structures derived from them appeared between 1985 and 2002 [3,25-31], Consequently, this review focuses on developments in this field during 2000-2008. These include synthesis of new types of polymerizable lipids, creation and characterization of novel poly(lipid) membrane systems, and applications of polymerized vesicles and membranes in chemical sensing, separations science, drug delivery, materials biocompatibility, and other fields. 

The composition of the membrane is dynamic. Sections of membrane form buds that pinch off into vesicles and membrane vesicles formed in the Golgi and elsewhere bring new and recycled components back to the membrane. Individual fatty acyl chains turn over as they are hydrolyzed from the lipids and replaced, and enzymes called flipases transfer lipids between leaflets. 

Although the impact of this molecular-level effect is quite small (negligible in most cases), it can, under some circumstances, produce an appreciable energetic effect—repulsive in the case of two approaching surfaces—that is, it will be difficult to displace the last molecular layers separating the surfaces—or attractive in the separation of two contacting (adhesive) surfaces. These topics will appear again in Chapters 10 (on colloids and colloidal stability), 15 on association colloids micelles, vesicles and membranes), and 19 on adhesion). 

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