Envelope membrane

Spira.1- Wound Modules. Spiral-wound modules were used originally for artificial kidneys, but were fuUy developed for reverse osmosis systems. This work, carried out by UOP under sponsorship of the Office of Saline Water (later the Office of Water Research and Technology) resulted in a number of spiral-wound designs (63—65). The design shown in Figure 21 is the simplest and most common, and consists of a membrane envelope wound around a perforated central coUection tube. The wound module is placed inside a tubular pressure vessel, and feed gas is circulated axiaUy down the module across the membrane envelope. A portion of the feed permeates into the membrane envelope, where it spirals toward the center and exits through the coUection tube. 

Fig. 22. Multileaf spiral-wound module, used to avoid excessive pressure drops on the permeate side of the membrane. Large, 30-cm diameter modules may have as many as 30 membrane envelopes, each with a membrane area of about 2 m. ...

The interiors of rhodopseudomonad bacteria are filled with photosynthetic vesicles, which are hollow, membrane-enveloped spheres. The photosynthetic reaction centers are embedded in the membrane of these vesicles. One end of the protein complex faces the Inside of the vesicle, which is known as the periplasmic side the other end faces the cytoplasm of the cell. Around each reaction center there are about 100 small membrane proteins, the antenna pigment protein molecules, which will be described later in this chapter. Each of these contains several bound chlorophyll molecules that catch photons over a wide area and funnel them to the reaction center. By this arrangement the reaction center can utilize about 300 times more photons than those that directly strike the special pair of chlorophyll molecules at the heart of the reaction center. 

Plant cells contain a unique family of organelles, the plastids, of which the chloroplast is the prominent example. Chloroplasts have a double membrane envelope, an inner volume called the stroma, and an internal membrane system rich in thylakoid membranes, which enclose a third compartment, the thylakoid lumen. Chloroplasts are significantly larger than mitochondria. Other plastids are found in specialized structures such as fruits, flower petals, and roots and have specialized roles. 

In some viruses, the capsid is surrounded by a lipid membrane (envelope), which is derived from the host cell membrane at the site of vims budding. The membrane contains viral envelope glycoproteins as well as host cell membrane proteins. 

Finally, during budding, HIV-1 may also incorporate into its membrane envelope a variety of different molecules, including proteins that may subsequently interact with their counterparts on the host cell membrane (reviewed in ref. 192), resulting in intracellular signaling and facilitation of virus fusion (193,194). However, the incorporation of cell membrane-derived molecules does not appear to be an absolute requirement for virus entry (195), indicating the leading role of CD4 and the coreceptor for any such mechanism. However, this phenomenon may account for lower levels of inhibition when the effects of mutant CD4 and/or chemokine receptor are studied. 

In plants, the photosynthesis reaction takes place in specialized organelles termed chloroplasts. The chloroplasts are bounded in a two-membrane envelope with an additional third internal membrane called thylakoid membrane. This thylakoid membrane is a highly folded structure, which encloses a distinct compartment called thylakoid lumen. The chlorophyll found in chloroplasts is bound to the protein in the thylakoid membrane. The major photosensitive molecules in plants are the chlorophylls chlorophyll a and chlorophyll b. They are coupled through electron transfer chains to other molecules that act as electron carriers. Structures of chlorophyll a, chlorophyll b, and pheophytin a are shown in Figure 7.9. 

Influenza virus particles are spheroidal and approximately 100 nm in diameter. The outer-membrane envelope contains 500 copies of hemagglutinin (HA) trimers and 100 copies of neuraminidase tetramers. The hemagglutinin constitutes the receptor sites for a-sialoside ligands. X-ray analyses show that the three sialic acid binding pockets reside 46 A apart, each trimer being separated on the virion surface by about 65-110 A [42],... 

If microorganisms cross this barrier, the membranes enveloping the brain - the meninges — can become infected, resulting in meningitis. 

Cell fusion—Merging of two cells so that they are contained with a single membrane envelope. 

The influenza neuraminidase is one of two major glycoproteins located on the influenza virus membrane envelope (the other one is haemagglutinin, HA). As the name suggests. 

Unlike in bacteria and fungi, viruses do not have a protective coat that separates essential proteins and nucleic acids from the environment. The majority of viruses consist of nucleic acid polymers (DNA or RNA) enclosed within a protein coat (capsid). Sometimes, viruses pick up a lipid membrane (envelope) from the host cell that surroimds the capsid. The average size of viral particles is in the range 10-300 nm. The most common... 

Conventional freeze-fracture replicas revealed the presence of the two membranes enveloping the hydrogenosomes presenting a different number and distribution of intramembranous particles (Fig. 7a-c) (Benchimol et al. 1996a Benchimol 2001). Four fracture faces were identified two concave faces representing the P faces of the outer and the inner membranes and two con-... 

Genome DNA with nonhistone protein genome in nucleoid, not surrounded by membrane DNA complexed with histone and nonhistone proteins in chromosomes chromosomes in nucleus with membranous envelope... 

Verma, D.P.S., Kazazian, V., Zogbi, V. Bal, A.K. (1978). Isolation and characterization of the membrane envelope enclosing the bac-teroids in soybean root nodules. Journal of Cell Biology 78, 919-36. 

Fig. 6.10. In vivo multiplex CARS microspectroscopy of a NIH 3T3-L1 fibroblast cell in the high-wavenumber region where C-H stretch vibrations reside. A CARS image revealing the intracellular distribution of constituents with high densities of lipids, such as the membrane envelope of the nucleus and intracellular lipid droplet (LD) organelles. Typical MEM-reconstructed Raman spectra taken for (B) a single LD organelle that is indicated by the arrow in A, (C) the nucleus, and (D) the cytoplasm. The spectrum exposure time was 0.3 s...

Potentized homeopathic drugs are capable of producing effects on both prokaryotic and eukaryotic cells. Prokaryotic cells are usually smaller in size (1 - 10 pm) than eukaryotic ones (5 - 100 pm). Membrane-bound organelles like mitochondria, endoplasmic reticulum, Golgi complexes etc. are present in eukaryotic cells but absent in prokaryotic ones. While eukaryotic cells have nucleus containing DNA with histone and non-histone proteins in chromosoms, prokaryotic cells have no nucleus and their DNA with non-histone proteins lies in nucleoid without any membranous envelope. However, both types of cells are covered by plasma membrane with some common features. 

Figure 3.39 Schematic of a plate-and-frame module. Plate-and-frame modules provide good flow control on both the permeate and feed side of the membrane, but the large number of spacer plates and seals lead to high module costs. The feed solution is directed across each plate in series. Permeate enters the membrane envelope and is collected through the central permeate collection channel [111]...

Small laboratory spiral-wound modules consist of a single membrane envelope wrapped around the collection tube, as shown in Figure 3.42. The membrane area of these modules is typically 0.2 to 1.0 m2. Industrial-scale modules contain several membrane envelopes, each with an area of 1-2 m2, wrapped around the central collection pipe. The multi-envelope design developed at Gulf General Atomic by Bray [113] and others is illustrated in Figure 3.43. Multi-envelope... 

Figure 3.42 Exploded view and cross-section drawings of a spiral-wound module. Feed solution passes across the membrane surface. A portion passes through the membrane and enters the membrane envelope where it spirals inward to the central perforated collection pipe. One solution enters the module (the feed) and two solutions leave (the residue and the permeate). Spiral-wound modules are the most common module design for reverse osmosis and ultrafiltration as well as for high-pressure gas separation applications in the natural gas industry...

Table 3.5 Typical membrane area and number of membrane envelopes for 40-in.-long industrial spiral-wound modules. The thickness of the membrane spacers used for different applications causes the variation in membrane area...

In the early 1960s and 1970s, the in-line plate-and-frame module was the only available microfiltration module. These units contained between 1 and 20 separate membrane envelopes sealed by gaskets. In most operations all the membrane envelopes were changed after each use the labor involved in disassembly and reassembly of the module was a significant drawback. Nonetheless these systems are still widely used to process small volumes of solution. A typical plate-and-frame filtration system is shown in Figure 7.10. 

Flat-sheet membranes are made in continuous rolls 500-5000 m long. Sheets of membrane 1-2 m long are cut and folded and then packaged as spiral-wound module envelopes. A single module may contain as many as thirty membrane envelopes. Currently, the industry standard spiral-wound module is 8 inches (1 inch = 2.54 cm) in diameter and about 35-40 inches long it contains 20-40 m2 of membrane. 

The plasma membrane envelops the cell, separating it from the external environment and maintaining the correct ionic composition and osmotic pressure... 

A remarkable effect of RO treatment was the appearance of swollen mitochondria with electron-transparent matrix and very few or no cristae. At low magnification these structures can easily be mistaken for vacuoles (Fig. 15.5a), but at higher magnification their two-membrane envelope is clearly visible (Fig. 15.5b). These bodies were identified as swollen mitochondria based on the fact that the cells containing them had no normal mitochondria while containing plastids much... 

Electron microscopy of radish radicle. Details of roots from seeds treated with 1/14-diluted reverse osmosis fraction, (a) Cortical cells showing protein-body-derived vacuoles (V) with remnants of electron-opaque protein material. Extremely swollen mitochondria (M) look like vacuoles with fine granular contents, (b) Detail of epidermal cell, showing swollen mitochondria (M), lipid droplets (L) and two dictyosomes (D). (c) The area enclosed in the rectangle in (b) is enlarged to show the two-membrane envelope and residual cristae (arrows) in a swollen mitochondrion. 

Electron microscopy of radish radicle. Details of columella cells from 16 h-control seed (a) and seed treated with 1/14-diluted reverse osmosis fraction (b-d). (a) Columella cells in the control are distinctly polarized and contain large amyloplasts (arrows). Nucleus (N). (b) Columella cells in treated roots are not polarized and contain no amyloplasts. The numerous electron-transparent vesicles are swollen mitochondria (M). (c) Detail showing swollen mitochondria (M) and starch-less plastids (P). (d) High magnification of swollen mitochondria showing the two-membrane envelope (arrows). 

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