Membrane encapsulation

In apoptotic cell death, several factors such as growth factors, NO, the tumor suppressor gene p53, and the protein encoded by this gene contribute to the process that leads to cell death. One of the functions of p53 protein is the activation of apoptosis if a cell is transformed to a malignant cell. Apoptosis typically leads to the formation of smaller membrane-encapsulated particles within the cell. Apoptotic cell death begins in the nucleus and proceeds to other parts of the cell. The death process may be quite advanced before it can... 

Sol-gel-derived membranes encapsulating a bis(crown ether) derivative [bis(12-crown-4-ylmethyl) 2-dodecyl-2-methylmalonate] [28] were also fabricated with an initial DEDMS/TEOS ratio of 3 for Na -ISFETs. The Na -ISFETs showed a Nernstian response to Na+ activity changes in the activity range of 1 x 10 " to 1 M and a short response time of 2 s. Employment of a polythiophene interlayer improved the potential instability and the lower detection limit in both of the K - and Na -ISFETs based on the sol-gel-derived membranes with the initial DEDMS/TEOS ratio of 3 (Fig. 8). 

Selectivity coefficients values for K - and Na -ISFETs with the optimized ion-sen-sing membranes encapsulating valinomycin and bis(12-crown-4) are summarized in Fig. 9. The selectivity coefficient for with respect to Na in the K -ISFET is 2 x 10 " and that for Na with respect to in the Na -ISFET is 3 x 10. The selectivity coefficient values are similar to those for the ISFETs and ion-selective electrodes with the previous membrane materials containing the same neutral carriers. The high sensitivity and selectivity for the neutral-carrier-type ISFETs based on sol-gel-derived membranes can last for at least 3 weeks. 

FIG. 10 SEM photographs for sol-gel-derived (a) and plasticized-PVC (b) membranes encapsulating bis(12-crown-4) after protein adsorption test. (From Ref 27.)... 

Appropriate fabrication of sol-gel-derived membranes encapsulating neutral carriers such as valinomycin can afford an excellent type of neutral-carrier-type ion-sensing membranes for ISFETs [27] as already mentioned. The simple encapsulation of neutral carriers in sol-gel-derived membranes, however, has a drawback the encapsulated neutral carriers are still apt to exude from the membranes into aqueous sample solutions, which thereby makes the resulting ion sensors less durable and more toxic. Incorporation of neutral carriers to sol-gel-derived membranes by covalent bonding is desirable. 

Quaternary alkylammonium salts are generally water-soluble surfactants. The sol-gel-derived anion-sensing membranes encapsulating a quaternary alkylammonium salt, especially with high contents, are easy to deteriorate due to the exudation of the cationic site from the membrane to aqueous sample phases. Moreover, another issue concerning the dispersibility of ammonium salts in sol-gel-derived membranes may happen when high... 

FIG. 15 Potential response of anion ISFETs based on sol-gel-derived membranes encapsulating trioctylmethylammonium chloride ( ) and modified chemically by alkoxysilylated quaternary ammonium salt (12) (O) to CC-activity changes. (From Ref 50.)... 

Fig. 10 (a) Chemical structure of PEG-6-PCL copolymer, (b) CLSM image of PEG-6-PCL polymersomes containing membrane-encapsulated Nile Red (2 mol%) and aqueous entrapped Calcein dyes. Scale bar 5 pm. (c) Cryo-TEM image of PEG-6-PCL polymersomes. Scale bar 100 nm. Reprinted from [228] with permission... 

Binding is followed by invagination of the membrane to surround the entire particle and the membrane-encapsulated particle pinches off from the plasma membrane to form a phagosome. 

How the various components of the lipoproteins are assembled and secreted into the plasma is not known. Current ideas for this process suggest the assembly of VLDL from its components occurs in the endoplasmic reticulum, VLDL is transferred to the Golgi apparatus and is subsequently secreted via secretory (membrane-encapsulated) vesicles. These vesicles fuse with the plasma membrane and release their lipoprotein contents into plasma (fig. 20.14). 

Cells are broadly classified as either prokaryotes or eukaryotes. Prokaryotic cells are found in simpler organisms, such as bacteria. They do not have a membrane enclosed nucleus, but their DNA is dispersed in the cytoplasm of the cell. Eukaryotic cells are found in all members of the animal kingdom. Their structures contain distinct membrane encapsulated compartments, such as the nucleus, which contains their DNA, mitochondria and lysomes. These separate compartments are known as organelles. 

As shown in Figure 6.7, the concentration gradient in the membrane reaches a constant pattern over time (theoretically infinite time). A membrane-encapsulated sphere containing a saturated drug concentration (constant activity, Cs), has a constant rate of drug diffusion. In this case, Equation (6.33) becomes ... 

Mohan, R. R. Li, N. N. "Reduction and Separation of Nitrate and Nitrite by Liquid Membrane-Encapsulated Enzymes" Biotech, and Bioeng. 1974,16, pp 513-523. 

Miyako, E., Maruyama, T., Kubota, P., Kamiya, N., Goto, M. (2005). Optical resolution of various amino acids using a supported liquid membrane encapsulating a surfactant-protease complex. Langmuir, 21, 4674-79. 

Medical devices, surgical membranes Encapsulation of electronic parts Caulking, sealing compounds Cosmetics, pharmaceuticals... 

The concept of zeolite membrane encapsulated catalyst (ZMEC) is an original way to use zeolite membranes in catalytic reactors [158,159]. The concept of coating catalyst particles with a selective zeolite layer can reveal useful for either increasing reactant selectivity (e.g. selective hydrogenation of linear molecules) or product selectivity (e.g. animation of methanol). It also protects the catalyst from poisoning. 

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