Glucose trapping

If we wish to devise a chemical version of the biosynthesis of inositols, we need to use cleverly devised protecting groups to make sure that the right OH group is oxidized to a ketone. We can start with glucose trapped in its furanose form by a double acetone acetal as we discussed above. The one remaining OH group is first blocked as a benzyl ether. 

Glucose enters cells by carrier-mediated diffusion. Once inside the cell, it is phosphorylated to glucose 6-phosphate, a reaction catalysed by the enzyme hexokinase, using ATP as the phosphate donor (section 5.4.1 and Problem 2.1). Glucose 6-phosphate does not cross cell membranes, and therefore there is a net accumulation of [glucose plus glucose 6-phosphate] inside the cell, at the expense of 1 mol of ATP utilized per mole of glucose trapped in this way. Vitamins (riboflavin section 11.7.1) and Bg (section 11.9.1) are similarly accumulated inside cells by phosphorylation at the expense of ATE... 

In addition to mixtures of single-chained anionic and cationic surfactants, mixtures of single-chained anionic surfactants with double-chained cationic surfactants have also been studied. The phase equilibria of the SDS-DDAB-water system have been studied by water deuteron nuclear magnetic resonance (NMR) and polarization microscopy methods at 40°C [27]. Based on particle size measurements, the possibility of vesicle formation has been realized from this study. Spontaneous vesicle formation in the aqueous mixture of didodecyldimethylammonium bromide and sodium dodecyl sulfate has been investigated with differential interference microscopy, transmission electron microscopy, glucose-trapping experiments, -potential measurements, and surface-tension measurements [28]. A solution of DDAB with a small amotmt of SDS is a lamellar phase. Adding more SDS induces surfactant precipitation. Further addition of SDS causes DDAB-SDS precipitate to disperse and results in the vesicle formation. The DDAB and SDS mixtures yield... 

The amount of glucose trapped in DDAB-SDS (or -SDeS) decreased with an increase of the anionic surfactant. However, at the lowest anionic surfactant mole fraction that forms spontaneous vesicle when mixed with DDAB, much more glucose was trapped than trapped by vesicles formed with only DDAB. For example, a mixture with an SDS mole fraction of 0.64 trapped 2.2 L/mol compared to 0.9 L/mol trapped by DDAB alone. 

The membrane of an erythrocyte comprises intricately linked lipid and protein components. Therefore, liposomes made without structural proteins cannot be fully satisfactory model systems. Nevertheless, a-terthienyl induced photodynamic membrane damage in glucose-containing liposomes, probably through lipid peroxidation 185). The modification of the membrane properties was revealed by leakage of glucose trapped in the liposomes. 

The action of this enzyme on glucose traps it in the cell as the product of the reaction cannot cross the cell membrane... 

Retention, too, is highly tissue-specific. Sometimes, the extraction mechanism is also the retention mechanism, as for Tc-sestamibi, which is retained in mitochondria as long as transmembrane potentials remain intact. Others are separate. F-2-Fluorodeoxyglucose enters the cell by the same pathway as glucose, but is trapped because it is not a substrate for hexokinase, preventing further intracellular metabohsm. 

With regard to biosensor applications, a wide variety of electrochemically active species (ferrocene, ruthenium complexes, or carbon and metal (Pt, Pd, Au...) [185,186] were also introduced into the sol-gel matrices or adsorbed to improve the electron transfer from the biomolecules to the conductive support [187,188]. For instance, glucose oxidase has been trapped in organically modified sol-gel chitosan composite with adsorbed ferrocene to construct a low-cost biosensor exhibiting high sensitivity and good stability [189]. 

Hexokinase/glucokinase glucose entering the cell is trapped by phosphorylation using ATP. Hexokinase is widely distributed in tissues, whereas glucoldnase is found only in hepatocytes and pancreatic 3-islet cells. Table I-I2-2 identifies the differences in their... 

Once transported into tissues, galactose is phosphorylated (galactokinase), trapping it in the cell. Galactose 1-phosphate is converted to glucose 1-phosphate by galactose 1-P uridyltrans-ferase and an epimerase. The pathway is shown in Figure 1-12-5 important enzymes to remember are ... 

Shake flasks were inoculated with mixed liquor suspended solids from activated sludge units in a Houston area domestic waste sewage treatment plant. Initial surfactant concentrations were 20 mg/ . CO2 formed from biodegradation was trapped in aqueous Ba(OH)2. The amount of CO2 formed was determined by back-titrating residual Ba(OH)2 with HCl at the end of each test period. Glucose was included as a positive biodegradation standard. 

The amount of total enzymatic activity that becomes manifest only after disruption of membranous barriers between enzyme and substrate or upon removal of some otherwise inhibitory factor. Membrane disruption is often achieved by treatment with detergent to solubihze the enzyme. One example is the so-called microsomal glucose-6-phosphatase, an enzymatic activity that is located in the lumen of the endoplasmic reticulum but becomes trapped as a latent activity in microsome vesicles upon mechanical disruption of cells. 

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