Bicarbonate, incorporation into

The rate of C-bicarbonate incorporation into protein has also been used to estimate rates of phytoplankton N-assimilation (DiTuUio and Laws, 1983). This method, applicable to aU N-Umited marine ecosystems, builds on the observation that the C N ratio in protein is remarkably constant and that, under N limitation, a fairly constant percentage (85%) of phytoplankton N is incorporated into protein, with little or no N storage (DiTuUio and Laws, 1983). AppUcation of the method involves an incubation with " C-HCOa foUowed by extraction and isolation of the C-labeled protein fraction. From measurement of the ratio of the total... 

ITP can also act as a donor. This enzyme catalyses one of the rate limiting steps of gluconeogenesis. It may be assayed by u.v. spectroscopy using maiate dehydrogenase as an indicator of oxalacetate formation, or radiochemically using the same reactions and measuring C labelled bicarbonate incorporation into maiate [555]. 

Oxipurinol leads to an increase of bicarbonate- C incorporation due to an inhibition of the second part of pyrimidine biosynthesis as shown above. This is in keeping with the orotic aciduria after administration of oxipurinol observed in vivo. It is also in agreement with our results obtained in cultured human lymphoblasts (Banholzer et al. 1980, Banholzer et al. 1981). Purines did not reduce bicarbonate incorporation into orotic acid as they did in human cultured lymphoblasts. Conversely they increased... 

In addition to the formation of calcium carbonate sludge, some of the carbonate decomposes giving sodium hydroxide, which precipitates magnesium bicarbonate, and chloride, etc. as the hydroxide and is then incorporated into the carbonate sludge. Silicates are also often removed in the process as serpentine. Additional caustic may also need to be added, depending on the natural alkalinity present in the MU water. 

Various factors are required for regular fat digestion. Sublingual lipase and eventually a gastric lipase — which are both stable in an acidic environment — start digesting dietary fats in the stomach. In the intestine, pancreatic bicarbonate as well as bile acids are essential for emulsification of fats and fat-soluble substances which are then cleaved by pancreatic lipases. The cleavage products are incorporated into micelles and can then penetrate the unstirred water layer (UWL) which covers the intestinal surface. There, they can deliver the cleavage products of dietary fats as well as fat-soluble substances (e.g., carotenoids, vitamin E, vitamin A) to the luminal surface of the enterocytes. 

Fractionation and Contamination. The ratio 14C/12C in certain materials may be affected by isotopic fractionation. For example, the uptake of carbon dioxide and its incorporation into plant tissue may be accompanied by substantial fractionation that depends on the plant species. With marine organisms, fractionation may also be important, especially when inorganic carbonate and bicarbonate are involved. Corrections for fractionation must be made for precise radiocarbon dating. 

We already mentioned that the enzymes involved in the P-oxidation of fatty acids are located in the mitochondria. The source of two-carbon fragments for the biosynthesis of both fatty acids and isoprenoids like cholesterol is acetyl CoA, which is generated by oxidative metabolism in the mitochondria. Acetyl CoA cannot escape from the mitochondria, but it can be exported to the cyosol as citrate, where it is reconverted to oxaloacete and acetyl CoA. Fatty acid (and cholesterol) biosynthesis takes place in the cyosol, and requires bicarbonate, which is incorporated into acetyl CoA to form malonyl CoA by acetyl CoA carboxylase. The biosynthesis of fatty acids, mostly the Cie palmitate (Chapter 4), requires one molecule of acetyl CoA and seven molecules of malonyl CoA. In animals, the seven enzymatic reactions which are required for fatty acid synthesis are present in a single multifunctional protein complex, known as fatty acid synthase. The synthase also contains an acyl-carrier protein... 

The future of ISEs in the clinical chemistry instrumentation is quite exciting. As described in subsequent sections of this article, the coupling of enzyme and immunological reagents to ISE detectors to form bioelectrode systems appears to offer manufacturers a new approach toward the detection of metabolites such as creatinine and urea directly in blood and urine samples. Ultimately, such biosensors will be placed into complete electrode-based automated clinical analyzers. In addition, continued research on new membrane formulations, particularly liquid membrane ionophore systems, will result in the development of addition electrodes which can be incorporated into current analyzer systems to expand the electrolyte menu. Indeed, recent efforts have indicated that membranes selective fi)r bicarbonate (F5) and lithium (Z2) are likely additions in the near future. 

Figure 4 also shows the formation of carbonates from CO2 and a lattice oxygen. The nature of the surface sites involved in carbonate formation were not revealed in these studies. The results for [ 0] incorporation into the carbonate and bicarbonate species, following C 02 adsorption, suggest that these species are formed at different sites and that there is no direct conversion of the carbonate into the bicarbonate. 

Indirect evidence supporting this idea has been provided by the absence of 0 incorporation into bicarbonate when the CPS-catalyzed reaction is performed in 0-containing water demonstrates that... 

This degradation process is autocatalytic, since the g-hydroxybutyric acid that is produced catalyzes the hydrolysis reaction. To prevent abrupt degradation and erosion, a basic compound must be incorporated into the polymer. For example, sodium bicarbonate can be incorporated into a polymeric device composed of Alzamer to control the rate of polymer degradation and erosion. Although the polymer has been used for a number of drug delivery applications, it is difficult to produce and requires addition of significant amounts of a basic chemical to prevent uncontrolled degradation [21]. 

Claims have been made that the TBA does not enter into the product glassy phase.It has, however, also been reported that some TBA is indeed incorporated into the freeze-concentrate. If true, this might raise regulatory problems with pharmaceutical product registration. It is also not yet clear whether at temperatures in the region of Tg, the effect of TBA is unique. For instance, with sucrose-water systems, the presence of a volatile buffer salt (ammonium bicarbonate, acetate, formate) has a more marked effect on the sublimation rate than has TBA. On the other hand, with PVP-water systems, TBA is superior in enhancing the sublimation rate. It thus appears that the choice of excipient can also affect the drying rate. 

Wakil s pioneering studies on fatty acid synthesis included the crucial observation that bicarbonate is required for the synthesis of palmitoyl CoA. He was surprised to find that very low levels of bicarbonate could sustain palmitate synthesis that is, there was no correlation between the amount of bicarbonate required and the amount of palmitate produced. Later he also found that " C-labeled bicarbonate is not incorporated into palmitate. Explain these observations. 

---