Release from proteins

The absorption of sulfonylureas from the upper gastrointestinal tract is faidy rapid and complete. The agents are transported in the blood as protein-bound complexes. As they are released from protein-binding sites, the free (unbound) form becomes available for diffusion into tissues and to sites of action. Specific receptors are present on pancreatic islet P-ceU surfaces which bind sulfonylureas with high affinity. Binding of sulfonylureas to these receptors appears to be coupled to an ATP-sensitive channel to stimulate insulin secretion. These agents may also potentiate insulin-stimulated glucose transport in adipose tissue and skeletal muscle. 

During the normal synthesis and degradation of cellular proteins (protein turnover Chapter 27), some amino acids that are released from protein breakdown and are not needed for new protein synthesis undergo oxidative degradation. 

HPLC Separation of Selenoamino Acids Selenium proteins and amino acids have a wide variety of ionic characteristics that are pH dependent [149, 151, 152] and can be separated by anion, cation, and re versed-phase chromatography [94, 97, 98, 133, 135, 152-157]. Maher and his coworkers [30, 32, 37] used both anion and cation HPLC to confirm the identity of Se species (Figs 20.1 and 20.3). It should be noted that selenocysteine is released from proteins complexes with cysteine and chromatographs differently than the commercially available selenocystine [158]. Although the major selenoamino acid in mullet has been tentatively identified as selenocysteine (Fig. 20.3), further confirmation is required. 

To assess Se distribution and speciation in Brazil and other types of nuts, the defatted and powdered samples were fractionated into proteins and cytosol as shown by a Bow chart in Figure 21.1 [13, 14], For the evaluation of Se binding to proteins by SEC, protein precipitate was solubilized with SDS-containing acetate buffer. For the speciation of low-molecular-weight (LMW) Se compounds released from proteins, two procedures of protein hydrolysis were applied and the results obtained were compared. It was shown that acid hydrolysis with methane-sulfonic acid allowed for more efferent release of selenomethionine from proteins as compared with enzymatic proteolysis [14],... 

Koh JY, Suh SW, Gwag BJ, He YY, Hsu CY, Choi DW (1996) The role of zinc in selective neuronal death after transient global cerebral ischemia. Science 272 1013-1016 Koo EH, Squazzo SL (1994) Evidence that production and release of eimyloid beta-protein involves the endocytic pathway. J Biol Chem 269 17386-17389 Korichneva I, Hoyos B, Chua R, Levi E, HammerUng U (2002) Zinc release from protein kinase C as the common event during activation by lipid second messenger or reactive oxygen. J Biol Chem 277 44327 4331... 

The body contains many amino acids, some of which can be synthesized (non-essential amino acids), while others must be absorbed from the diet (the essential amino acids). Amino acids are the building blocks of protein, being attached together in groups to form the proteins that the body needs as part of its cellular structure or as enzymes, which are biological catalysts. Glutamate can be synthesized in the body, and it is also absorbed from food, in which it occurs as the free amino acid, or it can be released from proteins by digestion. 

Eacking wastes that are warm, high in BOD and yield a high level of icarbonate buffer as a result of ammonia release from protein breakdown. All of these conditions favor anaerobic processing. The use of this process scheme provides a high BSRT (15-30 days), usually required for anaerobic treatment, at a low HRT (1—2 days). 

The hydrophobically associated state represents the insolubility side of the T,-(solubility/insolubility)divide. As discussed in Chapter 5, contraction of the model elastic-contractile model proteins capable of inverse temperature transitions arises due to hydrophobic association. Hydrophobic association occurs, most fundamentally, on raising the temperature, on adding acid (H" ) to protonate and neutralize carboxylates (-COO ), and on adding calcium ion to bind to and neutralize carboxylates. Most dramatically, hydrophobic association occurs on dephosphorylation of (i.e., phosphate release from) protein, and it commonly occurs with formation of ion pairs or salt bridges between associated hydrophobic domains. 

Solid-phase chemistry After application of the sample to the slide, calcium is released from protein... 

Solid-phase chemistry Magnesium is released from protein, and penetrates the layers of the slide to react with a formazan dye. Calciiun is bound to a chelating agent to prevent interference. Accuracy was less satisfactory with control sera than with native sera. 

As all the methods mentioned above rely on the measurement of free iron after its release from proteins, iron released from hemoglobin would also be measured. For this reason any hemolysis will lead to falsely elevated plasma iron concentrations. 

As can be seen, the changes in AP were biphasic, namely, the initial transient decrease of AP induced by a hypothetical release of NO from low-molecular DNIC was replaced by long-term steady-state hypotension due to low rates of the NO release from protein-bound DNIC. The anisotropic shape of the 2.03 signal recorded in rat blood at ambient temperature provided additional evidence in feivor of formation of protein-bound DNIC in vascular tissue, while its continuance correlated with the duration of hypotension in DNIC-treated animals [83]. 

One of the greatest challenges in vitamin analysis is to extract them from the food matrix the problems are mainly due to their diflerent physieal and ehe-mical properties. Vitamins release from proteins is generally obtained by autoclaving the food sample (121 °C) or heating at 100 °C (AOAC 2006). 

Superoxide anion is produced by the addition of an electron to molecular oxygen. Superoxide anion can promote oxidative reactions by (1) reduction of transition metals to their more prooxidative state, (2) promotion of metal release from proteins, (3) through the pH dependent formation of its conjugated acid which can directly catalyze lipid oxidation, and (4) through its spontaneous dismu-tation into hydrogen peroxide. Due to the ability of superoxide anion to participate in oxidative reactions, the biological tissues from which foods originate will contain superoxide dismutase (SOD). 

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