Ions, in cells

Shimomura, O., and Johnson, F. H. (1979a). Chemistry of the calcium-sensitive photoprotein aequorin. In Ashley, C. C., and Campbell, A. K. (eds.), Detection and Measurement of Free Calcium Ions in Cells, pp. 73-83. Elsevier/North-Holland, Amsterdam. 

The mobility of lithium ions in cells based on cation intercalation reactions in clearly a crucial factor in terms of fast and/or deep discharge, energy density, and cycle number. This is especially true for polymer electrolytes. There are numerous techniques available to measure transport... 

Potassium, along with nitrogen and phosphorus, is an essential element needed for plant growth. In plants, it occurs mostly as K+ ion in cell juice. It is found in fruit or seed. Deficiency can cause curling leaves, yellow or brown coloration of leaves, weak stalk and diminished root growth. Potassium deficiency has been associated with several common animal ailments. Potassium is in extracellular fluid in animals at lower concentrations than sodium. 

The major in situ process that results in the formation of H202 is undoubtedly photochemical (e.g., 12, 15, 49, 50). Photochemical formation of H202 in fresh and salt waters probably results from the disproportionation of the superoxide ion radical, 02 (8, 9, 15, 51, 52). The kinetics of superoxide disproportionation are well established (53), and its steady-state concentration can be calculated. Because of the known effects of superoxide ion in cells (47), its presence in surface waters may be important in biologically mediated processes. However, other sources, such as biological formation (e.g., 45, 54), redox chemistry (21, 24, 29, 31, 32), wet (e.g., 55) and dry (50, 56, 57) deposition, and surfaces (e.g., 58) may also be important. 

DJ Hook, LT Chang, RP Elander, RB Morin. Stimulation of the conversion of penicillin N to cephalosporins by ascorbic acid, a-ketoglutarate and ferrous ions in cell-free extracts of strains of Cephalosporium acremonium. Biochem Biophys Res Commun 87 258-265, 1979. 

Immediately after switching-on a constant current both ions and electrons do flow according to their transference numbers while the voltage increases from zero to IRx (or more precisely to I(RX + R )). With increasing time the partial current of the blocked species decreases, and eventually vanishes leading to a steady state in which the total current is carried only by the nonblocked species, i.e., the electrons in cells 3 and 4 or the ions in cells 5 and 6. Hence the steady state reveals the conductivity of the nonblocked species. The comparison with the total conductivity (e.g., obtained from the IR-drop at the beginning of the experiment) also yields the conductivity of the blocked species. 

In most electrochemical measurements solutions are made up to an arbitrary volume that usually is at least 1 cm3. However a few microcells have been described for work with solution volumes that are well below 1 cm3. The coulometric determination of silver ion in cell volumes as small as 20 /iL (formed by a thin copper sheet and a cavity of beeswax) has been discussed.62... 

Jelicks, L.A. Gupta, R.K. (1989). Double-quantum NMR of sodium ions in cells and tissues. Paramagnetic quenching of extracellular coherence. J. Magn. Reson. 81,586-592. 

It is essential to maintain the balance between Na+ and K+ ions in cells and surrounding fluids. Discuss. 

Membranes are structurally and functionally asymmetric. The outer and inner surfaces of all known biological membranes have different components and different enzymatic activities. A clear-cut example is the pump that regulates the concentration of Na+ and K+ ions in cells (Figure 12.34). This transport protein is located in the plasma membrane of nearly all cells in higher organisms. The Na+-K+ pump is oriented so that it pumps Na+ out of the cell and K+ into it. Furthermore, ATP must be on the inside of the cell to drive the pump. Ouabain, a specific inhibitor of the pump, is effective only if it is located outside. 

Takeichi, M. and Okada, T. S. (1972). Roles of magnesium and calcium ions in cell-to-substrate adhesion. Exp. Cell Res. 74, 51-60. 

Plants could maintain the necessary concentrations of essential metal ions in cells by homeostatic mechanisms. They are also involved in the reduction of damage induced by heavy metal toxicity. One of the major tolerance mechanisms is chelation of heavy metals by a family of peptide ligands, the phytochelatins (similar to other xenobiotics) [108], The molecular basis for the chelators and chaperone synthesis is well known and could be applied in the modification of tolerant plants. Tolerance to Cd and As is largely dependent on the phytochelatin pathway, but molecular biology of Cd hypertolerance in certain plant species, such as the... 

Lehrman, Sally. Sobering Shift. Scientific American 290 (April 2004) 22. This article describes how a particular gene controls a gateway for the flow of potassium ions in cells, which could determine sensitivity to alcohol as well as provide a mechanism for intoxication. 

N,N -di[ll-(ethoxycarbonyl) undecul]-N,N -4,5-tetramethyl-3,6-dioxaoctan-l,8-diam-ide). (B) Schematic arrangement for the measurement of the activity (or concentration) of Ca " ions in cells using a Ca -selective double-barreled microelectrode. Frequently the microelectrode is supplemented by a third, indifferent, electrode inserted into the bathing medium surrounding the cell. ... 

Figure lb displays examples of pH oscillations observed in Cell II, with glucose level and pH fixed in Cell I. Oscillations persist for about one week, and period increases steadily with time. This drift, along with the ultimate cessation of oscillations, is believed to follow from the slow buildup of gluconate ion in Cell II (see below), which acts as a buffering species (77,72). In the present work, we shall ignore these aspects, which are not relevant to the capacity of the system to initiate oscillations. A more comprehensive analysis of the system is needed to account for these phenomena. 

Step 2 When a sufficient number of carboxylates have been neutralized, the membrane responds by switching to its collapsed, low permeability state. Consequently, glucose flux into Cell II and hydrogen ion production are attenuated, and pHu levels off. Hydrogen ions in Cell II, in addition to diffusing into the membrane, are removed, in the presence of marble (CaC03), by a sequence of acid-base reactions (16) ... 

Based on these assumptions, the following differential equations govern the hydrogel membrane thickness (Z), the flux of hydrogen ions into the membrane, which then become either free intramembrane hydrogen ions () or protons bound to pendant carboxyls (), and the concentration of free hydrogen ions in Cell II (C ) ... 

Hook, D. J., L. T. Chang, R. P. Elander, and R. B. Morin Stimulation of the Conversion of Penicillin N to Cephalosporin by Ascorbic Acid, a-Ketoglutarate, and Ferrous Ions in Cell-Free Extracts of Strains of Cephalosporium acremonium. Biochem. Biophys. Res. Commun. 87, 258 (1979). 

The mechanisms by which stable bonds to these anodized surfaces are achieved have been extensively studied. " In the BAC 5555 process, a whiskered porous oxide structure less than 1 p,m thick is developed over a thin barrier layer. The incorporation of phosphate ions in cell walls inhibits oxide hydration and condibutes to greater bond durability. 

In order for the bilayers to function in cell medium at 37 °C, and in order for them to occupy minimum real estate on the surface of the chip so that the maximum number of devices can be realized per unit area, it was necessary to carry out considerable basie characterization. For example, at body temperature the bending angle is different from that at room temperature [35], so the length of the bUayer hinges had to be adjusted. The design also had to consider the mixture of ions in cell medium the polymer has a different affinity for different ions, and they travel within the polymer at different speeds [36], affecting the strain. 

Comparison of these results to vanadyl complexes formed in vivo vide infra) demonstrated that eomplexes assigned as VO-GSH compounds in the cytosol (pH 7.4) [63,64] or detected in the liver and kidney by EPR and ESEEM [54,69,71,72] would only be consistent with structures detected in these studies at pH < 6.5. Other potential bioligands would therefore have to be considered to describe the in-vivo coordination of vanadyl ions in cells and organs. These studies serve to highlight the crucial role played by EPR in the delineation of possible physiologically relevant structures in a system with no available x-ray structural data [48]. 

The concentration of pyrophosphate ion in cells is very low, and the conversion of alcohols to pyrophosphates does not occur by itself. So, how are alcohols converted to pyrophosphates in cells The answer is that the source of pyrophosphate is not the pyrophosphate ion or phosphoric acid, but adenosine 5 -triphosphate (ATP), which contains a pyrophosphoryl group. 

The resulting enzyme has a high affinity for K+ and a low affinity for Na+. Hydrolysis of the phosphorylated enzyme results in the liberation of inorganic phosphate and the regeneration of the enzyme form with high affinity for Na+ and low affinity for K+. The net result is the movement of two K+ ions into the cell and three Na+ ions out of the cell for each ATP hydrolyzed. About 25% of the energy consumption of a human at rest is used to maintain the resting concentration of sodium and potassium ions in cells. 

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