Calcium ions biology

Absorption (A-max) 503 nm Emission (Amax) 536 nm Synthesis Synthetic methods Staining Applications Calcium ions Biological Applications tying ryanodine receptors modulators, taste receptors modulators ... 

Staining Applications Calcium ions Biological Applications Calcium indicator Industrial Applications Not reported Safety/Toxicity No data available... 

Discussion. This method is based upon the formation of a fluorescent chelate between calcium ions and calcein [fluorescein bis(methyliminodiacetic acid)] in alkaline solution.29 The procedure described below30 has been employed for the determination of calcium in biological materials.31 ... 

Calcium deposition biology, 6, 597 Calcium ions binding... 

Calcium activities as low as 5 x 10 7 M can be measured, with selectivity coefficients ACaMg and ACaK of 0.02 and 0.001, respectively. Such potential response is independent of the pH over the pH range from 5.5 to 11.0. Above pH 11, Ca(OH)+ is formed, while below pH 5.5, protons interfere. Because of its attractive response characteristics, the calcium ISE has proved to be a valuable tool for the determination of calcium ion activity in various biological fluids. 

Kessler, M., Hajek, K., Simon, W. Four-Barreled Microelectrode for the Measurement of Potassium, Sodium, and Calcium-Ion Activity, in Ion and Enzyme Electrodes in Biology and Medicine (Kessler, M., Clark, Jr, L. C., Lubbers, D, W., Silver, I. A., Simon, W., eds.) Munich Urban and Schwarzenberg, 1976, p. 136... 

The interest in colour indicators has recently increased as they are used for the direct determination of pH (acid-base indicators) and free calcium ions (fluorescent derivatives based on the calcium chelator EGTA as metallochromic indicators) in biological systems at cellular level. 

The natural fluorescence of CTC and its derivatives has been used extensively to determine small amounts of CTC in biological materials. Kohn (86) showed that the fluorescent complex formed by CTC with calcium ions and barbital could be extracted from animal tissues into an organic solvent and then measured spectrofluorometrically. The intense fluorescence of anhydro-CTC was used by Hayes and DuBuy (87) to determine CTC in animal tissues, tissue culture cells, and bacteria. Poiger and Schlatter (88) extracted CTC from biological material into ethyl acetate as the CTC-calcium trichloroacetate ion pair. The fluorescence of the antibiotic was then enhanced by the addition of magnesium ions and a base. 

In addition to 1-a-hydroxylase, the kidney also possesses a 24-hydroxylase which uses calcidiol as substrate the product of the reaction, 24,25 dihydroxy D3, is biologically inactive. This represents an important control point in the pathway. The activity of the 1-a-hydroxylase is promoted by calcium ions and the action of PTH acting via a G-protein/cAMP cascade. However, calcitriol itself simultaneously induces the 24-hydroxylase and suppresses 1-a-hydroxylase creating an effective feedback loop (Figure 8.12). 

Metals in biological systems function in a number of different ways. Group 1 and 2 metals operate as structural elements or in the maintenance of charge and osmotic balance (Table 1.2). Transition metal ions that exist in single oxidation states, such as zinc(II), function as structural elements in superoxide dismutase and zinc fingers, or, as an example from main group +2 ions, as triggers for protein activity—that is, calcium ions in calmodulin or troponin C... 

LIVER Use of isolated perfused liver in studies of biological transport processes, 192, 485 measurement of unidirectional calcium ion fluxes in liver, 192, 495 preparation and specific applications of isolated hepatocyte couplets, 192, 501 characterizing mechanisms of hepatic bile acid transport utilizing isolated membrane vesicles, 192, 517 preparation of basolateral (sinusoidal) and canalicular plasma membrane vesicles for the study of hepatic transport processes, 192, 534. 

System 22 is an earlier example which incorporates Tsien s selective calcium receptor 23. ° System 23 has also been employed for the construction of ratiometric fluorescent sensors involving wavelength shifts. System 22 and other related PET sensors provide some of the most visually dramatic fluorescence off-on switching induced by biologically relevant levels of calcium ions in addition to their consistent predictability of most sensor parameters. 

Calcium ions entering cells from the outside or released from internal stores trigger many biological responses (see Box 6-D). Within cells Ca2+ often accumulates in mitochondria, in the ER, or in vesicles called calciosomes.265 Release of the stored Ca2+ is induced by hormones or by nerve impulses. For example, impulses flow from the nerve endings into the muscle fibers and along the invaginations of the plasma membrane called transverse tubules (Chapter 19). There they induce release of Ca2+ from the ER. The released ions activate enzymes266 and induce contraction of the muscle fibers. In many cells, Ca2+ causes release of secreted materials, for example, neurotransmitters in the brain 267/268... 

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