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For example, the crown ether 18-crown-6 forms much stronger complexes with the potassium ion, K + than with the smaller sodium ion, Na +. [23] In hemoglobin an iron(II) ion is complexed by a macrocyclic porphyrin ring. The article hemoglobin incorrectly states that oxyhemoglogin contains iron(III).
The standard Gibbs free energy of formation (G f °) of a compound is the change of Gibbs free energy that accompanies the formation of 1 mole of a substance in its standard state from its constituent elements in their standard states (the most stable form of the element at 1 bar of pressure and the specified temperature, usually 298.15 K or 25 °C).
Calcium-binding proteins can be either intracellular and extracellular. Those that are intracellular can contain or lack a structural EF-hand domain. Extracellular calcium-binding proteins are classified into six groups. [2] Since Ca (2+) is an important second messenger, it can act as an activator or inhibitor in gene transcription.
Calmodulin is a small, highly conserved protein that is 148 amino acids long (16.7 kDa). The protein has two approximately symmetrical globular domains (the N- and C- domains) each containing a pair of EF hand motifs [5] separated by a flexible linker region for a total of four Ca 2+ binding sites, two in each globular domain. [6]
Being the conjugate base of a strong acid (nitric acid, pK a = -1.4), nitrate has modest Lewis basicity.Two coordination modes are common: unidentate and bidentate.Often, bidentate nitrate, denoted κ 2-NO 3, is bound unsymmetrically in the sense that one M-O distance is clearly bonding and the other is more weakly interacting. [2]
Ferric citrate or iron(III) citrate describes any of several complexes formed upon binding any of the several conjugate bases derived from citric acid with ferric ions. Most of these complexes are orange or red-brown. They contain two or more Fe(III) centers. [3] Ferric citrates contribute to the metabolism of iron by some organisms. Citrates ...
Thus, rise in extracellular Ca2+ ions may serve to prime the integrin heterodimer. The release of intracellular Ca2+ have been shown to be important for integrin inside-out activation. [16] However, extracellular Ca2+ binding may exert different effects depending on the type of integrin and the cation concentration. [17]
When calcium is added to or removed from the cytoplasm by transport across the cell membrane or sarcoplasmic reticulum, calcium buffers minimise the effect on changes in cytoplasmic free calcium concentration by binding calcium to or releasing calcium from intracellular proteins. As a result, 99% of the calcium added to the cytosol of a ...