Ion-binding ratio, kS (measure of buffering capacity)

Range kS[Ca2+]≈100: kS[Mg2+]≈20 unitless
Organism Unspecified
Reference OS. Andersen, "Cellular Electrolyte Metabolism", in Encyclopedia of metalloproteins, eds. Robert H Kretsinger Vladimir N Uversky E A Permi?a?kov, Springer 2013 pp.580-587 p.582 right column 4th paragraph
Primary Source Zhou Z, Neher E (1993) Mobile and immobile calcium buffers in bovine adrenal chromaffin cells. J Physiol 469: 245–273PubMed ID8271200
Comments "...This binding/buffering is even more pronounced in the intracellular compartment. For H+, the buffer capacity ß is defined as (Roos & Boron 1981) ß=?B/?pH, (eq.1) where B is the amount of strong base that is needed to produce a given change in pH. ߘ50mmole/(LXpH). The intracellular fluid is well buffered. In the case of Ca2+ (and Mg2+), the buffering is described using the ion-binding ratio, kS, defined as (primary source) kS=?(total [Ion2+])/?(free [Ion2+]) (eq.2) for Ca2+, kS˜100, for Mg2+, kS˜20. The low intracellular [Ca2+], [Ca2+]i, in particular means that Ca2+ becomes an important intracellular messenger because the transmembrane Ca2+ fluxes are large enough to cause measurable changes in [Ca2+]i."
Entered by Uri M
ID 110753