Calcium Sensing

Understanding a Calcium Sensing System


Calcium is one of the most important ions in physiology wherein fluctuations in Ca2+ levels impact muscle contraction, blood clotting, and neurotransmission. These responses are mediated by calcium ion binding to calcium sensing proteins. Calcium binding induces protein conformational changes enabling intermolecular interactions. In this study we utilize surface plasmon resonance (SPR) to determine the affinity of a calcium sensing protein for a protein binding partner. In a separate study, we titer Ca2+ into the apo form of the protein to determine the concentration of calcium ion required to promote the protein-protein interaction.

Materials and Methods

The samples used in this study were blinded at the request of the customer.


The calcium binding protein (CaBP) was injected from 100 nM to 100 μM across a sensor chip in which the protein binding partner had been immobilized. A concentration of calcium was used that saturated the injected calcium binding protein.

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