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Fiber optic sensor for Ca2+ based on an induced change in the conformation of the protein calmodulin
T L Blair1, S T Yang, T Smith-Palmer
1Department of Chemistry, University of Kentucky, Lexington 40506-0055.
Abstract:
A fiber optic sensor that exploits the natural selectivity of the Ca(2+)-binding protein calmodulin (CaM) is described. In this sensor, a dialysis membrane is used to entrap a fluorescein-labeled CaM (F-CaM) solution at the common end of a bifurcated fiber optic bundle. Ca2+ ions in a sample solution can diffuse through the membrane and bind to the F-CaM. Upon binding with Ca2+, CaM undergoes a conformational change that induces a change in the fluorescence of the attached fluorescein tag. This change in fluorescence can be related to the concentration of Ca2+ in the sample solution. The detection limit for the sensor is 5 x 10(-8) M Ca2+. The sensor has no interference by Mg2+ at concentrations as high as 10(-2) M.