FIBER OPTIC SENSOR FOR CA2+ BASED ON AN INDUCED CHANGE IN THE CONFORMATION OF THE PROTEIN CALMODULIN

A fiber optic sensor that exploits the natural selectivity of the Ca2-binding protein calmodulin (CaM) is described. In this sensor, a dial ysis membrane is used to entrap a fluorescein-labeled CaM (F-CaM) solu tion at the common end of a bifurcated fiber optic bundle. Ca2+ ions i n a sample solution can diffuse through the membrane and bind to the F -CaM. Upon binding with Ca2+, CaM undergoes a conformational change th at induces a change in the fluorescence of the attached fluorescein ta g. 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 concentratio ns as high as 10(-2) M.