Measuring the Rate Constants of Ca2+ Indicators

Abstract

Fluorescent Ca2+ indicators are widely used to measure the concentration of free Ca2+ ([Ca2+]free) in biological processes. To determine the exact kinetics of changes in [Ca2+]free and the processes underlying these changes (e.g., Ca2+ binding to Ca2+-binding proteins), it is necessary to know the exact binding properties of the indicator used. Here, we describe how to determine the binding rate constants (kon and koff) of Ca2+ indicators.