Dynamic calculation of ATP/O ratios measured using Magnesium Green (MgGr)™

Mitochondria generate aerobic cellular energy (i.e., ATP) through the reduction of oxygen to water via oxidative phosphorylation. The efficiency of this pathway can be measured by the phosphate/oxygen (ATP/O) ratio, which is the amount of ATP produced per oxygen atom reduced. This ratio thus provides a measure of the efficiency of mitochondrial respiration that can be readily compared between species. The magnesium green (MgGr) fluorometric method permits easy measurement of ATP/O ratios from isolated mitochondria but the standard analysis approach employs an endpoint method to calculate ATP/O ratios. Here, we present a modified method of ATP/O calculation that permits dynamic observation of fluorescent measurements of the consumption of O(2) (JO(2)) and the production of ATP (JATP). Specifically, by substituting the slope of a straight line within a given period of time (seconds to minutes) with the slope of a tangent to each time point (per second), it is possible to evaluate JO(2), JATP and the ATP/O ratio in a dynamic manner. • Provides second-by-second visualization of ATP/O ratios throughout experiments vs. a single measurement. • Dynamic visualization allows for easy identification of outlying data and more accurate calculation of mean ATP/O ratios.