Minimizing ATP depletion by oxygen scavengers for single-molecule fluorescence imaging in live cells.

The stability of organic dyes against photobleaching is critical in single-molecule tracking and localization microscopy. Since oxygen accelerates photobleaching of most organic dyes, glucose oxidase is commonly used to slow dye photobleaching by depleting oxygen. As demonstrated here, pyranose-2-oxidase slows bleaching of Alexa647 dye by ∼20-fold. However, oxygen deprivation may pose severe problems for live cells by reducing mitochondrial oxidative phosphorylation and ATP production. We formulate a method to sustain intracellular ATP levels in the presence of oxygen scavengers. Supplementation with metabolic intermediates including glyceraldehyde, glutamine, and α-ketoisocaproate maintained the intracellular ATP level for at least 10 min by balancing between FADH2 and NADH despite reduced oxygen levels. Furthermore, those metabolites supported ATP-dependent synthesis of phosphatidylinositol 4,5-bisphosphate and internalization of PAR2 receptors. Our method is potentially relevant to other circumstances that involve acute drops of oxygen levels, such as ischemic damage in the brain or heart or tissues for transplantation.