Figure 1

Photoreduction of coenzyme Q (CoQ₁₀) activates complex III, which reduces cytochrome c, resulting in generation of ATP, in animal mitochondria.

(A) Schematic of pheophorbide-a (PA) catalyzed photoreduction of coenzyme Q (also known as ubiquinone/ubiquinol). (B) Photoreduction of ubiquinone in liposomes catalyzed by PA. The x-axis represents the amount of time the liposome mixture was exposed to red light. (C) Photoreduction of ubiquinone in isolated, intact heart mitochondria. Mitochondria were either treated with PA (+) or not treated with PA (−). When exposed to light, 86% of CoQ₁₀ was reduced to ubiquinol in PA treated mitochondria (red line) but not for control mitochondria (blue line). When the light was turned off, ubiquinol was reoxidized. (D) Photoreduction of ubiquinone activates complex III resulting in the reduction of cytochrome C. Reaction conditions noted on the x-axis. Values represent the amount of cytochrome c reduced upon exposure to light minus the amount of cytochrome c reduced when the same samples were kept in the dark. Averages of 8 replicates and standard deviations are shown. CytC: cytochrome c; Mito: mitochondria; *P-value < 0.05 determined by unpaired Student’s t-test. (E) Storage of photonic energy by animal mitochondria. ATP synthesis in the PA treated (+) and control (−) mitochondria exposed to red light as measured by the luciferase assay. ATP synthesis was coupled to CoQ₁₀ photoreduction. (F) ATP concentrations and ATP/AMP and ATP/ADP ratios, as measured by UPLC in the light exposed, PA treated heart mitochondria (+, red lines), were consistent with ATP synthesis from ADP and AMP pools. PA-naïve, light exposed mitochondria (−, blue lines) showed no change in adenosine nucleotides.