Mitochondrial Photobiomodulation
The mechanism sits inside the mitochondrion. 660nm photons hit the heme a3 center; 830–860nm hit the copper centers — both of Complex IV, the last enzyme in the electron transport chain. Karu 2010 mapped the pathway: photons dissociate inhibitory nitric oxide, electrons flow, ATP returns. Every downstream effect — procollagen, vasodilation, anti-inflammatory — starts here.
About this topic
Mitochondrial photobiomodulation describes the direct photochemical interaction between red and near-infrared photons and the mitochondrial electron transport chain. The primary chromophore is cytochrome c oxidase (Complex IV), a metalloenzyme containing copper centers that absorb photons at 660nm (heme a3 center) and 830–860nm (CuA and CuB centers). Photon absorption causes photodissociation of inhibitory nitric oxide from the binuclear center of Complex IV, immediately restoring electron transport and ATP synthesis. Karu (2010, PMID 20374017) established the complete mechanistic pathway. Downstream effects include: increased ATP availability for collagen synthesis, release of free nitric oxide promoting vasodilation, modulation of reactive oxygen species triggering adaptive hormetic responses, and activation of transcription factors (NF-kappaB, AP-1) regulating cell proliferation and survival.