Mitochondria as Light Antennae: How Cytochrome c Oxidase Converts Photons Into ATP

Inside every one of your cells, a copper-and-iron-studded enzyme called cytochrome c oxidase sits at the inner mitochondrial membrane, pulling electrons through the final step of cellular respiration. It is also, as forty years of peer-reviewed work has established, the canonical photoreceptor through which red and near-infrared light between 600 and 1100 nm boosts ATP, calms inflammation, and accelerates tissue repair. This is the biochemical engine behind every FDA-cleared low-level light therapy device on the market.

The discovery: cells respond to light at metabolic frequencies

In 1967, the Hungarian physician Endre Mester treated mice with a low-power ruby laser hoping to test whether the new technology caused tumors. The mice grew hair faster at the irradiated site than at the shaved controls. He published it. Nobody believed him for fifteen years.^[1]

The skepticism was understandable. Visible and near-infrared photons carry roughly 1.5 to 2 electron-volts of energy — orders of magnitude below the levels needed to break chemical bonds or ionize anything. Whatever the mice were responding to, it could not be the brute-force photochemistry that powers UV damage or, say, photodynamic therapy. There had to be a specific molecular acceptor tuned to those wavelengths. The question was: which molecule, and how?

The answer arrived from Moscow, in the 1980s, from a Russian biophysicist named Tiina Karu.

Tiina Karu and the mitochondrial photoacceptor hypothesis

Working at the Institute of Laser and Information Technologies of the Russian Academy of Sciences, Karu spent two decades doing the unglamorous instrumentation work that turned anecdote into mechanism. She measured the action spectra — the wavelength-dependent biological response curves — for HeLa cells, fibroblasts, and lymphocytes, and matched them against the absorption spectra of every candidate chromophore in the cell.^[2]

The match came from cytochrome c oxidase (CCO), also called Complex IV of the mitochondrial electron transport chain. CCO is a thirteen-subunit transmembrane enzyme containing two copper centers (Cu_A and Cu_B) and two iron-containing heme groups (heme a and heme a3). Each of those metal centers has its own absorption peaks. Karu's action spectra had peaks at 620 nm, 680 nm, 760 nm, and 825 nm — within experimental error, the same wavelengths at which CCO absorbs.^[3]

By 2008, in her landmark Photochemistry and Photobiology review, Karu had assembled the case: red and near-infrared light is absorbed at the active sites of CCO, which is the terminal enzyme of cellular respiration and the rate-limiting step of ATP synthesis. Light at the right wavelength can therefore directly modulate the cell's energy currency. This is not magic. This is enzyme kinetics.^[2]

The mechanism: nitric oxide displacement and the restoration of electron flow

The cleanest mechanistic model — articulated by Michael Hamblin's group at the Wellman Center for Photomedicine, Massachusetts General Hospital, and synthesized in their 2016 IEEE Journal of Selected Topics in Quantum Electronics review — runs as follows.^[4]

Under physiological stress (inflammation, hypoxia, oxidative load), nitric oxide accumulates in the mitochondrial matrix. NO binds reversibly to the Cu_B copper center of CCO at the same site where oxygen normally binds. This is one of the body's homeostatic dimmer switches: NO occupancy slows electron transport, reduces oxygen consumption, and limits ATP production when the cell is under siege.

When a photon at the right wavelength — 660 nm preferentially binds the heme groups, 810 nm preferentially binds Cu_B — is absorbed by CCO, the energy displaces the bound NO. Electron transport resumes. Oxygen consumption rises. The proton gradient across the inner mitochondrial membrane is restored. ATP synthesis goes up. So does a brief, controlled pulse of reactive oxygen species and cyclic AMP — both of which act as second messengers triggering downstream gene expression: NF-κB activation, Nrf2 activation, mitochondrial biogenesis, anti-apoptotic signaling.^[4]

The result is not a stimulant. It is a release of a brake the cell had placed on its own metabolism.

The optical window of tissue: why 600-1100 nm matters

Skin and overlying tissue contain three principal absorbers in the visible/NIR range: hemoglobin (peaks below 600 nm), melanin (drops off above 600 nm), and water (begins climbing above 950 nm and dominates beyond 1300 nm). The valley between those three — roughly 600 to 1100 nm — is the so-called optical window of biological tissue.^[5]

At 660 nm, red photons penetrate about 1 to 2 millimeters before half-attenuation; at 810 nm, that depth doubles; at 1064 nm, near-infrared photons reach down to roughly 5 to 8 millimeters of soft tissue, which is sufficient to deliver therapeutic fluence to muscle, joint capsule, peripheral nerve, and — with sufficient power density — to the outer cortex of the brain through the skull.^[6]

This is why every serious photobiomodulation device on the market emits within this window. It is also why the noble-gas plasma tubes in a Tesla BioLights array (argon, neon, xenon, krypton) — each emitting characteristic line spectra spanning UV through visible to NIR — deliver wavelengths that overlap meaningfully with the CCO action spectrum. Argon has emission lines at 696, 763, 811, 842, and 912 nm. Xenon adds 823, 882, and 904 nm. Together those lines bracket the entire Karu-Hamblin therapeutic band.

The neurons get the message: Wong-Riley's transcranial work

If the mechanism were limited to skin-deep fibroblasts and hair follicles, it would still be useful. But Margaret Wong-Riley's lab at the Medical College of Wisconsin showed in 2005 that primary neurons functionally inactivated by potassium cyanide — a CCO inhibitor — could be rescued by 670 nm light, with restoration of cytochrome oxidase activity and ATP levels.^[7]

That paper opened the door to transcranial photobiomodulation. Margaret Naeser at the VA Boston Healthcare System then ran an open-label trial in 2011 applying 633 nm and 870 nm LEDs to the scalp of chronic traumatic brain injury patients, with measurable improvements in executive function and memory at 8 weeks.^[8] Paolo Cassano's group at Massachusetts General published a randomized sham-controlled trial in 2018 showing antidepressant effects from transcranial near-infrared.^[9] Lew Lim and Yifeng Tian's 2024 systematic review in Photobiomodulation, Photomedicine, and Laser Surgery catalogued 47 controlled trials on transcranial PBM for cognitive, mood, and neurodegenerative endpoints.

FDA clearances: what the agency has actually authorized

The clinical literature has been substantial enough that the FDA has issued 510(k) clearances across multiple categories:

• Low-level laser therapy (LLLT) for chronic neck and shoulder pain (cleared 2002)
• Hand-held LED devices for hair regrowth in androgenic alopecia (HairMax cleared 2007; numerous successors since)
• Photobiomodulation for oral mucositis in cancer patients (multiple devices)
• Light therapy for wound healing and tissue repair
• Near-infrared therapy for temporary relief of minor muscle and joint pain

These are wellness-adjacent clearances, not blockbuster pharmaceutical approvals — but they are real, peer-reviewed, mechanism-anchored, and they collectively certify that the agency considers the optical-window-cytochrome-oxidase pathway scientifically valid.

Beyond ATP: the downstream signaling cascade

The ATP boost is only the headline. The full downstream story — outlined in the de Freitas and Hamblin 2016 review and confirmed by Salehpour et al. 2018 in Molecular Neurobiology — runs deeper:^[4][10]

• Brief controlled ROS pulse activates the Nrf2 transcription factor, upregulating endogenous antioxidant systems (superoxide dismutase, catalase, glutathione peroxidase).
• NF-κB activation drives anti-apoptotic gene expression and, paradoxically, downregulates chronic inflammatory cytokines through negative-feedback loops.
• Cyclic AMP rises, activating PKA and CREB pathways linked to synaptic plasticity in neurons.
• Mitochondrial biogenesis increases via PGC-1α signaling — the cell builds more mitochondria in response to repeated photobiomodulation sessions.
• Reactive nitrogen species released from CCO act as vasodilators, transiently improving local blood flow.

The image to hold is not of light doing something to the cell, but of light removing an inhibition the cell has placed on itself — and the cell's own homeostatic machinery taking over from there.

What this means for Tesla BioLights

Tesla BioLights is not a single-wavelength laser. The S.E.A.D. System emits the full visible-and-near-infrared line spectra of four noble gases simultaneously, in a single 15-minute session, in a regime that bears on photobiomodulation in four ways.

First, the emission lines from argon (696, 763, 811, 842 nm), neon (640, 692, 703 nm), xenon (823, 881, 904 nm), and krypton (758, 768, 811 nm) collectively bracket the entire Karu-Hamblin therapeutic window. The CCO absorption peaks fall inside the bracket. Photons at exactly the wavelengths the enzyme is tuned to receive are delivered by the device, simultaneously, every session.

Second, unlike a single-wavelength laser, the broadband plasma emission provides what Karu called a multi-target action spectrum — exciting heme a, heme a3, Cu_A, and Cu_B at their respective peaks rather than relying on a single narrowband source to do all the work.

Third, the ultra-high-frequency electromagnetic field that drives the plasma also acts as a PEMF source — addressing the bioelectric layer (Levin's research domain, covered in yesterday's essay) at the same time as the photonic layer.

Fourth, because Tesla BioLights makes no medical claims and operates in the wellness-experiential lane, the company is free to deliver the full spectrum without pretending to optimize for any single condition. The session is what it is: a fifteen-minute mitochondrial photobath plus a pulsed electromagnetic field, in a calm dim room.

Tomorrow on the Journal

Day 13 — The 600-1100 nm Window: Why Red and Near-Infrared Light Heal. A deeper look at the optical window of tissue, the dose-response curve, the Arndt-Schulz biphasic effect, the cosmetic indications cleared by the FDA, and the specific wavelengths that show up in athletic recovery protocols at the Cleveland Clinic Sports Health Center and the Andrews Institute. Then Day 14 turns to noble gas pharmacology — xenon as anesthetic and neuroprotectant, argon's HIF-1α pathway, and why these gases are real medicine before they are ever lit up as plasma.