Source
- Babcock, Montes-Cabrera, Oberhofer, Chergui, Celardo & Kurian (2024), LIT-645, read in NOTE-509: Results (Figs. 3–6), Table 1 and the Discussion; the supplement as arXiv v1 S1–S4 and Tables S1–S3.
What was shown
A model. Babcock et al., in LIT-645, treat each tryptophan as a two-level emitter (its 1La transition at 280 nm, 6 D, a single-molecule radiative lifetime of about 1.9 ns), coupled to every other through the electromagnetic field, on geometry from the tubulin crystal structure. In the single-excitation limit, a non-Hermitian Hamiltonian gives collective eigenmodes whose decay rates range far above and far below a single tryptophan’s. The brightest centriole state grows with length and saturates at max(Γ_j/γ) ≈ 4000 at vertebrate centriole lengths, and axon-like bundles of microtubules extrapolate toward about 7000. Assuming thermal equilibrium within the excited manifold and a fixed, size-independent non-radiative rate, the thermal quantum yield rises with network size.
Robustness belongs to the yield, not to the superradiance. Static disorder of about room-temperature size (W ≈ 200 cm⁻¹) cuts the centriole’s peak enhancement “from ∼3600 in the absence of disorder to ∼20” (Fig. 5), yet the quantum yield “is almost unaffected”, and some enhancement of it remains at 1000 cm⁻¹ (Fig. 4). The reason given is that disorder spreads dipole strength among neighbouring states without moving it far from the bottom of the exciton band, within k_BT. So the collective states survive room-temperature static disorder in the sense that their thermal signature does; the brightest state’s enhancement falls by more than two orders of magnitude.
A measurement. Steady-state spectroscopy of taxol-stabilised porcine microtubules in buffer gives a tryptophan-weighted quantum yield at 280 nm of 12.4 ± 1.1% for free tryptophan, 10.6 ± 0.6% for tubulin dimers and 17.6 ± 2.1% for microtubules, the last the mean of a scattering-corrected upper bound (19.5 ± 2.8%) and an uncorrected lower bound (15.7 ± 1.3%). At 295 nm the values are 11.4, 10.9 and 14.7% (Table 1). The authors call the rise from dimers to microtubules “statistically significant” and “in qualitative agreement” with the model. It could have come out otherwise: the yield could have fallen on assembly, as it does from tryptophan to the dimer.
What this does not say
- It is not evidence for Orch OR, or for anything about consciousness. The paper never mentions consciousness, Orch OR, Penrose or Hameroff. Orch OR claims that consciousness depends on orchestrated, real, gravity-related collapses of quantum states in microtubules. The states here are single electronic excitations shared across chromophores, the bright ones decaying in picoseconds; no collapse model appears and nothing concerns gravity. What it answers is one generic objection, that no collective quantum state could survive warm, disordered protein, and only for this kind of state in vitro. The collapse half of Orch OR is what Derakhshani et al. (LIT-627, unread) test against spontaneous radiation bounds, and Gao’s critique of Penrose’s gravity-collapse argument (LIT-121) is about collapse, which this account does not use.
- Superradiance itself was not observed. No lifetimes were measured, so the radiative rate is inferred from a steady-state yield. The authors’ case that the rise is not a fall in non-radiative decay is an argument (“an unlikely scenario”), not a measurement. Concentrations could not be fixed exactly, and the microtubule value rests on a scattering correction (C3 in NOTE-509, weak to moderate).
- Only dimers and microtubules were measured. Centrioles, axonemes and bundles, where the large enhancements are predicted, are simulation only.
- Dynamic disorder is not modelled. The model has static disorder only, with no exciton–phonon coupling, and a non-radiative rate that does not change with assembly size.
- Nothing is measured in neurons or tissue. The Discussion’s suggestions, axons as waveguides between superradiant emitters and “ultrafast information transfer” from metabolic photons, are supported by no result in the paper (C5 in NOTE-509, speculation).