Collapse, Not Computation · source record · paper
Electronic Energy Migration in Microtubules
Kalra, Aarat P.; Benny, Alfy; Travis, Sophie M.; Zizzi, Eric A.; Morales-Sanchez, Austin; Oblinsky, Daniel G.; Craddock, Travis J. A.; Hameroff, Stuart R.; MacIver, M. Bruce; Tuszyński, Jack A.; Petry, Sabine; Penrose, Roger; Scholes, Gregory D. · 2023
AI-verified citationSRC-KALRA-2023
- identifier / locator
- ACS Central Science 9(3): 352–361. DOI: 10.1021/acscentsci.2c01114
- verification note
- Verified via Crossref and PubMed (PMID 36968538, PMCID PMC10037452); abstract read directly (2026-08-22 run). CORRECTION: Eugene's primer cites the pages as "9(3), 519–529"; the published range is 352–361. Volume, issue, and year in the primer are correct. Open access (ACS author-choice), so the full text is publicly checkable.
- reliability notes
- The single most important experiment for the biological half of the theory: senior author Gregory Scholes is a mainstream ultrafast-spectroscopy figure at Princeton, and the work is published in a high-quality general chemistry journal.
- Independence caveat that proponent summaries usually omit: Hameroff and Penrose are both co-authors, as are Craddock and Tuszyński. This is not a disinterested outside laboratory testing Orch OR — it is a collaboration including the theory's authors, run in an outside laboratory.
- The abstract's own framing is modest — 'microtubules are, unexpectedly, effective light harvesters' — and makes no coherence, entanglement, or consciousness claim.
- No independent exact replication as of this import.
Evidence drawn from this source
▲Supports· moderateORCH-E001
Electronic excitation diffuses ~6.6 nm in microtubules, beyond Förster prediction
- what the source states
- The abstract states: "By studying how the quencher concentration alters tryptophan autofluorescence lifetimes, we demonstrate that electronic energy can diffuse over 6.6 nm in microtubules"; that "this diffusion length is not sufficiently explained by accepted Förster resonance energy transfer models, even after accounting for the contribution of tryptophan-tyrosine interactions"; and concludes that "microtubules are, unexpectedly, effective light harvesters." Diffusion was observed to depend on polymerization state but not on protofilament number.
- what we infer
- This is the strongest single piece of experimental support for the biological half of Orch OR, and its limits are as important as its content. The measured length scale is roughly one tubulin dimer, and the quantity measured is an excitation diffusion length, not a coherence time — the paper's modeling explicitly includes an incoherent energy-migration comparison. Structure-dependence (polymerization matters, protofilament architecture does not) argues against artifact. Treated here as strong evidence that microtubules are electronically nontrivial (ORCH-C013) and as no evidence at all for the millisecond coherence ORCH-C010 requires.
- limitations
- Diffusion length is inferred from concentration-dependent quenching, not directly imaged.
- Not replicated by an independent laboratory as of this import.
- Purified in vitro microtubules, not neurons: no MAPs, no cytosolic crowding, no membrane environment.
- Independence caveat: Hameroff, Penrose, Craddock, and Tuszyński are all co-authors, so this is a collaboration including the theory's authors rather than an outside test of it.
▲Supports· moderateORCH-E002
Etomidate and isoflurane reduce microtubule exciton diffusion
- what the source states
- The abstract states: "We also demonstrate that the presence of the anesthetics etomidate and isoflurane reduce exciton diffusion." The concluding sentence is that these results "may have implications in various physiological processes, including in anesthetic action." The deep-research report gives the reduced diffusion lengths as approximately 5.6 nm (etomidate) and 5.8 nm (isoflurane) at 50 μM against the 6.6 nm baseline; those specific values are from the paper body, which this import did not read directly, and are recorded here as reported rather than as verified.
- what we infer
- A direct experimental link between clinical anesthetics and a measured microtubule physical property — the observation that makes the anesthesia arm of Orch OR worth testing rather than merely worth asserting. The effect is modest, roughly a 13% reduction if the reported values are right, and the concentration is at or above the clinical range. Crucially this establishes that anesthetics perturb microtubule photophysics (ORCH-C011) without establishing that the perturbation has anything to do with unconsciousness; the specificity control in the same paper (ORCH-E003) is what stops this from carrying more weight.
- limitations
- Two agents only; no potency series, no nonimmobilizer controls, no hydrophobic non-anesthetic controls.
- Free aqueous concentration not established, so effective exposure is uncertain.
- Specific reduced values not verified against the paper body by this import.
- In vitro purified microtubules; no demonstrated relationship to any behavioral endpoint.
▼Undermines· moderateORCH-E003
Picrotoxin, a convulsant, produced a comparable effect on the same assay
- what the source states
- The deep-research report states that the same study found picrotoxin — a GABA_A antagonist and convulsant, pharmacologically the opposite of an anesthetic — reducing tryptophan quenching comparably to the anesthetics tested. This detail is from the paper body rather than the abstract and was not directly verified by this import; it is recorded because it is the single most important qualification on ORCH-E002 and omitting it would misrepresent the experiment.
- what we infer
- If a convulsant and two anesthetics all suppress the assay, then what is being measured is the perturbability of microtubule photophysics by small hydrophobic molecules, not something specific to anesthesia. This is the sharpest available objection to the anesthesia arm and it comes from inside the theory's own flagship experiment rather than from critics — which is to the authors' credit for reporting it. It does not show the anesthetic effect is spurious; it shows the experiment as performed cannot distinguish an anesthesia-specific mechanism from general pharmacological perturbation. Only a potency series with proper controls can.
- limitations
- Detail not directly verified against the paper by this import; carried as reported by the deep-research report.
- A single comparison compound, not a systematic specificity panel — the absence of specificity is not itself established, only unaddressed.