STRC Research

tectorial-membrane

9 min read

Tectorial membrane mechanics — validated parameters

Source agent: h02 parameter provenance audit (Sonnet 4.6), 2026-04-23. Consumer: piezo_voltage_budget.py, piezo_phase2_frequency_bundle.py.

Structural parameters

ParameterValueSourceConditionsStatusNotes
TM thickness (mouse, apical)~30–50 µmestimate from human data—⚠Human TM thickness 19 µm (hook) to 64 µm (upper middle). Mouse TM thinner. NEEDS primary murine measurement. Not sourced this turn.
TM Young’s modulus (fiber modulus, AFM)~1 kPa (base), smaller apex2026-04-25-gavara-2009-tm-collagen-anisotropy-afm (Gavara & Chadwick 2009, PLoS One 4:e4877, PMID 19293929)mouse TM, AFM + anisotropic model✅ CORRECTEDCritical correction: Prior citation “Masaki K et al. 2009 PLOS One 4:e4877 — TM Young’s modulus 24 kPa apical, 210 kPa basal” was WRONG on author (Gavara not Masaki) AND wrong on values (Gavara reports fiber modulus ~1 kPa, not 24 kPa). The 24–210 kPa Young’s modulus values lack a confirmed primary source and must be re-sourced.
TM Young’s modulus (basal, apical)24.3 ± 25.2 kPa (basal), 5.1 kPa (middle), 1.9 kPa (apical)2026-04-25-teudt-2014-tm-bm-stiffness-cba-mouse (Teudt & Richter 2014, J Assoc Res Otolaryngol 15:675, PMID 24865766)CBA/CaJ mouse, probe indentation ex vivo✅ SOURCED (2026-04-25 follow-up)Critical correction: “Masaki K 2009 PLoS One 4:e4877” is a phantom (= Gavara & Chadwick 2009, ~1 kPa fiber modulus). Real source for 24 kPa = Teudt & Richter 2014: TM Young’s modulus basal 24.3 kPa. Note: 24 kPa is BASAL turn, not apical. Apical = 1.9 kPa. The “210 kPa” figure has NO confirmed primary source — not in Teudt 2014, Shoelson 2004, or Gavara 2009.
TM shear modulus G’ (AFM inhomogeneity)2.0 ± 1.2 kPa (Hertz model), 6.5 ± 4.2 kPa (Bilodeau model)2026-04-25-shoelson-2004-tm-elasticity-inhomogeneity-biophysj (Shoelson et al. 2004, Biophys J 87:2768, PMID 15454468)Guinea pig TM, AFM, 5 radial zones✅ paper note exists (2026-04-25)Shear modulus (not Young’s modulus); guinea pig not mouse. Zone 4 (OHC region) softest ~4 kPa. Does NOT support 24–210 kPa Young’s modulus range.
TM Young’s modulus “210 kPa”SOURCE NOT FOUNDunattributed—❌ NO PRIMARY SOURCEExhaustive search 2026-04-25: Teudt 2014 max 24.3 kPa (basal, ±25.2); Shoelson 2004 shear 2–6.5 kPa; Gavara 2009 fiber ~1 kPa; Gueta 2008 vertical 300 kPa (but that is vertical compressive modulus, not Young’s). The 210 kPa figure does not appear in any retrieved paper. Must be treated as in-house assumption or removed from scripts.
TM shear storage modulus G′16 kPa (apical) – 40 kPa (basal)2026-04-25-ghaffari-2007-tm-traveling-wave-pnas (Ghaffari et al. 2007, PNAS 104:16510, PMID 17925447)isolated mouse TM, 2–20 kHz✅ paper note existsG′ = 16 kPa apical, 40 kPa basal. Shear viscosity η = 0.18 Pa·s (apical), 0.33 Pa·s (basal). Confirms TM is 4–5 orders of magnitude softer than PVDF-TrFE (3 GPa).
TM shear anisotropy (radial:longitudinal)1.8 ± 0.7 (WT) → 1.0 ± 0.1 (Col11a2 KO)2026-04-25-masaki-2009-tm-col11a2-anisotropy (Masaki et al. 2009, Biophys J 96:4717, PMID 19486694)mouse TM, shear impedance✅ paper note existsCollagen XI organizes radial fibrils; KO eliminates anisotropy. Radial direction 1.8× stiffer than longitudinal in WT. Relevant to conformal film deposition axis.
TM vertical vs lateral stiffnessvertical 300 kPa >> lateral (45–75 kPa)2026-04-25-gueta-2008-tm-anisotropy-stereocilia-deflection (Gueta et al. 2008, Biophys J 94:4570, PMID 18310237)mouse TM, force spectroscopy✅ CORRECTEDCorrection: Prior citation “Gueta 2008 Biophys J 95:4948” — wrong volume and pages. Correct: Biophys J 94(11):4570–4576. Vertical modulus 300 kPa; lateral Ex=45, Ey=75 kPa; anisotropy 4–6×.
TM water content~97%established—✅ referenceTM is essentially a hydrogel; determines poroelastic behavior.
TM radial collagen fiber diameter~1 µm (base), ~0.4 µm (apex)2026-04-25-gavara-2009-tm-collagen-anisotropy-afm (Gavara & Chadwick 2009, Fig 6)mouse TM, AFM imaging✅ paper note existsFiber spacing gap 0.6 µm (base), 0.75 µm (apex). Source of radial mechanical anisotropy.

TM displacement vs SPL

These values are used in TM_DISP_60dB dict in piezo_phase2_frequency_bundle.py. Scripts cite “Gueta 2006, Ren 2011” without page/figure.

FrequencyValue (60 dB SPL)SourceStatusNotes
200 Hz30 nm (model)IN-HOUSE ASSUMPTION — no primary measurement at this frequency+SPL combination—⚠ MODEL ASSUMPTION
1000 Hz20 nm (model)IN-HOUSE ASSUMPTION — no primary measurement at this frequency+SPL combination—⚠ MODEL ASSUMPTION
4000 Hz10 nm (model)IN-HOUSE ASSUMPTION—⚠ MODEL ASSUMPTION
8000 Hz5 nm (model)IN-HOUSE ASSUMPTION—⚠ MODEL ASSUMPTION

Revised context (2026-04-25 follow-up audit): “Gueta 2006” is a phantom — the paper is Gueta 2008 (Biophys J 94:4570), which measures TM stiffness anisotropy not absolute displacement. “Ren 2011” was not found; Ren 2002 PNAS (PMID 12461165) measures BM wave phase in gerbil basal turn, not TM displacement in nm. Gao 2014 J Neurophysiol (PMID 24920025) uses OCT on mouse apical cochlea but reports normalized sensitivity ratios, not absolute nm.

Follow-up search result (2026-04-25 blocker closure): The best available primary source for absolute TM displacement is Lee et al. 2015 PNAS 112:3128 (PMID 25737536 — Oghalai lab, volumetric OCT): TM peak magnitude ~20 nm at 20 dB SPL and ~90 nm at 80 dB SPL in mouse cochlea at ~7.5–9 kHz CF. Interpolating at 60 dB SPL gives ~35–40 nm, not 30 nm. The exact frequency-dependent table (30→5 nm across 200→8000 Hz) in the h02 scripts is a model parameterization with no single primary paper. Cooper & Rhode 1996 J Neurophysiol was searched but not retrievable via PubMed open-access — its content cannot be verified for absolute nm values without full-text access. Gummer, Hemmert & Zenner 1996 PNAS 93:8727 (PMID 8710939) measures TM in two orthogonal directions in guinea pig but full-text nm values not confirmed via PMC.

Verdict: The 5–30 nm range at 60 dB SPL must be flagged as an IN-HOUSE MODEL ASSUMPTION. The values are order-of-magnitude consistent with Lee 2015 and the general cochlear literature, but the specific frequency-dependent table (TM_DISP_60dB dict) in piezo_phase2_frequency_bundle.py has no single primary citation. Scripts must carry a WARNING comment explicitly stating this. The audit flag on “Gueta 2006” = phantom citation is confirmed.

Papers retrieved (2026-04-25 lit audit + blocker closure)

PriorityPaperStatusKey finding
P1Ghaffari R et al. (2007) PNAS 104:16510, PMID 17925447✅ 2026-04-25-ghaffari-2007-tm-traveling-wave-pnasG′ = 16 kPa apical, 40 kPa basal; η = 0.18–0.33 Pa·s
P1”Masaki K et al. 2009 PLOS One 4:e4877” → WRONG CITATION✅ CORRECTEDThat DOI belongs to Gavara & Chadwick 2009
P1Gavara & Chadwick (2009) PLoS One 4:e4877, PMID 19293929✅ 2026-04-25-gavara-2009-tm-collagen-anisotropy-afmFiber modulus ~1 kPa (NOT 24 kPa); large anisotropy
P1Masaki K et al. (2009) Biophys J 96:4717, PMID 19486694✅ 2026-04-25-masaki-2009-tm-col11a2-anisotropyActual Masaki 2009: shear impedance anisotropy; Col11a2 collagen XI
P2Gueta R et al. (2008) Biophys J 94:4570, PMID 18310237✅ CORRECTED 2026-04-25-gueta-2008-tm-anisotropy-stereocilia-deflectionVol 94 not 95; pages 4570 not 4948; no absolute nm displacement values
P2”Ren T (2002) Nat Neurosci 5:169” → WRONG JOURNAL✅ CORRECTED: Ren 2002 PNAS 99:17101, PMID 124611652026-04-25-ren-2002-bm-traveling-wave-pnas — BM wave in gerbil basal; no TM nm values
P3Gao SS et al. (2014) J Neurophysiol 112:1192, PMID 24920025✅ 2026-04-25-gao-2014-organ-corti-oct-vibrationOCT organ of Corti vibration; normalized not absolute nm
BlockerTeudt IU & Richter CP (2014) JARO 15:675, PMID 24865766✅ NEW 2026-04-25-teudt-2014-tm-bm-stiffness-cba-mouseReal source for 24 kPa TM Young’s modulus (basal, CBA/CaJ mouse). Phantom “Masaki 2009” attribution CLOSED.
BlockerShoelson B et al. (2004) Biophys J 87:2768, PMID 15454468✅ NEW 2026-04-25-shoelson-2004-tm-elasticity-inhomogeneity-biophysjShear modulus 2–6.5 kPa (guinea pig); does NOT support 24–210 kPa. Context only.
BlockerLee HY et al. (2015) PNAS 112:3128, PMID 25737536context only (no paper note needed)Closest primary data for TM nm displacement: ~20 nm at 20 dB, ~90 nm at 80 dB. Interpolation to 60 dB → ~35–40 nm. Does not match script table exactly. TM displacement demoted to model assumption.
⚠Gummer AW, Hemmert W, Zenner HP (1996) PNAS 93:8727, PMID 8710939not retrieved (PNAS, not PMC open-access; Anna’s does not index)Measured TM motion in guinea pig in two directions; full-text nm values not confirmed. Could not verify absolute nm values.

Remaining open gaps (updated 2026-04-25 blocker closure)

  • TM Young’s modulus 24 kPa (basal): RESOLVED — source is Teudt & Richter 2014 JARO (PMID 24865766), CBA/CaJ mouse, basal turn 24.3 ± 25.2 kPa. Note: this is BASAL, not apical. Apical = 1.9 kPa.
  • TM Young’s modulus 210 kPa: UNRESOLVED — no primary source found after exhaustive search. Not in Teudt 2014, Shoelson 2004, Gavara 2009, or Gueta 2008. Gueta 2008 gives vertical compressive modulus ~300 kPa (different loading axis), which may be the origin of a number in that range, but 210 kPa specifically is unsourced. Flag as MODEL ASSUMPTION or remove from scripts.
  • TM displacement 5–30 nm at 60 dB SPL: DEMOTED TO IN-HOUSE MODEL ASSUMPTION — closest primary source is Lee et al. 2015 PNAS (PMID 25737536): ~20 nm at 20 dB, ~90 nm at 80 dB. The specific TM_DISP_60dB frequency table in scripts is a model parameterization, not a primary measurement. Cooper & Rhode 1996 and Gummer 1996 could not be confirmed via open-access full text. Scripts must carry explicit WARNING.
  • OHC specific membrane resistance (~kΩ·cm²): No primary paper; gap remains open.

Relevance to h02 piezo hypothesis

The TM is the proposed substrate for PVDF-TrFE film deposition. Critical parameters for hypothesis feasibility:

  1. TM stiffness (confirmed by lit audit 2026-04-25): Ghaffari 2007 gives G′ = 16–40 kPa (shear); Gueta 2008 gives vertical Young’s modulus ~300 kPa, lateral ~45–75 kPa; Gavara 2009 fiber modulus ~1 kPa. The frequently cited “24–210 kPa Young’s modulus” lacks a confirmed primary source after audit. In all cases PVDF-TrFE (3 GPa) is 10⁴–10⁵× stiffer than TM. The film will not load-couple efficiently — mechanical mismatch confirmed and quantified. This remains a potential hypothesis-level mechanical flaw not modeled in scripts.

  2. TM surface topology: radially-oriented collagen fibers provide directionality. A conformal film would need to deposit along the radial axis to use TM displacement most efficiently.

  3. TM displacement magnitudes (5–30 nm at 60 dB) are the mechanical input to the piezo model. These are the most uncertain values in the chain.

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