Shoelson et al. 2004 — Evidence and implications of inhomogeneity in tectorial membrane elasticity
AUDIT NOTE (2026-04-25): Candidate paper for the h02 TM Young’s modulus attribution. Does NOT support the 24–210 kPa range used in scripts. Reports shear modulus (not Young’s modulus) of 2–6.5 kPa in guinea pig TM. Confirmed as a real, high-quality paper but not the source for 24 kPa or 210 kPa. The confirmed source for 24 kPa (basal TM) is Teudt & Richter 2014 JARO.
TL;DR. AFM-based shear modulus mapping across five radial zones of guinea pig TM. Aggregate shear modulus G’ = 2.00 ± 1.24 kPa (microsphere probe, Hertz model) or 6.54 ± 4.18 kPa (pyramid probe, Bilodeau model). Minimum near OHC attachment zone (zone 4 ~4.36 kPa pyramid). The inhomogeneity — lower stiffness near hair cells — may protect hair bundles and improve coupling efficiency.
Key finding. TM shear modulus is inhomogeneous radially and longitudinally, with zones near sensory hair cells measurably softer. This is functionally significant for stereocilia coupling. Values in the 1–7 kPa range (depending on probe geometry and contact model), consistent with Gavara 2009 fiber modulus (~1 kPa) and Ghaffari 2007 shear modulus (16–40 kPa).
Numbers that matter
| Parameter | Value | Units | Source location | Conditions |
|---|---|---|---|---|
| TM shear modulus G’ (microsphere, Hertz) | 2.00 ± 1.24 | kPa | Table 1, Results | Guinea pig, AFM, 10 animals, ~1000 curves |
| TM shear modulus G’ (pyramid, Bilodeau) | 6.54 ± 4.18 | kPa | Table 1, Results | Guinea pig, same preparation |
| Zone 4 shear modulus (OHC region, pyramid) | 4.36 | kPa | Results | Zone 4 = OHC attachment site |
| Individual zone range | ~1.5–3.5 | kPa | Results (microsphere) | Zones 1–5, three longitudinal regions |
| Number of animals | 10 | — | Methods | Juvenile female pigmented guinea pig 150–200 g |
| Number of force curves | ~1000 | — | Methods | Across all zones and regions |
| TM Young’s modulus reported | NOT reported | — | — | Only shear modulus G’; Young’s E not derived |
Relation to h02 parameter. Scripts used “24 kPa” and “210 kPa” attributed to “Masaki 2009.” Shoelson 2004 reports shear modulus 2–6.5 kPa, not Young’s modulus, and in guinea pig not mouse. Converting G’ to E requires a Poisson ratio assumption (E = 2G’(1+ν); for ν=0.5 hydrogel, E ≈ 3G’ → ~6–20 kPa range), which would place upper estimates near but below 24 kPa. The 24 kPa basal TM Young’s modulus is best sourced to Teudt & Richter 2014 (CBA/CaJ mouse, direct indentation).
Limitations
- Guinea pig, not mouse. TM mechanics differ by species and preparation.
- AFM probe geometry strongly affects reported modulus (2× difference between pyramid and microsphere probes).
- Shear modulus ≠ Young’s modulus without Poisson ratio assumption.
Connections
[source]tectorial-membrane — shear modulus 2–6.5 kPa; does NOT source 24–210 kPa Young’s modulus[see-also]2026-04-25-teudt-2014-tm-bm-stiffness-cba-mouse — confirmed source for 24 kPa TM Young’s modulus (basal mouse)[see-also]2026-04-25-gavara-2009-tm-collagen-anisotropy-afm — fiber modulus ~1 kPa; same AFM approach[see-also]2026-04-25-ghaffari-2007-tm-traveling-wave-pnas — dynamic G’ 16–40 kPa (different loading regime)[applies]STRC Piezoelectric TM Bioelectronic Amplifier