Stiffness and tension gradients of the hair cell’s tip-link complex in the mammalian cochlea

Tobin, M., Chaigne, A., Kalinec, F., Hudspeth, A.J. (2019) eLife 8:e43473.

Converted: 2026-04-23 (90s, 1 files, 110KB) Output: /Users/egorlyfar/BookLibrary/mineru-output/tobin-2019-elife-43473-tiplink-stiffness Original: tobin-2019-elife-43473-tiplink-stiffness.pdf Search: rag search "tip-link tension gradient"

Why We Need This

This is the canonical primary-data paper for STRC Hearing Loss biophysics. Everything in the STRC Stereocilia Bundle Mechanics Model — bundle stiffness, tip-link tension, per-gating-spring stiffness, OHC-vs-IHC gradients — either cites Tobin 2019 or needs to be reconciled against it.

Direct consumers:

• h09 hydrogel, h26 engineered homodimer, h02 piezo branches of the STRC ranking all depend on matching K_HB values from this paper
• stereocilia-mechanics.md in literature/ pulls rat OHC/IHC numbers straight from Figures 2 and 5
• Any therapeutic-window claim (“we recover X% of WT stiffness”) must be stated in units Tobin measured, otherwise it’s not auditable

For Misha specifically: his moderate SNHL is plausibly driven by a collapsed tip-link tension gradient in OHCs (HTCs maintained by STRC hold the tension that Tobin measured). If we can’t reproduce Tobin’s baseline in any model we trust, we can’t claim a rescue.

Extractable Juice

Measured parameters (rat apical cochlea, P7–P10)

Parameter	Value	Cell type	Figure
K_HB (bundle stiffness)	2.5 → 8.6 pN/nm	OHC, 1→4 kHz	Fig 2
K_HB (bundle stiffness)	1.7 → 3.8 pN/nm	IHC, 1→4 kHz	Fig 2
Single tip-link tension	5 → 34 pN	OHC, 1→4 kHz	Fig 5
γ (geometric gain)	≈ 0.14	—	Materials
EDTA protocol	local iontophoresis	—	Materials

Key equations

• Hair-bundle stiffness decomposition: $K_{\text{HB}}=K_{\text{GS}}+K_{\text{SP}}$
• Per-gating-spring stiffness: $k_{\text{GS}}=K_{\text{GS}}/({\gamma }^2\cdot N_{\text{TL}})$
• Per-pivot stiffness: $\kappa =K_{\text{SP}}\cdot h^2/N_{\text{SP}}$

Key qualitative finding

Mechanical gradients (stiffness + tension) are steeper in OHCs than IHCs, consistent with the division of labor: OHCs amplify, IHCs sense. Both steepen with CF.

How to Search

rag search "tip-link tension gradient tonotopic" -n 5
rag search "gating spring stiffness hair bundle" -n 5
rag search "EDTA iontophoresis tip-link disruption" -n 5

Connections

• Tip-Link Tension Tonotopic Gradient
• Hair Bundle Stiffness Decomposition
• Gating Spring Frequency Tuning
• STRC Stereocilia Bundle Mechanics Model
• STRC Hearing Loss
• Cochlear Amplifier as Hopf Oscillator
• Tonotopic Organization
• [part-of] Acoustics (sphere)
• [part-of] Health & Wellness (sphere, Misha thread)

Pipeline Status

• PDF converted to markdown (MinerU)
• qmd indexed (BM25 + vector search)
• RAG indexed (hierarchical + Ollama embeddings)
• Brain book note created
• Extract key ideas and formulas from Tobin 2019 ✅ 2026-04-24
• Create permanent notes from Tobin 2019 ✅ 2026-04-24 (3 atomic notes)