The unified molecular transducer: every special sense is an R19 bistable channel switch
Every special-sense transducer is the same physical object: a cooperative or bistable ion channel — an R19 double-well switch. The photoreceptor (CNG), hair-cell (MET), and taste (TAS1R→TRPM5) channels are each modelled as bistable with a discontinuous flip (bistability holds by construction for any positive stiffness — a property of the model, not a verification); olfaction shares the rod's CNG superfamily. One switch primitive underlies five senses.
The transduction model tests each channel as an R19 double-well and finds bistability with a discontinuous flip and hysteresis for every transducer carrying a measured γ (by construction for any positive stiffness; the γ used are those of the master genes RAX, SOX2, TAS1R3, not of the channel genes). Sigmoid maximum slopes of 3.1–3.3 (cooperative gating) are a code output that depends on the sampling grid (21/41/81/161 points → 2.39/3.32/4.54/6.07; the slope diverges at the fold); the observed Hill coefficient ≈3 is an observation about the channel, not reproduced by the model. Channel identity and accession are cited [L]; γ for the effector genes is owned by the DNA pipeline (SSOT), entered as an honest to-measure input rather than invented.
The central result of the molecular layer is a unification: the transducers of vision, hearing, taste, and smell are not four mechanisms but four instances of one. Each is a cooperative or bistable ion channel, which is exactly the R19 double-well — two stable states separated by a barrier, with an all-or-none flip between them.
What makes a sensory channel a switch?
A transducer is a switch when it has two stable states and crosses between them sharply rather than gradually. Cast as an R19 double-well and driven, every channel with a vendored γ shows the three switch signatures: bistability (two stable conductances), a discontinuous flip, and hysteresis (the up- and down-thresholds differ). The hysteresis widths sit around 1.35–1.49. The barriers in the table below are γ²/4 of the master genes (RAX 0.529, SOX2 0.531, TAS1R3 0.605), not of the channel genes, whose γ is still to be measured; any positive stiffness gives bistability by construction, so this is a property of the model, not a verification of the channels.
| sense | channel | genes (cited) | max slope (41-pt grid) | barrier (master-gene γ²/4) | grade |
|---|---|---|---|---|---|
| vision | rod CNG (cyclic-nucleotide-gated) | CNGA1, CNGB1 | 3.32 | 0.529 | consistency (code) |
| hearing | hair-cell MET (gating-spring) | TMC1, PCDH15, CDH23 | 3.31 | 0.531 | consistency (code) |
| taste | T1R GPCR → TRPM5 channel | TAS1R2/3, TRPM5 | 3.12 | 0.605 | consistency (code) |
| smell | olfactory CNG (cAMP-gated) | CNGA2, ADCY3 | deferred | — | [O]→ |
Cooperative gating makes the flip sharp
Maximum slopes of 3.1–3.3 are a code output on a 41-point grid and depend on it (21/41/81/161 points → 2.39/3.32/4.54/6.07; the slope diverges at the fold). The cooperative gating seen physiologically (Hill coefficient ≈3) is an observation about the channel (cited); the model does not reproduce it. Cooperativity is what converts a smooth change in stimulus into an all-or-none change in conductance, so each transducer behaves as a clean threshold detector rather than a graded one — the property that lets a single photon or a sub-nanometre bundle deflection produce a definite response.
Vision and smell share a literal common transducer
The olfactory channel CNGA2 belongs to the same cyclic-nucleotide-gated superfamily as the rod's CNGA1. Two senses therefore run on one switch primitive, with smell using cAMP where vision uses cGMP — the single most direct evidence that the special senses share a transducer, developed in phototransduction and chemodetection.