The molecular mechanism of thermal noise in rod photoreceptors

Samer Gozem, Igor Schapiro, Nicolas Ferré, Massimo Olivucci*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

94 Scopus citations


Spontaneous electrical signals in the retina's photoreceptors impose a limit on visual sensitivity. Their origin is attributed to a thermal, rather than photochemical, activation of the transduction cascade. Although the mechanism of such a process is under debate, the observation of a relationship between the maximum absorption wavelength (λmax) and the thermal activation kinetic constant (k) of different visual pigments (the Barlow correlation) indicates that the thermal and photochemical activations are related. Here we show that a quantum chemical model of the bovine rod pigment provides a molecular-level understanding of the Barlow correlation. The transition state mediating thermal activation has the same electronic structure as the photoreceptor excited state, thus creating a direct link between λmax and k. Such a link appears to be the manifestation of intrinsic chromophore features associated with the existence of a conical intersection between its ground and excited states.

Original languageAmerican English
Pages (from-to)1225-1228
Number of pages4
Issue number6099
StatePublished - 7 Sep 2012
Externally publishedYes


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