Quantal noise from human red cone pigment

Yingbin Fu, Vladimir Kefalov, Dong Gen Luo, Tian Xue, King Wai Yau

Research output: Contribution to journalArticlepeer-review

64 Scopus citations


The rod pigment, rhodopsin, shows spontaneous isomerization activity. This quantal noise produces a dark light of ∼0.01 photons s-1 rod -1 in human, setting the threshold for rod vision. The spontaneous isomerization activity of human cone pigments has long remained a mystery because the effect of a single isomerized pigment molecule in cones, unlike that in rods, is small and beyond measurement. We have now overcome this problem by expressing human red cone pigment transgenically in mouse rods in order to exploit their large single-photon response, especially after genetic removal of a key negative-feedback regulation. Extrapolating the measured quantal noise of transgenic cone pigment to native human red cones, we obtained a dark rate of ∼10 false events s-1 cone-1, almost 10 3-fold lower than the overall dark transduction noise previously reported in primate cones. Our measurements provide a rationale for why mammalian red, green and blue cones have comparable sensitivities, unlike their amphibian counterparts.

Original languageEnglish
Pages (from-to)565-571
Number of pages7
JournalNature neuroscience
Issue number5
StatePublished - May 29 2008


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