Article abstract
Nature Neuroscience 11, 565 - 571 (2008)
Published online: 20 April 2008 | doi:10.1038/nn.2110
Quantal noise from human red cone pigment
Yingbin Fu1,3,4,5, Vladimir Kefalov1,3,4,5, Dong-Gen Luo1,3,5, Tian Xue1,3,5 & King-Wai Yau1,2,3
Abstract
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 103-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.
- Solomon H. Snyder Department of Neuroscience, Room 907 Preclinical Teaching Building, 725 North Wolfe Street, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
- Department of Ophthalmology, Room 907 Preclinical Teaching Building, 725 North Wolfe Street, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
- Center for Sensory Biology, Room 907 Preclinical Teaching Building, 725 North Wolfe Street, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
- Present addresses: Department of Ophthalmology & Visual Sciences, 65 Medical Drive, University of Utah School of Medicine, Salt Lake City, Utah 84132, USA (Y.F.) and Department of Ophthalmology & Visual Sciences, 660 S. Euclid, Washington University School of Medicine, St. Louis, Missouri 63110, USA (V.K.).
- These authors contributed equally to this work.
Correspondence to: King-Wai Yau1,2,3 e-mail: kwyau@mail.jhmi.edu
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