title: Human infrared vision is triggered by two-photon chromophore isomerization.
abstract: Vision relies on photoactivation of visual pigments in rod and cone photoreceptor cells of the retina. The human eye structure and the absorption spectra of pigments limit our visual perception of light. Our visual perception is most responsive to stimulating light in the 400- to 720-nm (visible) range. First, we demonstrate by psychophysical experiments that humans can perceive infrared laser emission as visible light. Moreover, we show that mammalian photoreceptors can be directly activated by near infrared light with a sensitivity that paradoxically increases at wavelengths above 900 nm, and display quadratic dependence on laser power, indicating a nonlinear optical process. Biochemical experiments with rhodopsin, cone visual pigments, and a chromophore model compound 11-cis-retinyl-propylamine Schiff base demonstrate the direct isomerization of visual chromophore by a two-photon chromophore isomerization. Indeed, quantum mechanics modeling indicates the feasibility of this mechanism. Together, these findings clearly show that human visual perception of near infrared light occurs by two-photon isomerization of visual pigments.
authors.affiliation: Department of Medical Devices, Polgenix, Inc., Cleveland, OH 44106;
authors.forename: Grazyna
authors.initials: G
authors.lastname: Palczewska
authors.affiliation: Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, MO 63110;
authors.forename: Frans
authors.initials: F
authors.lastname: Vinberg
authors.affiliation: Faculty of Physics, Astronomy and Informatics, Institute of Physics, Nicolaus Copernicus University, 87-100 Torun, Poland;
authors.forename: Patrycjusz
authors.initials: P
authors.lastname: Stremplewski
authors.affiliation: Department of Chemistry and Biochemistry, University of Bern, CH-3012 Bern, Switzerland;
authors.forename: Martin P
authors.initials: MP
authors.lastname: Bircher
authors.affiliation: Department of Pharmacology, Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106; and.
authors.forename: David
authors.initials: D
authors.lastname: Salom
authors.affiliation: Faculty of Physics, Astronomy and Informatics, Institute of Physics, Nicolaus Copernicus University, 87-100 Torun, Poland;
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Komar
authors.affiliation: Department of Pharmacology, Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106; and.
authors.forename: Jianye
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Department of Chemistry and Centre for Theoretical and Computational Chemistry, University of Oslo, N-0315 Oslo, Norway michele.cascella@kjemi.uio.no max@fizyka.umk.pl kefalov@vision.wustl.edu kxp65@case.edu.
authors.forename: Michele
authors.initials: M
authors.lastname: Cascella
authors.affiliation: Faculty of Physics, Astronomy and Informatics, Institute of Physics, Nicolaus Copernicus University, 87-100 Torun, Poland; michele.cascella@kjemi.uio.no max@fizyka.umk.pl kefalov@vision.wustl.edu kxp65@case.edu.
authors.forename: Maciej
authors.initials: M
authors.lastname: Wojtkowski
authors.affiliation: Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, MO 63110; michele.cascella@kjemi.uio.no max@fizyka.umk.pl kefalov@vision.wustl.edu kxp65@case.edu.
authors.forename: Vladimir J
authors.initials: VJ
authors.lastname: Kefalov
authors.affiliation: Department of Pharmacology, Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106; and michele.cascella@kjemi.uio.no max@fizyka.umk.pl kefalov@vision.wustl.edu kxp65@case.edu.
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Palczewski
mesh_terms: D065638:Absorption, Radiation; D000328:Adult; D000818:Animals; D002417:Cattle; D003198:Computer Simulation; D004596:Electroretinography; D005260:Female; D006801:Humans; D007259:Infrared Rays; D007536:Isomerism; D007834:Lasers; D008297:Male; D051379:Mice; D017785:Photons; D020419:Photoreceptor Cells, Vertebrate / Q000502:physiology*; D011601:Psychophysics; D012243:Rhodopsin / Q000737:chemistry*; D014785:Vision, Ocular / Q000502:physiology*
chemical_list: D012243:Rhodopsin
keywords: multiscale modeling; rhodopsin; transretinal electrophysiology; two-photon absorption; visual pigment