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Cone Opsin
Vertebrate visual opsins are a subclass of ciliary opsins and mediate vision in vertebrates. They include the opsins in human rod and cone cells. They are often abbreviated to ''opsin'', as they were the first opsins discovered and are still the most widely studied opsins. Opsins Opsin refers strictly to the apoprotein (without bound retinal). When an opsin binds retinal to form a holoprotein, it is referred to as Retinylidene protein. However, the distinction is often ignored, and opsin may refer loosely to both (regardless of whether retinal is bound). Opsins are G-protein-coupled receptors (GPCRs) and must bind retinal — typically 11-''cis''-retinal — in order to be photosensitive, since the retinal acts as the chromophore. When the Retinylidene protein absorbs a photon, the retinal isomerizes and is released by the opsin. The process that follows the isomerization and renewal of retinal is known as the visual cycle. Free 11-''cis''-retinal is photosensitiv ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rhodopsin 3D
Rhodopsin, also known as visual purple, is a protein encoded by the ''RHO'' gene and a G-protein-coupled receptor (GPCR). It is a light-sensitive receptor protein that triggers visual phototransduction in rod cells. Rhodopsin mediates dim light vision and thus is extremely sensitive to light. When rhodopsin is exposed to light, it immediately photobleaches. In humans, it is fully regenerated in about 30 minutes, after which the rods are more sensitive. Defects in the rhodopsin gene cause eye diseases such as retinitis pigmentosa and congenital stationary night blindness. History Rhodopsin was discovered by Franz Christian Boll in 1876. The name rhodopsin derives from Ancient Greek () for "rose", due to its pinkish color, and () for "sight". It was coined in 1878 by the German physiologist Wilhelm Friedrich Kühne (1837–1900). When George Wald discovered that rhodopsin is a holoprotein, consisting of retinal and an apoprotein, he called it opsin, which today ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Theria
Theria ( or ; ) is a scientific classification, subclass of mammals amongst the Theriiformes. Theria includes the eutherians (including the Placentalia, placental mammals) and the metatherians (including the marsupials) but excludes the egg-laying monotremes and various extinct mammals evolving prior to the common ancestor of placentals and marsupials. Characteristics Therians give birth to live young without a shelled egg (biology), egg. This is possible thanks to key proteins called Syncytin-1, syncytins which allow exchanges between the mother and its offspring through a placenta, even Marsupial#Reproductive system, rudimental ones such as in marsupials. Genetic studies have suggested a viral origin of syncytins through the Endogenous retrovirus, endogenization process. The marsupials and the placentals evolved from a common therian ancestor that gave live birth by suppressing the mother's immune system. While the marsupials continued to give birth to an underdeveloped fe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Monotreme
Monotremes () are mammals of the order Monotremata. They are the only group of living mammals that lay eggs, rather than bearing live young. The extant monotreme species are the platypus and the four species of echidnas. Monotremes are typified by structural differences in their brains, jaws, digestive tract, reproductive tract, and other body parts, compared to the more common mammalian types. Although they are different from other living mammals in that they lay eggs, female monotremes are like other mammals in that they nurse their young with milk. Monotremes have been considered by some authors to be members of Australosphenida, a clade that contains extinct mammals from the Jurassic and Cretaceous of Madagascar, South America, and Australia, but this categorization is disputed and their taxonomy is under debate. All extant species of monotremes are indigenous to Australia and New Guinea, although they were also present during the Late Cretaceous and Paleocene epochs in s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
OPN1SW
Blue-sensitive opsin is a protein that in humans is encoded by the ''OPN1SW'' gene. The OPN1SW gene provides instructions for making a protein that is essential for normal color vision. This protein is found in the retina, which is the light-sensitive tissue at the back of the eye. The OPN1SW gene provides instructions for making an opsin pigment that is more sensitive to light in the blue/violet part of the visible spectrum (short-wavelength light). Cones with this pigment are called short-wavelength-sensitive or S cones. In response to light, the photopigment triggers a series of chemical reactions within an S cone. These reactions ultimately alter the cell's electrical charge, generating a signal that is transmitted to the brain. The brain combines input from all three types of cones to produce normal color vision. See also * Opsin Animal opsins are G-protein-coupled receptors and a group of proteins made light-sensitive via a chromophore, typically retinal. When bound to r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
OPN1MW
Green-sensitive opsin is a protein that in humans is encoded by the ''OPN1MW'' gene. OPN1MW2 is a similar opsin. The OPN1MW gene provides instructions for making an opsin pigment that is more sensitive to light in the middle of the visible spectrum (yellow/green light). See also * Opsin * OPN1LW OPN1LW is a gene on the X chromosome that encodes for long wave sensitive (LWS) opsin, or red cone photopigment. The OPN1LW gene provides instructions for making an opsin pigment that is more sensitive to light in the yellow/orange part of the vis ... References Further reading * * * * * * * * * * * * * External links GeneReviews/NIH/NCBI/UW entry on Red-Green Color Vision Defects G protein-coupled receptors Color vision {{transmembranereceptor-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
OPN1LW
OPN1LW is a gene on the X chromosome that encodes for long wave sensitive (LWS) opsin, or red cone photopigment. The OPN1LW gene provides instructions for making an opsin pigment that is more sensitive to light in the yellow/orange part of the visible spectrum (long-wavelength light). The gene contains 6 exons with variability that induces shifts in the spectral range. OPN1LW is subject to homologous recombination with OPN1MW, as the two have very similar sequences. These recombinations can lead to various vision problems, such as red-green colourblindness and blue monochromacy. The protein encoded is a G-protein coupled receptor with embedded 11-''cis''-retinal, whose light excitation causes a cis-trans conformational change that begins the process of chemical signalling to the brain. It is responsible for perception of visible light in the yellow-green range on the visible spectrum (around 500-570nm). Gene OPN1LW produces red-sensitive opsin, while its counterparts, OPN1MW ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photopic Vision
Photopic vision is the vision of the eye under well-lit conditions (luminance levels from 10 to 108 cd/m2). In humans and many other animals, photopic vision allows color perception, mediated by cone cells, and a significantly higher visual acuity and temporal resolution than available with scotopic vision. The human eye uses three types of cones to sense light in three bands of color. The biological pigments of the cones have maximum absorption values at wavelengths of about 420 nm (blue), 534 nm (bluish-green), and 564 nm (yellowish-green). The color of the pure signal of the cones could be described as violet, blue-green, and scarlet red, respectively, but, in their wavelengths of maximum absorption other cones are activated as well. The sensitivity ranges of the conecells overlap to provide vision throughout the visible spectrum. The maximum efficacy is 683 lm/W at a wavelength of 555 nm (green). By definition, light at a frequency of hertz ha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Iodopsin
Vertebrate visual opsins are a subclass of ciliary opsins and mediate visual system, vision in vertebrates. They include the opsins in human rod cell, rod and cone cells. They are often abbreviated to ''opsin'', as they were the first opsins discovered and are still the most widely studied opsins. Opsins Opsin refers strictly to the apoenzyme, apoprotein (without bound retinal). When an opsin binds retinal to form a holoprotein, it is referred to as Retinylidene protein. However, the distinction is often ignored, and opsin may refer loosely to both (regardless of whether retinal is bound). Opsins are G-protein-coupled receptors (GPCRs) and must bind retinal — typically 11-cis retinal, 11-''cis''-retinal — in order to be photosensitive, since the retinal acts as the chromophore. When the Retinylidene protein absorbs a photon, the retinal isomerizes and is released by the opsin. The process that follows the isomerization and renewal of retinal is known as the visual cyc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photopsin
Vertebrate visual opsins are a subclass of ciliary opsins and mediate vision in vertebrates. They include the opsins in human rod and cone cells. They are often abbreviated to ''opsin'', as they were the first opsins discovered and are still the most widely studied opsins. Opsins Opsin refers strictly to the apoprotein (without bound retinal). When an opsin binds retinal to form a holoprotein, it is referred to as Retinylidene protein. However, the distinction is often ignored, and opsin may refer loosely to both (regardless of whether retinal is bound). Opsins are G-protein-coupled receptors (GPCRs) and must bind retinal — typically 11-''cis''-retinal — in order to be photosensitive, since the retinal acts as the chromophore. When the Retinylidene protein absorbs a photon, the retinal isomerizes and is released by the opsin. The process that follows the isomerization and renewal of retinal is known as the visual cycle. Free 11-''cis''-retinal is photosensitiv ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Visual Phototransduction
Visual phototransduction is the sensory transduction process of the visual system by which light is detected by photoreceptor cells ( rods and cones) in the vertebrate retina. A photon is absorbed by a retinal chromophore (each bound to an opsin), which initiates a signal cascade through several intermediate cells, then through the retinal ganglion cells (RGCs) comprising the optic nerve. Overview Light enters the eye, passes through the optical media, then the inner neural layers of the retina before finally reaching the photoreceptor cells in the outer layer of the retina. The light may be absorbed by a chromophore bound to an opsin, which photoisomerizes the chromophore, initiating both the visual cycle, which "resets" the chromophore, and the phototransduction cascade, which transmits the visual signal to the brain. The cascade begins with graded polarisation (an analog signal) of the excited photoreceptor cell, as its membrane potential increases from a resting po ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Light
Light, visible light, or visible radiation is electromagnetic radiation that can be visual perception, perceived by the human eye. Visible light spans the visible spectrum and is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequency, frequencies of 750–420 terahertz (unit), terahertz. The visible band sits adjacent to the infrared (with longer wavelengths and lower frequencies) and the ultraviolet (with shorter wavelengths and higher frequencies), called collectively ''optical radiation''. In physics, the term "light" may refer more broadly to electromagnetic radiation of any wavelength, whether visible or not. In this sense, gamma rays, X-rays, microwaves and radio waves are also light. The primary properties of light are intensity (physics), intensity, propagation direction, frequency or wavelength spectrum, and polarization (waves), polarization. Its speed of light, speed in vacuum, , is one of the fundamental physi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
