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| History of the Rhodopsin Molecule
in the Eye  From the beginning of time, humans have tried to explain the complex process of vision. Recorded studies of human vision dated back at start to the time of Aristotle, who explained the process as a located object, altering the ‘medium’ (not known at the time, to be air) and being propagated by the eye. During the middle-ages, Aristotle’s theory was reversed to the popular theory of that time, which suggested that the viewer’s eye sent out emissions to the object and that those emissions enabled vision to occur. It wasn’t until 1210 A.D., when The Book of Optics, published by an Iraqi Muslim scientist, Ibn Alhaytham, initiated a scientific revolution and laid the foundation of modern optics. The book argued two major theories on vision; that we cannot see by rays being emitted from the object, or through physical forms entering the eye. In 1514-1564, Andreas Vesuvius carried out one of the first systematic studies of human anatomy and realized that vision is a complicated process that requires both the eye and the brain working together. And that the first step of this fascinating sense is carried out in the retina of the eye which contains photoreceptors that collect light and send signals to a network of neurons that then generate electrical impulses that go to the brain. Of the many photoreceptors in the eye is one characteristic to the vertebrate eye called Rhodopsin.  Ibin-Al_Haithem
One hundred years have passed since Frank Boll and Willy Kuhne first characterized rhodopsin and discovered the visual pigment cycle.
Rhodopsin, also known as visual purple, is the light sensitive pigment found in vertebrate rod cells of the retina. Rhodopsin consists of protein components called opsin, linked to non protein chromophores, called retinal. Retinal is a derivative of Vitamin A, which was discovered by George Wald in 1932, making our understanding of these visual proteins quite novel. Wald shared a Nobel Prize for his discovery of retinal structures in 1967. It is these retinal structures, which absorb the light and change forms to separate from the opsin component. This separation initiates the transmission of a nerve impulse to the brain, allowing distinction of light and dark. So our understanding of the vision process is quite recent. In 1972 transient absorption spectroscopy had shown that the first step in vision took less than 6ps. In 1991 Mathies et.all. Demonstrated that it occurs in 200fs (femtosecond is 10-15s.), one of the fastest photochemical reactions ever studied. The following section will provide a description of the eye and the protein Rhodopsin and other pigments that helps us see in the dark. Rhodopsin Structure of the Eye What is Rhodopsin Spectroscopy Studies of Rhodopsin Lesson plan References | |
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