George Wald - The discoverer of vit-A role in retina - WorldOfChemicals

George Wald – discoverer of function of vit-A role in retina

George Wald - An American Scientist

Biography & contributions

George Wald was an American scientist and Nobel laureate born in New York City on November 18, 1906 - died on April 12, 1997. He shared the 1967 Nobel Prize in Physiology or Medicine with Haldan Keffer Hartline and Ragnar Granit. Wald was also the winner of Eli Lilly Award for Fundamental Research in Biochemistry from the American Chemical Society in the year of 1939, Proctor Medal of the Association for Research in Ophthalmology in the year of 1939, Rumford Medal by the American Academy of Arts and Sciences in the year of 1959. In 1966 he was awarded the Ives Medal of the Optical Society of America.

In the 1950s, Wald and his colleagues used chemical methods to extract pigments from the retina. Then, using a spectrophotometer, they were able to measure the light absorbance of the pigments.

Research Methodology

George Wald was the discoverer of vitamin A as a component in eye retina. He demonstrated that when rhodopsin is exposed to sunlight it will release opsin protein and vitamin-A containing compound.

This discovery had led to the giving importance of vitamin A role in retina function. He continued this research and found a pigment called rhodopsin in the rods [rod cells are the basic cells of retina].

Wald found that rhodopsin was composed of a colorless protein called opsin and a yellow substance called retinene - it is form of vitamin A. When stimulated by light, the rhodopsin molecule breaks down into its two parts, and the retinene becomes vitamin A. Darkness can reverses the retinene to rhodopsin conversion process.

These biochemical changes trigger electrical activity that stimulates the retinal and optic nerves, resulting in vision. His further research demonstrated that pigments in the retina's cones, also related to vitamin A. Retina’s cones are mainly responsible for color vision and in absence of these cells may lead to color blindness.

Facts about pigments

Pigments are a class of chemical compounds that can be organic or inorganic. Pigments are insoluble and are applied not as solutions but as finely ground solid particles mixed with a liquid. In general, the same pigments are employed in oil- and water-based paints, printing inks, and plastics. Pigments may be organic (i.e., contain carbon) or inorganic. Organic pigments made from natural sources have been used for centuries, but most pigments used today are either inorganic or synthetic organic ones. Synthetic organic pigments are derived from coal tars and other petrochemicals. Inorganic pigments are made by relatively simple chemical reactions or are found naturally as earths.

Carbon black, used to give black colour to printing inks. Iron-oxide earth pigments yield ochres (yellow-browns), siennas (orange-browns), and umbers (browns). Certain compounds of chromium are used to provide chrome yellows, oranges, and greens, while various compounds of cadmium yield brilliant yellows, oranges, and reds. Iron, or Prussian, blue and ultramarine blue are the most widely used blue pigments and are both inorganic in origin. Organic pigments include azo pigments, which contain a nitrogen group; they account for most of the organic red, orange, and yellow pigments. Copper phthalocyanines provide brilliant, strong blues and greens that are unusually colourfast for organic colours.

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