The Verse - Volume 9
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Purple Particulars - Purple helps you see in the dark!

Purple Particulars continues its mission to bring you every bit of obscure purple-related knowledge possible. This installment is from the world of biology. Did you know that Purple helps you see in the dark? Rhodopsin, also known as visual purple, is a photoreceptor protein. It is a pigment of the retina, which is responsible for the perception of light.

Here’s the definition: Visual purple is a photochemical substance of a purplish red color, contained in the retina of human eyes and in the eyes of most animals. It is quickly bleached by light, passing through the colors, red, orange, and yellow, and then disappearing. Also called rhodopsin and vision purple.

Here’s the science: A so-called 7TM G-protein coupled receptor, each scotopsin protein binds as a cofactor a molecule of retinaldehyde, which derives from Vitamin A and is made in the retina. Isomerization of retinaldehyde by light induces a conformational change in rhodopsin and a biochemical cascade by way of the associated G protein. The rhodopsins encoded by different genes differ in the wavelengths of light which they absorb most strongly. This variation causes the cones of the retina to differ in their response and is the basis for color vision. The rhodopsin of the rods most strongly absorbs green-blue light, which is why it is some times called "visual purple" (it appears reddish-purple). Some bacteria express a related protein called bacteriorhodopsin to carry out bacterial photosynthesis.

Here’s the tie in with Versent, the purple guys: The next time you feel like you’re “in the dark” when it comes to technology, remember purple!