On Sunday, I was alerted by a clamorous murder to the trouble: two maimed and bleeding Crows whom I captured and promptly delivered to Project Wildlife. One did not open the right eye and had an open sore near the left hallux, in addition to a wounded wing . Suffering was evident, and at best, I hoped for humane death. The other was active and vocal but grounded by wing injury and in the sights of a cat. An administrative assistant at Project Wildlife notified me yesterday that the latter Crow survived and is being nursed for re-release, while the former did not make it.
A few weeks ago, I was sort of a "first responder" to a guy I found lying unconscious on the curb. After the guy regained partial consciousness, the paramedics interrogated him as would law enforcement officers rather than like healthcare professionals and promptly shooed me away. It was at that moment when I was thinking that it would be nice to receive a courtesy update on the status of the patient . . . well, it is for the birds, at least!
In any case, I was very grateful to rely on Project Wildlife this time both for the mannerly intake and follow-up!
Why are egg yolks yellow? They contain two very similar yellow chemicals called lutein and zeaxanthin. You can see lutein here under the egg. I like this molecule because it's almost but not quite symmetrical!
These chemicals are synthesized only by plants. They're called xanthophylls, from the Greek words for 'yellow' and 'leaf'. You can get lots of xanthophylls from green leafy vegetables like spinach. Plants use use xanthophylls to deal with problems that arise when it's too sunny. Bright sunlight makes a lot of triplet chlorophyll, an excited form of chlorophyll, which can cause chemical reactions that damage the plant. The xanthophyll cycle is a way of removing excess energy from triplet chlorophyll in a harmless way.
Animals get lutein and zeaxanthin from plants. The retina of your eye contains these chemicals! Since these chemicals look yellow, they absorb purple light... and it seems they help our eyes avoid the damaging effects of that light.
Why do egg yolks contain these chemicals? I don't know.
These chemicals are colorful because they have a long chain of conjugated double bonds between carbon atoms - shown as alternating single and double bonds in this picture. Electrons vibrate back and forth along this chain in a fun quantum way. So, when a photon of the right color hits the molecule, it can easily be absorbed - and its energy goes into the motion of electrons!
Like piano strings, the electrons in chains of conjugated double bonds vibrate faster when the chains are shorter. Molecules with a chain of fewer than 8 such bonds absorb only ultraviolet light, so they look colorless to us. With every extra double bond, the system absorbs photons of longer wavelength. Lutein and xanthophyll absorb purple light - so they look yellow. Carotene, from carrots, absorbs blue light - so it looks orange!
For more fun, try:
See how similar they are! For the xanthophyll cycle, see:
For conjugated double bonds and how they absorb light, see:
And for those of you who might have seen the allegations of Blackwater in Donets'k (despite my Tweet-attempt to intercept the Daily Mail reporter who took the bait and shouted 'Blackwater!' in a crowded geopolitical community), I have compiled a quick and dirty list of why these claims are specious at best: goo.gl/yMVc0h
- Cymer, Inc.Sr. Scientist, 2012 - present
- Zoological Society of San DiegoIndependent consultant, 2010 - 2010
- University of California, San Diegopresent
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