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Re: Feathers for S excretion
Interesting Reichholf translations. However, I think he needed some more
basic biochemistry before he got started.
H2S? I wasn't aware the body produced ANY H2S in metabolizing proteins.
That's really news to me (another way of saying I'm deeply skeptical that it
is a significant factor).
As far as an insect diet, 3% sulfur is not a great amount, in fact, it is
just slightly above typical levels among all known proteins. Don't forget, S
is a heavier atom than, say, carbon or nitrogen, so it's weight-percent is
exaggerated relative to its mole-percent. If insects contain only 3% S, then
they are not a particularly burdensome source of S after all. Reichholf's
basic datum seems weak.
The notion that feathers have a "special" sort of sulfur requirement is
flawed. The S, primarily as cystine, participates in crosslinking the
proteins of feathers to give them strength. Trouble is, ALL skin structures
have this same crosslinking. Feathers, hairs, scales and even just plain skin
ALL have S-linked crossbridges between their proteins. So there is no real
evolutionary novelty in the S content of feathers.
And, I'll reiterate my first statement that kidneys make short work of
even massive loads of S, no sweat. (Well, kidneys don't sweat, now do they?).
Thomas P. Hopp
Author of DINOSAUR WARS, a science fiction novel published by iUniverse
Now Humans are the Endangered Species! http://members.aol.com/dinosaurwars