Re: Are dinosaurs really reptiles? (2)

[Martin Baeker <martin.baeker@tu-bs.de>]

On Mon, 28 Apr 2008, David Marjanovic wrote:

> > > They're soft.
> 
> That's not the difference. Mammalian claws/hooves/nails are also
> alpha-keratin.
> 

Just a minor note: AFAIK, in general beta-Keratin is stiffer (larger
young's modulus, about 5-8GPa, compared to 2-3GPa or so for
alpha-Keratin) than alpha-Keratin due to the beta-structure (if you
strain it, you strain the covalent bonds along the backbone chain of
the molecule, whereas in alpha-keratin you start by straining the
hydrogen bonds along the helix.)


                   Priv.-Doz. Dr. Martin BÃker
                   Institut fÃr Werkstoffe
                   Technische UniversitÃt Braunschweig
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