[TML] Alien ecologies

[Jerry W Barrington]

On 8/29/08 3:56 PM, "Bruce Johnson" <johnson at pharmacy.arizona.edu> wrote:

> That's because the absorbtion peak does not depend on the protein
> (which can change via evolution) but the captive metal atoms chemistry
> (which cannot)

Hmm.  Chlorophyll a, b, c1, c2, and d all have Mg at the center.  Yet they
have different peaks.  So apparently the proteins *do* matter.

And: "Chlorophyll is a chlorin pigment, which is structurally similar to and
produced through the same metabolic pathway as other porphyrin pigments such
as heme."  Heme contains iron instead of magnesium.  Since they are both
produced by the same pathway, it appears evolution *can* change what metal
is in there.  Further, related molecules use cobalt, nickel, or even no
metal.

Also, many organisms use multiple pigments in combination, in order to
*have* a broader absorption spectrum.