Feb 25, 2006

something in the water

Chirality--the "handedness" of amino acids--has been trumpeted by creationists for some time as "not just a major problem... but a dilemma" for origin of life theories. As Charles McCombs writes,
Chirality is probably one of the best scientific evidences we have against random chance evolution and chirality totally destroys the claim that life came from chemicals. Obviously, this is one fact they do not even want to discuss.... the process that forms chirality cannot be explained by natural science in any amount of time [emphasis added].
This naysaying is quite strange given the ongoing research in the field--AIG, a rival creationist site, lists ten (!) previous theoretical explanations and their various shortcomings--and even stranger, given that chirality may have an explanation after all.
All amino acids found in living organisms have left-handed chirality, even though left- and right-handed amino acids should chemically be the same. Meir Shinitzky and colleagues at the Weizmann Institute of Science believe the humble water molecule to be responsible.

Shinitzky dissolved polymers of left- and right-handed amino acids in water, and measured the pH at which they denatured from helices to random coils. This was 0.2 to 0.3 units higher for the right-handed molecules, which implied they were less stable. The effect disappeared when heavy water (D2O) was used.
The problem isn't yet solved to everyone's satisfaction, but at least demonstrates that saying "Science will never / can never" is often a bet against the odds.



(Note: For some odd reason NewScientist made their reportage available to subscribers only; weird, considering it's easily found elsewhere.)

1 comment:

Anonymous said...

Well, not all amino acids found in living organisms have left-handed chirality, because glycine doesn't possess a center of asymmetry at the alpha carbon atom :) Nice post, thanks. I didn't know that chirality is also a point in discussion on the origin of life.

Ola