Re: OT Groceries on-line.

On Wed, 24 May 2006 08:00:44 +0100, "Siderius Nuncius"
<matron.nuncius@xxxxxxxxx> wrote:

<snip stuff about chirality>>

Well, I think it's interesting, so there. More stories about Pasteur,
tartaric acid and a pair of tweezers and about many organisms being very
fussy eaters when it comes to chirality are available on request, but I
suspect that this post has already delighted you long enough[1].

One of the organisms that's a very fussy eater when it comes to
chirality is man.

A few years ago, food scientists were experimenting with non-fattening
edible fats. This may sound like a contradiction on terms, but they
were looking for a fat that would look and taste like butter or
margarine, but would have virtually no calories.

The approach they came up with was to manufacture fats with the
opposite chirality to that found in natural butter and margarine.
They found that the enzymes that digest such foods couldn't handle the
molecules with a different chirality, so the fat didn't get digested
and didn't contribute any calories to the body's energy budget.

They did actually succeed in producing non-fattening butter, IIRC.
Unfortunately, there were some rather unpleasant side effects. The
lower bowel is not equipped to handle undigested fat (natural fats
never reach the lower bowel, having been digested higher up in the
gastric tract). The consequences of having undigested fat in the
lower bowel were not pleasant. I promise you, you don't want the
details.

BTW - anyone who's still reading this thread and hasn't yet lost the
will to live might be interested in this:

http://www.abc.net.au/rn/science/ss/stories/s432409.htm

Among other things, it points out that non-biological chemical
processes invariably produce equal amounts of right-handed and
left-handed molecules, whereas biological processes tend to produce a
preponderance of one chirality.

So, one of the ways in which we could identify whether life exists, or
has existed, on another planet, would be to analyse all the
optically-active molecules we find there and look for an assymetry
between right-handed and left-handed variants.



Tony Gardner
N.B. Return E-mail address is spamtrapped.
Replace "spambin" with "tony" and "nospam" with "gardner"
.

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