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[IP] sugar's handed-ness, and Thanks!

On Thu, 11 Jan 2001, Bonnie Richardson wrote:
> Subject: [IP] I got it!  
> Thank you, thank you.....I was trying to explain the Splenda stuff to
> someone and couldn't get it out!   GREAT EXPLANATION and I get it now!
> Thanks, Jim!
>  SNIP>>>>> Okay I gotta ask...about this 'left-handed' sugar stuff.  What
> does it mean 
> > when the sugar is 'left-handed'?  And is there 'right'handed'?
> Jim Said: 
> There are different directions in which some of the molecules twist in
> biological systems.  Most common in natural biological systems is left or
> alpha -- hence DNA is an alpha helix, that is it coils to the left, or
> counter clockwise.  If it coiled to the right, or clockwise, it would be a
> beta helix.  If I had to guess, if sucrose has a twist, then if a molecule
> twisted in the opposite direction, it would have a different effect on the
> tissue it encountered.
> Jim Hansfield<<<<<<SNIP

I don't think that this explanation is quite right.  While polymers like
DNA can be left- or right- handed helicies, a sugar's handed-ness refers
to the direction that plane polarized light is directed after encountering
crystals (or solutions) of the compound.  Organic compounds such as amino
acids and many sugars have what is known as chirality.  This means that
the compound is asymetric about one or more of its carbon atoms, and may
have two forms that are mirror images of each other. As noted in a
previous post, these forms are the D- or dextrorotatory (right-handed),
and the L- or levorotatory (left-handed) configurations. Crude ASCII
example follows:

  D-glucose       L-glucose

   H-C=O            H-C=O
     |                |
   H-C-OH          HO-C-H
     |                |
  HO-C-H            H-C-OH
     |                |
   H-C-OH          HO-C-H
     |                |
   H-C-OH          HO-C-H
     |                |
   H-C-H            H-C-H
     |                |
     OH               OH

Enzymes in the human body that use glucose (metabolize it) are specific
for D-glucose.  So, while the L-glucose still has a perceived sweetness,
our bodies are unable to use it for energy.

On another subject, I would like to thank the many folks who responded
with advise and comments on selecting a pump.  You were quite correct in
that the representitives are HAPPY to meet with you, permitting a full
hands-on comparison of the various models.  I have now seen all but the
dtron, and I'm presently leaning toward the Animas, dependent on my
insurance.  The PPO that I am on may have a contract with MiniMed.  The
508 was a very close second in my own personal preference so I would not
be dissapointed either way.  Thanks, again,

--Richard Seyler (type I, 21 yrs, pumping hopefully soon)
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