Aucbvax.1505
fa.human-nets
utzoo!duke!decvax!ucbvax!DERWAY@MIT-ML
Wed Jun 3 00:42:46 1981
HUMAN-NETS Digest V3 #111
HUMAN-NETS AM Digest Wednesday, 3 Jun 1981 Volume 3 : Issue 111
Today's Topics:
Administrivia - Content of Human-Nets,
Left Handed Sugar - Isomer Chemistry
& Heavy Water Biology & Reversing Matter
----------------------------------------------------------------------
Date: 06/03/81 00:49:19
From: The Moderator <DERWAY@MIT-AI>
Subject: Submissions to Human-Nets
Increasingly, Human-Nets has become a broader and broader
discussion, until now there are clearly people that view the list as
a place to discuss whatever happens to be on their mind. To a certain
extent, this may be due to the age of the list. Perhaps we have
discussed so much of the area directly related to our supposed
subject, that it is difficult to find new ideas in those areas.
I have been receiving complaints recently, about the
randomness of the topics discussed in Human-Nets. Consider,
(especially just before you send that message!), that over 3,000
people will be reading it. Does it really have anything to say? Roger
Duffey established the policy of never rejecting a message that wasn't
in some way out and out objectionable. Since then, the list has grown,
and the incidence of submitted messages, which say nothing of
interest, EVEN ON THE TOPIC THEY PURPORT TO DISCUSS, has grown
sharply. The combination of the breadth of the discussion, and the
high ratio of nonsense to informative, interesting messages, is
causing a real problem in that they grossly slow down the exchanges,
and annoy a good many people, particularly those with slow terminals.
Please think a little longer before sending in an off-the-cuff
comment, or a message that really doesn't make any point.
I should never have allowed the left handed sugar discussion
to take place. I first published the reprint of the news article
because someone had sent it in, it wasn't objectionable, and I even
thought there might be a fairly wide interest in it. Unfortunately,
the latter was all too true. I really had not thought that a
discussion was appropriate over the list. However, all of these people
worked hard on the messages, so here they are. Please, keep further
discussion among yourselves, as it really has no relevance to
Human-Nets. Thankyou,
Don
------------------------------
Date: 21 May 1981 04:36 edt
From: JSLove at MIT-Multics (J. Spencer Love)
Subject: Re: Jerry Leichter's message on sugars
Your memory of chemistry is faulty. There are LOTS of ways to hang 6
water molecules worth of atoms on 6 carbons; these are called isomers.
Glucose (also called dextrose), fructose (also called levulose) and
mannose are just three; there are many others. Those three are all
"right handed" sugars; none are mirror images of each other. My CRC
gives fucose as a left-handed sugar; where it occurs I don't know.
Then there are the 12-carbon sugars, of which sucrose, maltose, and
lactose are examples. And 18-carbon sugars like raffinose. Sucrose
is glucose + fructose - H2O, while maltose appears to be glucose +
glucose - H2O. Unfortunately, this is an oversimplification: my CRC
gives alpha and beta forms for glucose, with slightly different
characteristics.
Lactose is a 12-carbon sugar that can be found in milk and that some
people lack the enzyme to digest. Actually, most people lose it when
milk stops being a significant component of their diet, but lacking it
is much more critical at age 3 weeks. I don't know if it is a
component in milk allergies, but if it is, then it would be an example
of a toxic sugar isomer. It would be nice to know whether any mirror
image sugars (of nontoxic sugars) are toxic; I expect we will find out
soon.
As I remember it (my term to go out on a limb), we can only metabolize
(that is, make ATP using) one sugar isomer: dextro-glucose (by various
pathways), so to utilize another sugar we must have an enzyme to mung
it into one or more glucose molecules. That is why fructose is said
to be better for you; the conversion acts as a bottleneck and causes
the glucose to be released into your system more gradually, which is
less of a shock to the regulatory mechanisms. Of course, any isomer
that we lack the enzyme to convert is just so much bulk (like adding
cellulose to food). This difference is more subtle than simple
"sugarness", so it isn't surprising that levulo-glucose can't be
converted. At least it's safer than eating antimatter...
How are calorie counts calculated for such foods? The energy is there
but inaccessible. For some foods I have read that simple burning will
suffice, measuring the heat produced, but this fails when much
cellulose is present, and indigestible sugars will make it worse. Are
there microorganisms that are cultured for this purpose that have
similar digestive capabilities to homo sapiens?
I have read of an amino acid combination that tastes sweet, although
you can't heat it up much or it denatures. It seems the critical
thing is some bond angles on the sugar, which any compound might
duplicate. So it seems quite plausible that the mirror image of
glucose would taste identical to glucose; same for sucrose.
Would some PRACTICING biochemist like to set the record straight by
typing in a list of six and twelve carbon sugars, the breakdown of the
more complex ones,and their handednesses (if different from the
right-handedness that has been repeatedly mentioned in this forum for
glucose)? Toxicity and sweetness levels would be nice, too, but I
guess that diagrams showing exactly how all the isomers differ would
be too much to ask (tho you could include a reference, a CRC is pretty
useless for this). Thanks...
------------------------------
Date: 28 May 1981 2005-EDT (Thursday)
From: Mark.Sherman at CMU-10A
Subject: Left vs. Right Handed Substances
During the sugar discussions, I got the impression that some people
were not convinced that different stereochemistries of a substance
could have different effects in the body. According to the Wasacz in
the latest copy of American Scientist, morphine comes in both left
handed (levorotatory) and right handed (dextrorotatory) forms, but
only left handed morphine is analgesic and addicting.
-Mark
------------------------------
Date: 28 May 1981 (Thursday) 0754-EST
From: RUBENSTEIN at HARV-10
Subject: Heavy Water and isomers
Since deuterium is heavier than normal hydrogen, reactions involving
it are slower when the hydrogen is involved in the rate limiting step.
Certain enzymatic reactions are slowed considerably when run in heavy
water; the example that comes to mind is the family of sugar
isomerases which are slowed by something like 45%. The net effect of
all this, if I remember correctly, is a horrible, retching death after
12 to 16 hours, with LD50 around 150 or 200 ml for adults. I don't
have a Merck Index handy, but that's what I remember.
As to mirrors, would your mirror change a positive to a negative
charge? No? Then don't worry about that anti-matter explosion. The
difference between matter and anti-matter is more than handedness.
The spin would reverse, but most stable systems consist of pairs of
electrons with opposite spin. Likewise for nuclear spin (unless
you're in a magnetic field of the tens of kilogauss variety).
Hope this clears up a few misunderstandings.
Stew
Btw, heavy water always struck me as a really neat murder weapon. 200
mls isn't that expensive (about $80). Who ever heard of doing a mass
isotopic abundancy analysis during an autopsy?
------------------------------
Date: 28 May 1981 (Thursday) 1607-EST
From: RUBENSTEIN at HARV-10
Subject: Heavy Water and isomers
Upon checking my source, I have to admit that my memory of the lethal
dose of heavy water was based on an oft-repeated myth. According to
Merck Index, Heavy water is considered non-toxic, though it stunts the
growth of mammals on prolonged exposure, presumably due to the
slowdown of enzymatic reactions.
Too bad, I still think it would have made a great murder weapon.
Almost as good as the dagger made of ice.
Stew
------------------------------
Date: 05/28/81 08:08:22
From: TK@MIT-AI
Subject: Heavy Water
Deuterium oxide (heavy water) is poisonous, and will kill you when
consumed such that your total water intake is about 60% D2O. The bug
is apparently the rather subtle change in the hydrogen bonding, which
makes things like DNA work.
------------------------------
Date: 28 May 1981 06:11:15-PDT
From: decvax!duke!unc!smb at Berkeley via <CSVAX.UPSTILL BERKELEY AT>
Subject: sterioisomers
About Will Martin's query on deuterium: I'm a little skeptical that it
would have much effect, but it might. For one thing, biologists often
tag molecules with tritium, and I've never heard that this interferes
with their function. On the other hand, the ratio of O-16 to O-18 is
used as a clue to climate in the past, so there is SOME effect there.
Incidentally, not all science fiction writers have neglected the
anti-matter problem. The reversing machine in Zelazny's "Doorways in
the Sand" was described second n-axial inversion unit. It seems that
the first one lacked a "particle exceptor program"....
------------------------------
Date: 28 May 1981 11:26:42-EDT
From: cjh at CCA-UNIX (Chip Hitchcock)
Subject: chemistry and reversal
As an ex-chemist, my first remark about the alleged problems of
deuterated water (i.e., \\not// tritiated, which would be radioactive)
is that it's almost certainly nonsense. The problem is that the old
definition of isotopes as those forms of an element that were not
separable by chemical means is fading as the boundaries between
physics and chemistry are fading; the latest CHEMICAL & ENGINEERING
NEWS reports from the last national ACS meeting that someone has found
a reaction that behaves differently if several of the hydrogens are
replaced with tritium. Since this is still a relatively subtle
difference, I strongly doubt that it supports the idea that deuterated
water would not serve the same physiological functions as ordinary
water. Biochemical reactions are primarily a matter of sizes, shapes,
and relative concentrations, and the size, shape, and molecules/space
of heavy water are all \\very// close to those of ordinary water.
With regard to the proposed sugars, the first question is what
process is used; the FDA has standards for decaffeinated coffee, for
instance, because decaf is sometimes made by dissolving out the
caffeine from the beans with methylene chloride, which is \\not//
something you want to consume. Any process that would invert a normal
sugar would be fairly drastic chemically, so the same standards
against residuals would apply. Of equal concern is the effect of
another indigestible substance on the body; the low-bulk American
standard diet has disadvantages but a high-bulk diet is not without
problems either. (This is more of a concern for the plan to bind the
sugars to indigestible polymers.) Also, when I was doing some
research several years ago in producing a preponderance of one optical
isomer of a given amino acid, I remember being told that some of the
mirror images of necessary amino acids were known to be toxic; without
any preexisting information the FDA is right to be concerned about
this. If the manufacturing proposals were simply to sort out an
isomer from a mixture of sugars known to be tolerable, there wouldn't
be a problem; but I don't think that is the case.
------------------------------
Date: 28 May 1981 at 0842-PDT
Subject: Reversal Symmetry
From: zaumen.tscb at Sri-Unix
There is a technical error in Bruce Lucas's comment about
mirror images: the mirror-image of matter in not anti-matter because
anti-matter differs in other quantum numbers besides parity (such as
lepton number, baryon number, etc).
The confusion is over symmetries: Certain physical laws are
invarient under parity (mirror-imaging), others are invarient under
charge-reversal, and others under time-reversal. It turns out that
all of these seem to hold for the strong interactions (nuclear forces)
and all of these fail (individually) for the weak interactions.
Quantum field theory predicts (assuming only causality) that all
physical laws are invarient under the combination of all three
symmetries (CPT invarience). So far, CPT is the only one that works
in every known case, and if that fails, either relatavistic quantum
mechanics or causality is in serious trouble.
------------------------------
Date: 05/28/81 17:38:40
From: KWH@MIT-AI
Subject: Reversing atoms?
:flame
Huh? The mirror image of matter is antimatter? You're confusing
topological and physical terminology- The mirror image and fourth
dimensional twisting, and the handedness issue is all a part of
topology- Look at your right hand- and your left hand- and try to
transform them into each other. The difference between them is
topological, and you can't do it, by the same token that by twisting a
right-hand glove around, you can't fit it on your left hand. You can
flip a two-dimensional object from right to left handed, by just
flipping it over (Physically) But you can only flip a three
dimensional object over in a fourth spacial dimension- (You can also
flip a two dimensional object over, however, by running it over a
mobius strip, and if you jam yourself through a Klein bottle, you will
flip around)
But you still wouldn't be made of antimatter- Matter is RADIALLY
symmetric, with electrons around a positive nucleus, antimatter is
similar, but with postive particles around a negative nucleus, but in
either case, flipping gets you nowhere- How can you have a
"right-handed" ball? Flipping it does nothing.
However, there is a neat theory by Feynaman that proposes antimatter
is regular matter moving backwards in time... Maybe that's why we
don't have visitors from the future, they start up the time machine
and blow the earth and themselves to pieces.....
:unflame
<SORRY>
Ken Haase
------------------------------
Date: 29 May 1981 (Friday) 0324-EDT
From: SHRAGE at WHARTON-10 (Jeffrey Shrager)
Subject: ragus desrever
I suspect that this entire conversation belongs in SFL but... Firstly,
who says that sending someone thru a reversal machine will reverse
down to the subnuclear level? Did you build the machine? Do you have
any idea how it works? Maybe is has a LOOP UNTIL LEVEL=ATOMIC in it
someplace. Also, what would the result be if we went and reversed
even deeper than the anti-matter level? Can you reverse quarks? Can
you even reverse anything lower than a molecule in the isomeric sense
(probably not). At lower levels you're dealing with spins and
resultant charges rather than structure but I don't think that anyone
really knows what's what down there so maybe the structure of a proton
dictates the charge.
As to the FDA's legal rights and their interpretation of the law...
given half a chance, they'd outlaw distilled water!
------------------------------
End of HUMAN-NETS Digest
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