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Re: Stuff Of Life (was, "H.C. Urey's work")

Hello Robert,

Thank you for the article. It was not the one I was looking for, but I
think the article you provided here is better than the one I am looking for.

For those on the list who did not, or were unable to decode the attachment,
below is the article in full. If you have already read the article, then
proceed no further as there is nothing new.

Cheers,

Martin

Subject: Stuff Of Life
Author:  Ronald C Baalke at Gateway
Date:    9/10/98 8:41 AM
For JPL internal use only.
http://www.newscientist.com/usa/bayarea/stuffoflife.html

Stuff of life

When astronomers re-created outer
space here on Earth they were amazed to
find some of the key ingredients of life,
and even cell-like bubbles.
Gretel Schueller reports
IN THE near vacuum of interstellar space, temperatures hover just above
absolute zero, where even the wobbling of atoms grinds to a halt. Dotting
this empty, frigid world are huge globs of gas and dust grains, so numerous
they block out nearly all light. And outside the shelter of these
interstellar clouds, bombarding cosmic and ultraviolet rays slash most
molecules to shreds.

Millions  of light  years away,  under the  sunshine and  palm trees  of
Mountain View, California,  in a lab tucked  away in the  grounds of NASA's
Ames Research Center,  Lou Allamandola and  his  colleagues   have  been
recreating  that  world  of extremes.  And in  doing so,  they have
uncovered tantalising hints  that   life  may  have  emerged   not  from
some  warm primordial  slime on  Earth, but  on a dust  grain in  the icy
heart of space.
It's long been  suspected that comets made the Earth habitable by
delivering water  and gases,  and that  they perhaps  even provided  some
of the  simpler  chemical  building blocks  of life. But  what the NASA
Ames  team has found goes  far beyond that.  When they  recreate the  harsh
conditions  of space  in their  lab, not  only do  they generate
astonishingly complex organic  compounds similar  to those vital  for life
on Earth today,  but also  curious cell-like  structures that  may have
housed our planet's earliest life forms.
The  origin  of these  intriguing  findings is  coincidentally enough also
the birthplace of stars and  planets. With 10 000 atoms  per cubic
centimetre, interstellar  clouds of  gas and dust are sufficiently  dense
that individual blobs within them collapse   under  their  own   gravity,
forming   stars  and, eventually, swirling  systems of planets. (While
this density is crushing  by space standards, the air on  Earth is about 25
000  trillion times thicker.)  In space, the density  of these clouds  also
offers  another  advantage that  may have  helped generate life  on Earth.
Like people in  a crowded dance club, molecules  of gases, such  as
methane, carbon  monoxide, water vapour and ammonia,  are continuously
banging and bumping into dust  "seedlings"--grains  of   silicate  the
size  of  smoke particles that have been ejected from old stars.

While  most  astronomers   have  concentrated  on  the  gases, Allamandola
has always had  his eyes on  the grains.  Just as water  vapour molecules
rising  from bubbling soup will  hit a cold kitchen window  on a frosty
night, stick and freeze, says Allamandola,   the  same   thing  happens
on  the   silicate seedlings. When gas  molecules smash into the cold
grains they stick,  creating  an   icy  skin  of  frozen  gases.  Infrared
telescopes  first  detected  the  gas particles  and  silicate grains  in
the 1970s.  But no detection  device was, or  is to this day,  powerful
enough to see how  they interact in space. So  Allamandola,  who trained
as  a  cryogenics chemist,  and physicist   Mayo  Greenberg  of   Leiden
University   in  the Netherlands,   set  out  to   do  what  most   people
thought impossible: build bits of interstellar space here on Earth.

Nowadays, a  deafening buzz permeates Allamandola's  lab. It's the sound
of cryocoolers--high-powered refrigerators--keeping the simulated
interstellar clouds at a  cool 10 degrees above absolute   zero.  The
"clouds"  are   actually  vacuum-sealed chambers the  size of shoe boxes. A
gaseous mixture of water, methane,  ammonia and  carbon monoxide  flows
through  a metal tube into  each chamber, freezing onto what  in the lab
counts as  a dust  grain--a few  square centimetres  of aluminium  or
caesium  iodide. As the molecules  pile up and freeze,  a thin white layer
of ice forms.
And  since  grains   in  space  receive  occasional  doses  of ultraviolet
light from  stars,  the simulated  grain and  its accumulated   chemicals
are   also   bathed  in   ultraviolet radiation.  Each hour of radiation
in the lab is  reckoned to equal  what  a grain  in  space would  receive
in a  thousand years, a mere  blip in the Universe's 15-billion-year
history. But that's enough  to get the action started. As soon as those
rays  hit  the molecules  on the  grain,  they start  breaking chemical
bonds, producing  highly reactive  radicals such  as +OH  and +NH2. The
icy temperatures provide the  ideal mixer. Frozen  to the spot,  the
radicals are  forced to  rejoin with their neighbours  in ways that would
never  occur if they were still  part of a  gas free to  fly off and join
more suitable partners.  The  result  is  a  profusion of  complex,
organic compounds.
The  work, however,  is a  little like  cooking with  a recipe that doesn't
tell you what the dish  will be. Allamandola and his  colleagues   know
what  they  start   out  with--simple, water-soluble gases--but analysing
the chemically complex end result is  trickier. Their latest chamber  is
fitted with both a  mass  spectrometer   and  an  infrared  spectrometer
which together give a  rough idea of the type of molecules that form on the
simulated dust grain. So  far, the NASA Ames  team has found  a  slew of
alcohols,  ketones,  aldehydes, alkanes,  a giant  molecule  called
hexamethylenetetramine  or  HMT,  and other  organic  molecules, some  with
as  many as  40  carbon bonds.   But   apart   from   that   broadbrush
description, Allamandola and his  team have yet to put names on most of the
chemicals  they   have  created  in  this   simulation  of  an interstellar
cloud.

When  biologist David Deamer  of the University  of California in  Santa
Cruz heard what  was going on at  the astrochemistry lab  at  Ames, he  was
soon  knocking  at Allamandola's  door. Deamer  had  been  studying  the
Murchison  meteorite,  which landed  in  Australia in  1969  and  has since
kept  numerous researchers  busy  identifying   its  rich  array  of
organic molecules. Deamer  had found something intriguing  deep within the
loose  sandstone-like  rock:  hundreds   of  microscopic globules. Grinding
the  stone into powder and flushing it with a solvent to  rinse out organic
molecules revealed what looked like  tiny two-layered vesicles  swimming in
the  liquid. When he published  his findings in Nature in 1985  (vol 317, p
792) it  caused a considerable fuss,  not least because no  one had any
idea what  these vesicles were, nor what sort of chemistry created them,
and where.
Deamer  suspected that clues  to his "fossil" vesicles  lay in the  residue
in Allamandola's  space chambers. After  all, the Murchison  meteorite is
believed  to be a  remnant of  a spent comet, and comets  are little more
than billions of ice grains piled  together in mountain-sized  chunks. When
Deamer warmed the  chamber residue  in water  and peered  at it  through
the microscope  he discovered tiny  droplets, each between  10 and 40
micrometres across,  up to  the size  of red  blood cells. Their similarity
with the Murchison droplets  was a sure sign that the  meteorite vesicles
had had their  origins far off in space,  not here  on Earth.  Deamer also
discovered that  the vesicles   fluoresced  under   ultraviolet  light,
one  more indication that they were made of complex organic molecules.
"It  was   a  remarkable  transformation  of   a  few  simple,
water-soluble  chemicals," says  Allamandola.  "It would  have been
considered science fiction  a few years before."  It was time to call in a
biochemist.
Last year, Jason  Dworkin, who had worked with Stanley Miller, famous for
creating  amino acids in the 1950s with little more than a  spark of
electricity and  a few hot gases,  joined the group.

A closer look

After  ruling out contamination,  Dworkin has been  working on creating
enough of  the dust grain ice to get a closer look at the  molecules  that
make  up the  vesicles.  It's an  onerous task. Running  the space chamber
for weeks  on end yields only about a  milligram of organic residue.  And
it contains dozens of  different chemicals. Still,  so far he has  created
enough residue  to show  that the  molecules that  make up  the outer layer
of the  vesicles behave like lipids, which are the major component of cell
membranes.
Just like soap  molecules, one end of each vesicle molecule is attracted
to water, while  the other end  avoids it  like the plague.  This  allows
the  molecules  to  self-organise  into spheres,   sticking  their
water-loving  heads   towards  the outside,  and  keeping their
water-hating  tails tucked  away inside.
Even  mainstream  research  into  the  origin of  life,  which relies  on
mixing chemicals  under conditions thought  to have existed  at the start
of  the Earth's history, hasn't  had any success  in  making  lipids  or
lipid-like  structures,  says Dworkin. Now Dworkin  plans to find out
whether the lipid-like molecules from the  space chamber can form bilayers
similar to the membranes of all modern Earthly cells.
But why  get so excited about  what looks at best  like a very rudimentary
membrane  that  just   happens  to   glow  under ultraviolet  light? Put
simply, the  finding matters  because many experts  believe that life, or
at least life as  we know it today, could  not exist without boundaries,
especially on a waterlogged planet like  our own ("Life is...", New
Scientist, 13 June, p 38).
Without  barriers, goes  one argument,  biologically important molecules
would  be so diluted in the  ocean that no chemistry could  ever happen.
Modern cell membranes,  with the  help of proteins embedded  in them, also
act  like a home-security and climate-control  system  all rolled  in  one,
regulating  what leaves and  enters, maintaining the correct  pH, and
providing a  means  of separating  charges  so that  the  cell can,  for
example,  create the  energy-carrying molecule  ATP. Membranes may   even
be   essential  for   stabilising  peptides,   the precursors of proteins.

A crazy idea

"The  [Dworkin] results  are very  exciting," says  geneticist and
astrophysicist  Pascale   Ehrenfreund   of  the   Leiden Observatory  in
the  Netherlands,  who  studies the  role  of interstellar  ice  grains in
the  origin  of life.  "Membrane formation  is a  crucial  step in  the
first  forms of  life." Earth's  first life  forms would  probably have
been far  too simple  to make  their own  membranes. But  whether they
were forced  to  make  use  of  ready-made  reaction  chambers,  or whether
they were merely  strands of nucleic  acids wriggling their way unprotected
through the primordial sludge (sticking to  a clay  surface or  happening
upon  a drying  puddle could have concentrated the  chemicals) is an open
question. If they did  need  to seek  shelter,  the Deamer-Allamandola
vesicles could be just the thing.
"If you can  form bubbles," says Tom Wdowiak, an astronomer at the
University of  Alabama  in Birmingham,  "then you've  got something  that
can serve  as a capsule." But  the Allamandola team  has done  more than
recreate what  might have  been our planet's  first  mobile   homes.  Their
reenactment  of  what happens  in an  interstellar cloud has  also shown
that space can  generate the right  sorts of life-giving chemicals  to go
inside.  In one  experiment, Allamandola  and Bernstein  added water  to
the  giant  HMT  molecules  created  in  the  space chamber,   yielding
formaldehyde,  ammonia  and   even  small amounts of amino acids.
More  recently,  the  NASA  Ames  team  turned  to  polycyclic aromatic
hydrocarbons, the  largest reservoir of carbon in the universe. Carbon  is
an essential part of  all known life, and PAHs  spewed out  by  the sloppy
combustion of  stars in  the process of  being born, contain between 10 and
20 per cent of all  the carbon in the  Universe. And although PAHs  are
never seen  in normal, healthy  cells, they are  highly biologically
active--for  example,  PAHs  in  soot  from  car  engines  and factories
are  carcinogenic simply  because  they can  wiggle their way into DNA.
The NASA Ames  team decided to use their space chamber to find out  what
might be  happening  to the  PAHs  deep within  the interstellar clouds.
The result was totally  unexpected. When they  fired gaseous  water and
PAHs such  as naphthalene  and anthracene one at  a time on to the
simulated "dust grains" in the space chamber,  and bombarded the mixture
with ultraviolet light,  it  produced  compounds  uncannily  similar  to
those needed for  life on Earth. "It's the UV  light that makes PAHs useful
[for life],"  says team member Scott Sandford. The rays broke the  water
molecules apart, and  the separated hydrogens and oxygens--locked in place
by the cold temperatures--reattached  themselves to  the  PAH, creating  a
huge array of complex chemicals.
"This change  is antithetical to what  everyone thought," says Wdowiak.
"Everyone thought  that PAHs  would just  break down [when  exposed to UV
light]. This is  great. We  didn't think PAHs  would turn  into anything
of use.  And suddenly  we had this huge reservoir  of carbon we never
thought about before."
Just this  July, space-in-a-lab simulations by  NASA Ames team member  Max
Bernstein produced  compounds called  quinones and alkaloids  from  PAHs.
(It  is  far  easier  to  analyse  the irradiated  PAHs,   than  the
residue  made   from  squirting methane,  carbon monoxide, water  vapour
and ammonia  into the space chambers.) Alkaloids  are ubiquitous in the
plant world. Meanwhile, quinones help  all cells move electrons around, are
crucial for  photosynthesis in plants and  are broken down for energy  in
human muscle  and brain cells.  The NASA  Ames team "is showing  that
carbon [from space] is coming  in, in a form that  is rich,  that can  be
utilised  by life,"  says chemist Richard Zare of Stanford University in
Palo Alto.
Bernstein  speculates that interstellar quinones  raining down on Earth
provided  a tasty treat for early organisms until, at some  point,  the
primordial  forerunner  of the  plant  took advantage   of   the  quinones
to   harness  sunlight.   But Allamandola  envisages  a  more  radical
scenario.  Sure,  the compounds  raining down on  Earth in cometary dust
could have provided a nutritious  meal for struggling primordial life, he
says.  But what of  those vesicles? Is it  possible--and this, Allamandola
knows,  "is  a  crazy  idea"--that they  and  the complex  organic
molecules  jump-started life  before reaching Earth?
Consider the  inside of a comet, he  says. There, under layers of  icy
material,  molecules  created  by  ultraviolet  light falling  on  PAHs and
other gases  stuck  to silicate  grains would be shielded  from the worse
radiation. Perhaps the comet swoops  by a  star, warming  the outside  just
enough  to melt some ice, providing  water for the cell-like vesicles to
form, just  as they  did  when Deamer  thawed the  residue from  the space
chamber.
Whizzing through  space in the belly of  the comet wouldn't be a  smooth
ride.  Gradually, the  amino acids,  PAHs and  other organics would jiggle
their way into the vesicles. And voil_, you'd  have  reaction   chambers
chock-a-block  with  complex organic  molecules primed  to generate  the
very  first cells. "Maybe  they're just  sitting there  waiting like  seeds
in  a packet to hit  the right place," he says. Allamandola's "crazy idea"
could  be  checked  out  early next  century  when  the European  Space
Agency's  International  Rosetta  Mission  is scheduled  to  drill into  a
comet's  core and  brings  whole pieces back to Earth.

"It's  a big  stretch from  making vesicles  and encapsulating organic
compounds to  promoting  life," says  John Cronin,  a prebiotic chemist at
Arizona State University in Tempe. "It's hard to  imagine how that can take
you  to anything as complex as a  nucleic acid that can  store and
reproduce information." But, he adds,  "it's hard to imagine that process
anywhere, so maybe it's not such a big step."

Now,  Bernstein  and Allamandola  plan to  mix  PAHs in  their space
chamber with  all the  gases found  in an  interstellar cloud--water,  plus
methane,  ammonia  and  carbon  monoxide. "It's  going to be like  the Wild
West. Anything  can happen," says Allamandola.

"Anything  can  happen"   could  be  space's  new  motto.  The
space-chamber  shows  that  under  extreme  conditions  simple organic
ingredients can  produce a rich banquet of potentially life-spawning
chemicals far  more easily than anyone expected. In short, it could happen
just about anywhere.

"The  most  amazing thing  is  that  we start  with  something really
simple. And then  suddenly we're making  this enormous range  of complex
molecules," says  Allamandola. "When  I see this  kind  of  complexity
forming  under  these  exceedingly extreme conditions,  I begin to really
believe  that life is a cosmic imperative."

Gretel Schueller is assistant editor at Audubon magazine in New York
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