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New Hypothesis For Origin of Life Proposed (Forwarded)



 
 
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Old December 5th 07, 07:41 AM posted to sci.astro
Andrew Yee
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Default New Hypothesis For Origin of Life Proposed (Forwarded)

University of California-Santa Barbara

CONTACT:
Gail Gallessich, 805-893-7220

FEATURED RESEARCHERS:
Helen Hansma, 805-729-2119

December 4, 2007

New Hypothesis For Origin of Life Proposed

Life may have begun in the protected spaces inside of layers of the
mineral mica, in ancient oceans, according to a new hypothesis.

The hypothesis was developed by Helen Hansma, a research scientist with
the University of California, Santa Barbara and a program director at the
National Science Foundation. Hansma presented her findings at a press
briefing at the annual meeting of the American Society for Cell Biology in
Washington, D.C.

The Hansma mica hypothesis proposes that the narrow confined spaces
between the thin layers of mica could have provided exactly the right
conditions for the rise of the first biomolecules -- effectively creating
cells without membranes. The separation of the layers would have also
provided the isolation needed for Darwinian evolution.

"Some think that the first biomolecules were simple proteins, some think
they were RNA, or ribonucleic acid," said Hansma. "Both proteins and RNA
could have formed in between the mica sheets."

RNA plays an important part in translating the genetic code, and is
composed of nitrogenous bases, sugar, and phosphates. RNA and many
proteins and lipids in our cells have negative charges like mica. RNA's
phosphate groups are spaced one half nanometer apart, just like the
negative charges on mica.

Mica layers are held together by potassium. The concentration of potassium
inside the mica is very similar to the concentration of potassium in our
cells. And the seawater that bathed the mica is rich in sodium, just like
our blood.

The heating and cooling of the day to night cycle would have caused the
mica sheets to move up and down, and waves would have provided a
mechanical energy source as well, according to the new model. Both forms
of movement would have caused the forming and breaking of chemical bonds
necessary for the earliest biochemistry.

Thus the mica layers could have provided the support, shelter, and an
energy source for the development of precellular life, while leaving
artifacts in the structure of living things today.

Besides providing a more plausible hypothesis than the prebiotic oceanic
"soup" model, Hansma said her new hypothesis also explains more than the
so-called "pizza" hypothesis. That model proposes that biomolecules
originated on the surfaces of minerals from the Earth's crust. The "pizza"
hypothesis cannot explain how the earliest biomolecules obtained the right
amount of water to form stable biopolymers.

A biophysicist, Hansma has worked with mica for decades beginning with her
work in biological Atomic Force Microscopy (AFM) in the late 1980s. "We
put our samples on mica, because it is so atomically flat, so flat that we
can see even bare DNA molecules as little ridges on the mica surface,"
said Hansma. "The layered mineral is made of sheets so thin (one
nanometer) that there are a million of them in a millimeter-thick sheet of
mica."

Hansma came upon her idea one day last spring when she was splitting some
mica under her dissecting microscope. She had collected the specimens in a
mica mine in Connecticut. The mica was covered with organic material. "As
I was looking at the organic crud on the mica, it occurred to me that this
would be a good place for life to originate -- between these sheets that
can move up and down in response to water currents which would have
provided the mechanical energy for making and breaking bonds," said
Hansma.

She summed up her hypothesis of the origin of life by saying, "I picture
all the molecules of early life evolving and rearranging among mica sheets
in a communal fashion for eons before budding off with cell membranes and
spreading out to populate the world."

IMAGE CAPTION:
[http://www.ia.ucsb.edu/pa/image.aspx...697&Position=1 (182KB)]
Biological molecules in spaces between mica sheets. Credit: Helen
Greenwood Hansma, UCSB


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