Well maybe. I think there is plenty of opportunity in
basic organic chemistry to form coated water droplets that have sufficient
integrity to cook up something strange. Also
recall the work done mixing elementary chemicals in ice fractures for
decades. Clay itself is certainly useful
and suggestive since it is degraded volcanic ash which contains a lot of solid
crystalline acids to act as hammer and forge to produce more complex molecules.
My point is that a clay particle
is capable of strongly inducing chemical reactions. Thus it is a natural driver for the creation
of a protocell, but more like a catalyst than a structural template.
I think we are on the right track
to experimentally produce protocells that are able to mimic some of the key functions
of a cell.
Clay-Armored Bubbles May Have Formed First Protocells
by Staff Writers
Fatty-acid liposomes compartmentalize inside a clay vesicle. Credit:
Photo courtesy of Anand Bala Subramaniam, Harvard School of Engineering
A team of applied physicists at Harvard's
The research, published online this week in the journal Soft Matter,
shows that clay vesicles provide an ideal container for the
compartmentalization of complex organic molecules.
The authors say the discovery opens the possibility that primitive
cells might have formed inside inorganic clay microcompartments.
"A lot of work, dating back several decades, explores the role of
air bubbles in concentrating molecules and nanoparticles to allow interesting
chemistry to occur," says lead author Anand Bala Subramaniam, a doctoral
candidate at SEAS.
"We have now provided a complete physical mechanism for the
transition from a two-phase clay-air bubble system, which precludes any
aqueous-phase chemistry, to a single aqueous-phase clay vesicle system,"
Subramaniam says, "creating a semipermeable vesicle from materials that
are readily available in the environment."
"Clay-armored bubbles" form naturally when platelike
particles of montmorillonite collect on the outer surface of air bubbles under
water.
When the clay bubbles come into contact with simple organic liquids
like ethanol and methanol, which have a lower surface tension than water, the
liquid wets the overlapping plates. As the inner surface of the clay shell
becomes wet, the disturbed air bubble inside dissolves.
The resulting clay vesicle is a strong, spherical shell that creates a
physical boundary between the water inside and the water outside. The
translucent, cell-like vesicles are robust enough to protect their contents in
a dynamic, aquatic environment such as the ocean.
Microscopic pores in the vesicle walls create a semipermeable membrane
that allows chemical building blocks to enter the "cell," while
preventing larger structures from leaving.
Scientists have studied montmorillonite, an abundant clay, for hundreds
of years, and the mineral is known to serve as a chemical catalyst, encouraging
lipids to form membranes and single nucleotides to join into strands of RNA.
Because liposomes and RNA would have been essential precursors to
primordial life, Subramaniam and his coauthors suggest that the pores in the
clay vesicles could do double duty as both selective entry points and catalytic
sites.
"The conclusion here is that small fatty acid molecules go in and
self-assemble into larger structures, and then they can't come out," says
principal investigator Howard A. Stone, the Dixon Professor in Mechanical and
Aerospace Engineering at Princeton, and a former Harvard faculty member.
"If there is a benefit to being protected in a clay vesicle, this is a
natural way to favor and select for molecules that can self-organize."
Future research will explore the physical interactions between the
platelike clay particles, and between the liquids and the clay. The researchers
are also interested to see whether these clay vesicles can, indeed, be found in
the natural environment today.
"Whether clay vesicles could have played a significant role in the
origins of life is of course unknown," says Subramaniam, "but the
fact that they are so robust, along with the well-known catalytic properties of
clay, suggests that they may have had some part to play."
Clay-armored bubbles may have formed first protocells
February 7, 2011
Fatty-acid liposomes compartmentalize inside a clay vesicle. Credit:
Photo courtesy of Anand Bala Subramaniam, Harvard School of Engineering
(PhysOrg.com) -- A team of applied physicists at Harvard's School of Engineering
and Applied Sciences (SEAS), Princeton , and
Brandeis have demonstrated the formation of semipermeable vesicles from
inorganic clay.
The research, published online this week in the journal Soft Matter, shows
that clay vesicles provide an ideal container for the compartmentalization of complex organic
molecules.
The authors say the discovery opens the possibility that primitive
cells might have formed inside inorganic clay microcompartments.
"A lot of work, dating back several decades, explores the role of
air bubbles in concentrating molecules and nanoparticles to
allow interesting chemistry to occur," says lead author Anand Bala
Subramaniam, a doctoral candidate at SEAS.
"We have now provided a complete physical mechanism for the
transition from a two-phase clay–air bubble system, which precludes any
aqueous-phase chemistry, to a single aqueous-phase clay vesicle system,"
Subramaniam says, "creating a semipermeable vesicle from materials that
are readily available in the environment."
"Clay-armored bubbles" form naturally when platelike
particles of montmorillonite collect on the outer surface of air bubbles under
water.
When the clay bubbles come into contact with simple organic liquids
like ethanol and methanol, which have a lower surface tension than water, the
liquid wets the overlapping plates. As the inner surface of the clay shell
becomes wet, the disturbed air bubble inside dissolves.
The resulting clay vesicle is a strong, spherical shell that creates a
physical boundary between the water inside and the water outside. The
translucent, cell-like vesicles are robust enough to protect their contents in
a dynamic, aquatic environment such as the ocean.
The authors' schematic of clay vesicle formation, showing a cut-away
view of the clay shell and dissolving bubble at the top, and a view of the
water-air interface at the bottom. Credit: Image courtesy of Anand Bala
Subramaniam, Harvard School
of Engineering
Microscopic pores in the vesicle walls create a semipermeable membrane
that allows chemical building blocks to enter the "cell," while
preventing larger structures from leaving.
Scientists have studied montmorillonite, an abundant clay, for hundreds
of years, and the mineral is known to serve as a chemical catalyst, encouraging
lipids to form membranes and single nucleotides to join into strands of
RNA.
Because liposomes and RNA would have been essential precursors to
primordial life, Subramaniam and his coauthors suggest that the pores in the
clay vesicles could do double duty as both selective entry points and catalytic
sites.
"The conclusion here is that small fatty acid molecules go in and
self-assemble into larger structures, and then they can't come out," says
principal investigator Howard A. Stone, the Dixon Professor in Mechanical and
Aerospace Engineering at Princeton, and a former Harvard faculty member.
"If there is a benefit to being protected in a clay vesicle, this is a
natural way to favor and select for molecules that can self-organize."
####
This SEM image shows the exterior surface of a clay vesicle. Photo
courtesy of Anand Bala Subramaniam.
Future research will explore the physical interactions between the platelike
clay particles, and between the liquids and the clay. The researchers are also
interested to see whether these clay vesicles can, indeed, be found in the
natural environment today.
"Whether clay vesicles could have played a significant role in the
origins of life is of course unknown," says Subramaniam, "but the
fact that they are so robust, along with the well-known catalytic properties
of clay, suggests that
they may have had some part to play."
No comments:
Post a Comment