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Scientists discover first new chlorophyll in 60 years
http://www.physorg.com/news201502581.html
August 20, 2010
(PhysOrg.com) -- University of Sydney scientists have stumbled upon
the first new chlorophyll to be discovered in over 60 years and have
published their findings in the international journal Science.
Found by accident in stromatolites from Western Australia's Shark Bay,
the new pigment named chlorophyll f can utilise lower light energy
than any other known chlorophyll.
The historic study published online in Science, challenges our
understanding of the physical limits of photosynthesis - revealing
that small-scale molecular changes to the structure of chlorophyll
allows photosynthetic organisms to survive in almost any environment
on Earth.
The new chlorophyll was discovered deep within stromatolites -
rock-like structures built by photosynthetic bacteria, called
cyanobacteria - by lead author Dr Min Chen from the University of
Sydney.
A team of interdisciplinary scientists, including Dr Martin Schliep
and Dr Zhengli Cai (University of Sydney); Associate Professor Robert
Willows (Macquarie University); Professor Brett Neilan (University of
New South Wales) and Professor Hugo Scheer (University of Munich),
characterised the absorption properties and chemical structure of
chlorophyll f, making it the fifth known type of chlorophyll molecule
on Earth.
Chlorophyll is the essential molecule in oxygenic photosynthesis - the
process that enables plants, algae and some bacteria to convert carbon
dioxide into sugar and oxygen by using free energy from sunlight.
Until recently, oxygenic photosynthesis was thought only to occur in
light that is visible to human eyes, between 400nm to 700nm, as
chlorophyll was strictly limited to absorbing light in this range.
This was overturned in 1996 when scientists found a cyanobacterium
that could photosynthesise using light just outside the visible
spectrum - at 710nm, in the infrared region - using a modified
chlorophyll molecule, named chlorophyll d. Since this discovery,
scientists around the world have been puzzled by how chlorophyll d is
able to get enough energy from infrared light for photosynthesis.
Now the rules of photosynthesis need to be rewritten again, with the
discovery of a new chlorophyll that can absorb light of even lower
photon energy - 720nm - making it the most red-shifted chlorophyll to
date.
In ecological terms, chlorophyll f allows cyanobacteria living deep
within stromatolites to photosynthesise using low-energy infrared
light, the only light able to penetrate into the structure, which
challenges further our understanding of the physical limits of
photosynthesis.
Dr Chen, from the School of Biological Sciences, explains: "Finding
the new chlorophyll was totally unexpected - it was one of those
serendipitous moments of scientific discovery.
"I was actually looking for chlorophyll d, which we knew could be
found in cyanobacteria living in low light conditions. I thought that
stromatolites would be a good place to look, since the bacteria in the
middle of the structures don't get as much light as those on the
edge."
Scientists discover first new chlorophyll in 60 years
Cross section of a Shark Bay stromatolite. The layers are different
microbial communities, each with very different physiologies.
After obtaining a sample of stromatolite from Hamelin Pool, Dr Chen
looked for chlorophyll d by culturing the cyanobacterial sample in
infrared light of 720nm. This ensured only the survival of
cyanobacteria that had chlorophylls able to absorb and use infrared
light.
High performance liquid chromatography of the cultured sample
performed six months later revealed not only trace amounts of
chlorophyll d, but also a new chlorophyll not seen before.
Testing the optical absorption spectrum of the new chlorophyll
revealed that it could absorb much longer wavelengths of light than
any other known chlorophyll - 10nm longer than chlorophyll d and more
than 40nm longer than chlorophyll a.
Sequential mass spectral analysis revealed the molecular weight of the
new pigment to be 906 mass units. Then nuclear magnetic resonance
(NMR) spectroscopy was performed to determine the chemical structure
of the chlorophyll. Results indicated that chlorophylls a, b, d and f
have very similar chemical structures, differing only in the position
of a substitution. Yet these tiny differences in structure give the
chlorophylls very different spectral properties, and hence can
function in very different light environments.
"Discovering this new chlorophyll has completely overturned the
traditional notion that photosynthesis needs high energy light," Dr
Chen said.
"It is amazing that this new molecule, with a simple change to its
chemical structure, can absorb extremely low energy light. This means
that photosynthetic organisms can utilise a much larger portion of the
solar spectrum than we previously thought and that the efficiency of
photosynthesis is much greater than we ever imagined.
"Chlorophyll f, and its ability to absorb infrared light, can have
numerous applications to industries like plant biotechnology and
bioenergy.
"For us, the next challenge is to work out the function of this new
chlorophyll in photosynthesis.
"Is its job to capture additional red light and pass it on to another
chlorophyll, like chlorophyll a, in the reaction centre for
photosynthesis?
"Or is it the only chlorophyll responsible for photosynthesis in the
cyanobacterium? And if it is, then we will be speechless wondering how
this molecule can get enough energy from infrared light to make oxygen
from water.
"Whatever happens next, the fact that we have discovered a
cyanobacterium that exploits a tiny modification in its chlorophyll
molecule to photosynthesise in light that we cannot see, opens our
mind to the seemingly limitless ways that organisms adapt to survive
in their environment."
More information: http://www.science … ence.1191127
Provided by University of Sydney
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"Ethics" is simply a last-gasp attempt by deist conservatives and
orthodox dogmatics to keep humanity in ignorance and obscurantism,
through the well tried fermentation of fear, the fear of science and
new technologies.
There is nothing glorious about what our ancestors call history,
it is simply a succession of mistakes, intolerances and violations.
On the contrary, let us embrace Science and the new technologies
unfettered, for it is these which will liberate mankind from the
myth of god, and free us from our age old fears, from disease,
death and the sweat of labour.
Rael
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