Good job bringing this to light. People won't realise how huge the problem is and municipalities are woefully ill equipped to...
Agreed; mining can never be sustainable, but then how do you get the metals to make all the things you need in the course of...
Very good piece.
THE discovery that a DNA molecule can
conduct electricity may help in repair of
damage caused in the molecule by exposure to the sun. This was tested by
attaching a chemical group at one end
of the DNA molecule, which is situated
some distance away from the chemically
damaged part. The experiment was conducted by Jacqueline Barton and her
team at the California Institute of
Technology, USA, who call the process
chemistry at a distance'.
The chemical mechanism is not
clear, but electrical conduction - the
flow of electrons down the DNA molecule - is thought to be involved. The
specific form of damagekhat was
repaired is known to be caused by ultraviolet (uv) rays, and Barton and her
team conjecture that this discovery
might offer hints as to how to treat at
least some of the harmful effects caused
by overexposure to the sun.
Barton and her team carried out a
number of experiments to show that
DNA is an unusual organic molecule in
that it can conduct electricity (proteins,
in contrast, are resistors). Though the
results of the experiments raised curiosity and interest, they did not convince
everyone. Four years ago, a direct measurement of the conductivity Of DNA
suggested that it is a better conductor
than expected for an electrical resistor.
However, this result could not be replicated by others.
The next experiment involved
attaching a molecule containing an
atom of ruthenium (which can donate
electrons) to one end of a 15 base-pair-
long DNA molecule. When irradiated by
photons, the ruthenium could be
induced to glow until it transferred an
electron and 'de-excited' itself. When
the experiment was repeated after
attaching a chemical containing rhodium (an acceptor of electrons), there was
no glow at all. The inference drawn by
the scientists was that electrons travelled
down so fast from ruthenium to rhodiurn that the glow was quenched before it
could be measured.
As this inference depended on a
negative result - on something not
being found - it did not have many
takers. More recently, Barton's team
performed another experiment. Here a
metal particle attached to one end of the
DNA molecule functioned as an electron
acceptor when subjected to excitation
by photons, while guanine bases situated some distance away acted as electron
donors. The efficiency of this process
was so low that many doubted a mediatory role played by DNA. On an average,
10 million photons were needed per
electron transfer reaction.
In the latest attempt to demonstrate
that DNA can perform chemistry at a distance, Barton's team used DNA molecules which contained a thymine dimer
(containing twice the number of atoms
as ordinary thymine), such as might be
caused by uv irradiation, and an electron-accepting rhodium particle at one
end of the molecule. When the sample
was exposed to visible light, the rhodium atoms got excited, and took an electron from the thymine dimer. This
repaired the damage done to the DNA.
Crucially, the efficiency of electron
transfer was the same at all distances. It
did not decrease in direct proportion to
the distance between the thymine dimer
and the metal complex, as would have
been the case if the intervening medium
- the DNA - had been a resistor. The
scientific community is sure to start
searching for evidence of electrical conduction by DNA in living organisms, and
also for the possible uses that the phenomenon can be put to.