Electrons 'tunnel' through water molecules between nestled
proteins
November 28, 2005
Laptop Battery DURHAM, N.C. - Duke University theoretical chemists who spend
much of their time calculating how the exotic rules of quantum
mechanics govern electrons motion between and through biological
molecules have garnered surprising results when they add water to
their models.
radical damage takes place on an atomic level. Molecules are made of atoms, and a single atom is made up of protons, neutrons, and electrons. Electrons are always found in pairs. However, when oxygen molecules are involved in a chemical reaction, they can lose one of their electrons. This oxygen molecule that now has only one electron is called a free radical. With only one electron the oxygen molecule must quickly find another electron, and it does this by taking the electron from another molecule. When that molecule in turn loses one of its electrons, it too must seek out another, in a continuing reaction. Molecules attempting to repair themselves in this way trigger a cascading event called " radical damage." radical damage takes place in a fraction of a second. Antioxidants are substances that prevent oxidative damage from being triggered. See antioxidant.
Thinkpad They have discovered that a scant handful of water molecules
positioned in the nearly infinitesimal gap between two "docking"
proteins creates unexpectedly favorable conditions for electrons to
"tunnel" from one protein to another. The researchers, chemistry
professor David Beratan and postdoctoral researchers Jianping Lin
and Ilya Balabin, revealed their findings in a paper to be
published in the Nov. 25, 2005, issue of the journal Science.
generating process by acting as a shuttle to transport both electrons and protons from one bioenergy enzyme to another. Each CoQ molecule carries electrons and protons from donor enzymes to acceptor enzymes. They then return to pick up more electrons and protons. over again, thousands of times a second! Every electron and proton from which energy is to be extracted must first be transported to that appropriate enzyme by a molecule of Coenzyme Q10
Microsoft Their work, supported by the National Institutes of Health,
delves into puzzling guidelines of physics that Beratan said nature
has to follow in order to harness energy and avoid disease.
Computer memory is the quickest, cheapest, and easiest way to improve the performance of your system. Find RAM memory upgrades for desktops, laptops, servers, and printers all backed by a lifetime warranty and guaranteed compatible with your computer. Shipping is an everyday low price of $1.99! Computer Memory Outlet sells memory compatible with all leading computer manufacturers like Dell, Apple, Compaq, HP, Sony, IBM, Lenovo, and many more.”
Laptop Computers "Electrons have dual characteristics, sometimes acting like
billiard balls and sometimes like waves on a pond," Beratan said in
an interview. "As a consequence, electrons do very peculiar things.
One thing they can do is tunnel through barriers forbidden to them
under the 'classical' rules of physics.
Three covalent bonds. Each of the three lines represents the shared pair of electrons in a covalent bond. Some textbooks omit the nonbonding electrons for simplicity. Because the hydrogen atom has its single 1 s orbital completed with only 2 electrons, the hydrogen chloride molecule is drawn as shown in Figure 7 . Figure 7 The hydrogen chloride molecule.
Laptop Computer "Biology has to move electrons through proteins in order to trap
energy from the sun, capture energy from our food, and control
damage to living systems," he added. "So biology has had to come to
terms with this duality. Although electrons have the ability to
tunnel, it's very costly for them. But one thing that proteins seem
to do is to guide such electrons from place to place."
Some forms of cancer are thought to be caused by what are called free radicals, naturally occurring renegade molecules that damage your body's healthy molecules (such as DNA, in the case of cancer) by stealing electrons to balance themselves. Vitamin C and other substances known as antioxidants neutralize free radicals by offering their own electrons, minimizing oxidative damage to DNA and other molecules, explains Balz Frei, Ph.D., associate professor of medicine and biochemistry at Boston University School of Medicine. - - - -are also neutralized by vitamin C.
Desktop Computer Scientists have already deduced that electron movements are
enhanced when proteins fold into complex three-dimensional shapes
in their active forms. "It is much easier for electrons to tunnel
quantum mechanically through a folded protein than it is for them
to penetrate empty space," he said.
Notebooks Beratan said he and other Duke chemists have spent years
studying proteins' roles in electron transport. But only recently
has his group addressed how water between protein molecules affects
electron movement.
Lenovo For instance, whenever two proteins that transfer electrons
interact strongly - or "dock" - they must exchange electrons in a
watery medium. What scientists didn't understand was the role of
water at this interface, he said.
Hard Drive According to Beratan, electrons cannot simply hop over the very
small half billionths of a meter gaps that separate such docking
proteins. Quantum mechanics requires that those electrons instead
follow pathways or conduits that are heavily influenced by the
positions of nearby atoms and gaps between atoms.
Travelstar "What our study was about was probing how that tunneling process
changes if we begin pulling two proteins apart and the gap between
them fills with water," he said.
Gateway "What we show is that at the shortest separations electrons take
advantage of the proteins in tunneling between those two molecules.
But there is an intermediate distance where the proteins are beyond
contact and the water molecules start moving into this
interface.
Laptop Parts "In this intermediate distance before the proteins are too far
apart, the water plays a very special role in mediating the
electron tunneling more strongly than might have been
expected."
Software An illustration in their Science paper, derived from massive
computer studies by the authors, shows how a mere handful of those
water molecules can form an organized cluster under the influence
of the protein molecules on either side of the gap. This cluster
aids the electron transfer process, he said.
Hard Drives Electrons can then tunnel between "donor" atoms at the tip of
one protein to "acceptor" atoms on the other protein. Along the
way, the electrons follow multiple pathways through these water
molecules that facilitate the transport more strongly than
expected.
Electronics "Before our study, expectations for electron tunneling were that
interactions between the electron donor and acceptor through water
would drop exponentially as a function of the distance," Beratan
said.
Canon "What we found was that water is a better mediator for electron
transfer at intermediate distances than anybody had expected.
Another finding was that the water-mediated tunneling drops only
very slightly as a function of distance within this intermediate
length."
Desktop Pc The Duke team's computations show tunneling initially dropping
off very rapidly when the proteins first start separating - just
like scientists originally expected. But at intermediate distances
of a few tenths of a billionths of a meter "the rates of tunneling
don't change very much," he said. "Then, when the proteins are
separated somewhat further, the rates again drop exponentially
again as a function of their separation distance," he added.
Desktop Computers Experiments in the Netherlands as well as at the University of
California, Berkeley also suggest a special role for water in
promoting electron transfers between proteins, he said.
Think Pad "You could think about the structure of the proteins as well as
the water as guiding or shepherding the electrons," Beratan said.
"So evolution has had to come to terms with physics in the way
protein and water direct electrons through complex structures."
Repair The study was the final Ph.D. project for Lin, Beratan's former
graduate student, who is first author of the Science paper.
Co-author Balabin helped the group calculate how the naturally
occurring motion of atoms in the protein might further influence
the electron transfer.
Data Recovery "We see pictures of proteins in fixed positions, but in reality
we should think of their atoms as wiggling all over the place,"
Beratan said.
Cisco Duke University
[ Comment, Edit or Article Submission ]
