Posted on 07/14/2004 10:54:58 PM PDT by neverdem
n an advance that could lead to three-dimensional pictures of proteins and other molecules, scientists have developed a magnetic resonance imaging technique that can detect a single electron.
"There's lots of things this will be useful for," said Dr. Daniel Rugar, manager of nanoscale studies at I.B.M.'s Almaden Research Center in San Jose, Calif., and leader of the research team, which is reporting the findings today in the journal Nature. "There are thousands of proteins in the body whose structures are not known."
It is largely proteins' shapes that enable them to carry out the essential functions of the body, and researchers hope that knowing those shapes will help them devise drug therapies. Determining the shape is currently an indirect, arduous process: purifying the protein, assembling it into crystals and deducing the shape from the pattern of X-rays bounced off a crystal.
In the future, a scientist may be able to take a protein, insert it into a molecular magnetic resonance imaging, or M.R.I., machine and "simply take a three-dimensional image of a single molecule," Dr. Rugar said, just as today's medical M.R.I. machines provide clear pictures of flesh and blood for doctors to examine.
The images could also directly show how drug molecules interact with proteins, identify viruses or biological weapons and identify the locations of specific atoms in molecular-scale electronic devices. Current atomic-scale instruments like atomic force microscopes can only map the surface, not look at the three-dimensional structure of individual molecules.
"That would change how we do science," said Dr. John A. Marohn, a professor of chemistry at Cornell University who was not involved in the research. "This is a holy grail for science, for chemistry, physics and biology."
The I.B.M. experiment, culminating years of research, is "a major, major milestone" toward the goal of three-dimensional molecular images, Dr. Marohn said.
The technology could also find use in the future in so-called quantum computers, which will be able to calculate many possibilities at once. A quantum computer might use the magnetic orientation of electrons to store data, and a variation of the I.B.M. technique could be used to write or read information in the computer.
Magnetic resonance imaging takes advantage of the fact that subatomic particles like electrons and the nuclei of atoms behave like tiny bar magnets and, when placed in a magnetic field, spin around like tops. In medical M.R.I. scans, the spinning of trillions of hydrogen nuclei in water molecules generates radio waves that are collected to create images.
A single electron, however, generates too weak a radio signal to be detected. The I.B.M. team instead observed the magnetic signal of the electron by its effects on a microscopic magnet.
The magnet, attached to the end of a cantilever, a microscopic diving board one-thousandth the thickness of a hair, vibrated back and forth 5,000 times a second.
Just as any two bar magnets would, the microscopic magnet on the cantilever and the electron attracted or repelled each other, depending on the orientation of their magnetic fields.
An additional oscillating magnetic field caused the electron to flip each time the microscopic magnet swung past. The magnetic forces slightly sped up or slowed the frequency of the cantilever vibrations, by about 0.0001 percent, which the researchers were able to measure.
That corresponds to a force of less than a millionth of a trillionth of a pound and an improvement in sensitivity over current M.R.I. techniques.
"This particular experiment is a breakthrough because it marks our first entry into the quantum realm," said Dr. John A. Sidles, a professor of orthopedics at the University of Washington who first proposed this approach for M.R.I. in 1991. "I think it's really, really neat."
While the M.R.I. detection of electrons could find some applications, the hope of taking pictures of molecules requires detecting atomic nuclei, whose magnetic strength is only one-650th that of electrons. The experiment also took more than half a day to detect the one electron.
Dr. Rugar said he was confident that he could improve sensitivity and speed by shrinking the size of the cantilever and magnet and running the experiment at colder temperatures, less than a degree above absolute zero. A practical molecular M.R.I. microscope could still be a decade away.
PING
It is working Doktor.
You should change your name to Speedy Gonzalez. Thank you!
http://www.yuckles.com/tweety/speedy.html
You're welcome
hehehe :)
The same Robin Williams?
RW is a bit hyper.
I think the microtome is a little dull.
Microcantilevers are going to provide a lot of cool and useful stuff.
Thanks for the clarification about the news article that I linked at Nature.com, and the abstract from the article in Nature. I haven't looked at Nature or Science in ages. I'll be quite happy to see if Science has a similar Science.com ASAP.
It appears that there are no freebies at Science, or did I miss something?
BTTT
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