Chips and DNA
From industrial microchips to gene analysis,
research benefits from the powerful FEL
Being able to drill clean holes in very brittle materials is as much
a boon to dentists and doctors as it is to those in the electronics business.
Richard Haglund, professor of physics and astronomy, thinks that
putting together materials for communications and electronics using the
free-electron laser is just as exciting as laser surgery.
"The studies of hard tissue (bones and teeth) ablation that we are
working on are directly benefitted and correlate strongly with work being
done on other materials. The body is made up of the same materials found
in other good strong materials. The enamel structures in teeth, for example,
and bones are put together out of the same kinds of phosphate and carbonate
groups in inorganic materials," says Haglund.
Haglund and Hee Park, research associate in laser physics, use the FEL
to create microstructures on surfaces such as tiny structures in industrial
chip-making materials and precise incisions in surgery.
Using the FEL on dental tissues has resulted in chemical changes producing
preventative treatments against decay, as well as other dental applications
like painless drilling, permanently bonded tooth whitening and permanent
welding between tooth and filling or crown.
"Often the polymer adhesives used to hold in a filling fall apart
and you have to go to the dentist and get a tooth refilled. The FEL molds
the two parts into one piece giving a permanent bond so you never lose a
filling again," Park says.
Another area of research involves analyzing genes and speeding up the lengthy
process of gene sequencing.
"Techniques for analyzing human genes is extremely tedious using traditional
analytic chemical techniques because it takes a long time. A blood test
for DNA analysis takes more than a week, maybe months, to get the results.
But if you put the laser on the sample, the sample will be vaporized and
ejected. Then we measure the properties of the ejected material and do an
analysis of those materials," says Park.
This process of vaporizing materials to be analyzed is made possible through
FEL-MALDI or Matrix-Assisted Laser-Desorption and Ionization. Haglund was
the first scientist to apply the FEL to MALDI.
Through MALDI, DNA fragments to be sequenced are suspended in a matrix that
selectively absorbs infrared light from the FEL. When the matrix is vaporized
by the laser, intact fragments of the DNA molecule are transported out of
the matrix in a jet of vaporized matrix material to be "weighed"
for sequencing in an instrument called a mass spectrometer. A matrix donates
laser energy to the material to be analyzed so it can fly away from the
surface without losing its identity. There is complete freedom in choosing
a matrix material because of the ability to tune the FEL's wavelength.
Sequencing of DNA can be sped up by a factor of 100 or more using the MALDI
technique. The new spectrometry technique could also lead the way to a new
generation of instruments for analyzing not only DNA, but also other biological
molecules such as complex carbohydrates. Large molecules such as proteins
can be analyzed using FEL infrared mass spectrometry by measuring the mass
of emitted molecules.
"The laser desorption mass spectrometry also allows us to look at
the buildup of molecules during the healing process; for example, at the
way fibroblasts get turned from single molecules to polymers so that you
get the long stringy fibers built up to repair tissue," Haglund says.
- Ellen Bourne
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This document created November 19, 1996