A Syracuse Univ. chemist has developed a way to use very low
frequency light waves to study the weak forces (London dispersion forces) that hold molecules
together in a crystal. This fundamental research could be applied to solve
critical problems in drug research, manufacturing, and quality control.
The research by Timothy Korter, associate professor of
chemistry in SU’s College
of Arts and Sciences, was
the cover article of Physical Chemistry
Chemical Physics.
“When developing a drug, it is important that we uncover all
of the possible ways the molecules can pack together to form a crystal,” Korter
says. “Changes in the crystal structure can change the way the drug is absorbed
and accessed by the body.”
One industry example is that of a drug distributed in the
form of a gel capsule that crystallized into a solid when left on the shelf for
an extended period of time, Korter explains. The medication inside the capsule
changed to a form that could not dissolve in the human body, rendering it
useless. The drug was removed from shelves. This example shows that it is not
always possible for drug companies to identify all the variations of a drug’s
crystal structure through traditional experimentation, which is time consuming
and expensive.
“The question is,” Korter says, “can we leverage a better
understanding of London
and other weak intermolecular forces to predict these changes in crystal
structure?”
Korter’s lab is one of only a handful of university-based
research labs exploring the potential of THz radiation for chemical and
pharmaceutical applications. THz light waves exist in the region between
infrared radiation and microwaves and offer the advantages of being non-harmful
to people and able to safely pass through many kinds of materials. THz can also
be used to identify the chemical signatures of a wide range of substances.
Korter has used THz to identify the chemical of signatures of molecules ranging
from improvised explosives and drug components to the building blocks of DNA.
Korter’s new research combines THz experiments with new
computational models that accurately account for the effects of the London dispersion forces
to predict crystal structures of various substances. London forces are one of several types of
intermolecular forces that cause molecules to stick together and form solids.
Environmental changes (temperature, humidity, light) impact the forces in ways
that can cause the crystal structure to change. Korter’s research team compares
the computer models with the THz experiments and uses the results to refine and
improve the theoretical models.
“We have demonstrated how to use THz to directly visualize
these chemical interactions,” Korter says. “The ultimate goal is to use these
THz signatures to develop theoretical models that take into account the role of
these weak forces to predict the crystal structures of pharmaceuticals before
they are identified through experimentation.”
SOURCE
