© Stock.Adobe.com/au/Kenishirotie
quality control
Chiral spectroscopy: quality control for twisted molecules It’s not easy to be sure that drugs and supplements with twisted (chiral) structures are turning in the correct direction. Now researchers in the US and Brazil have shown that twirling infrared light can probe both the structures of molecular crystals and their twists, confirming that they are safe and effective.
W
“The methods most commonly used at
signature. The researchers thus hope their method
pharmaceutical companies are very sensitive to
could enable rapid diagnostics for pets and perhaps
impurities, but measuring chirality is expensive,”
later humans, diagnosing harmful accumulations
said Wonjin Choi, a research fellow at the
of twisted molecules in the body including bladder
University of Michigan (U-M) and first author
stones, insulin fibrils and amyloid aggregations such
on the study. The method developed by Choi and
as the plaques that appear in Alzheimer’s disease.
colleagues can quickly recognise wrong twists and
In addition, the researchers studied insulin as
wrong chemical structures in packaged drugs using
it grew into nanofibres that make it inactive. If the
terahertz radiation, a portion of the infrared part of
terahertz light technology can be adapted for home
the spectrum. It has been described in the journal
health care, it could verify the quality of insulin.
Nature Photonics.
The team also explored how light can influence
“Biomolecules support twisting, long-range
structures, rather than just measure them.
vibrations also known as chiral phonons,” explained
Calculations carried out by co-corresponding
U-M Professor Nicholas Kotov, co-corresponding
author Professor André Farias de Moura, from the
author on the study. “These vibrations are very
Federal University of São Carlos, show that multiple
sensitive to the structure of molecules and their
biomolecules vigorously twist and vibrate when
nanoscale assemblies, creating the fingerprint of
terahertz light generates chiral phonons.
a particular chiral structure.”
“We foresee new roads ahead — for instance,
The team was able to measure these phonons
using terahertz waves with tailored polarisation to
alking along the supplement
in the spectra of twisted terahertz light that passed
manipulate large molecular assemblies,” Prof de
aisle, you might notice that some have an L or D
through tested materials. One of these, L-carnosine,
Moura said. “It might replace microwaves in many
in front of the names. This denotes the direction
is currently used as a nutritional supplement.
synthesis applications in which the handedness of
in which the molecule twists, ie, clockwise (D) or
“If the twist of the molecule is wrong, if the
anticlockwise (L) — the human body typically only
twist in the way the molecules pack together is
Based on Prof de Moura’s calculations,
uses one version. Molecules with the wrong twist
not right, or if different materials were mixed in,
Prof Kotov and Choi believe that the twisting
can be nuisance fillers or cause side effects that can
all of that could be inferred from the spectra,”
vibrations of chiral phonons caused by terahertz
be unpleasant or dangerous. But quality control for
Prof Kotov said.
light may make disease-causing nanofibres more
the molecules matters.”
twisted molecules is tough, and monitoring the
Study co-author Professor John Kruger, from
vulnerable to medical interventions. Future work
chiral structures of drugs and supplements kept
Michigan State University, provided bladder stones
will explore whether that interaction can be used
in storage isn’t usually done.
from dogs, and the team discovered their chiral
to break them up.
www.LabOnline.com.au | www.LifeScientist.com.au
LAB+LIFE SCIENTIST - Apr/May 2022 | 17
