|Aspirin’s Form I has a structure that is
more robust all-around, whereas Form II is strongest along one axis and weaker
on others, making the second version less stable.
Scientists in Berlin have just
cracked the case on a recently-raised question about one of the world’s most
popular medicines: aspirin. By taking into account previously-overlooked forces,
which only have significant effects at distances not much greater than the size
of an atom, the team was able to explain why aspirin’s molecules favor one crystal structure over another.
Speculation began in the early
2000s when calculations were published claiming that, although aspirin has a
unique and well-known structure, known as Form I, there is a second possible arrangement
occur just as often called
Form II. This result caused some dismay in the scientific community, since the
second form of the drug had never been observed.
Different versions of seemingly identical
molecules have caused medical disasters in the past, when a subtle property of
the morning sickness medication thalidomide caused nightmarish birth defects in
the late 1950s. For a drug employed as widely and indiscriminately as aspirin,
any unaccounted-for discrepancies might be a cause for serious concern. Researchers were later able to create the
predicted alternative crystal structure under special conditions, allaying medical
concerns when it was found that Form II turns back into Form I when subjected
to significant heat or pressure. However, the reason why the unusual,
surprisingly brittle new arrangement isn’t as common as Form I remained a
mystery until this year.
attributable to subatomic forces that lose
strength quickly with distance, which is why they had been ignored or
overlooked by previous investigators; other recent research has shown these
same forces to be responsible for the gecko’s miraculous clinging and climbing abilities. Taking into account the behavior
of charges within the molecule’s constituent atoms, rather than treating them as purely neutral
particles on the basis of equal proton and electron numbers, the team found
significant differences in the predicted favorability of Forms I and II.
of the physicist at a dinner party who calculates to everyone’s amazement that,
according to the laws of aerodynamics, bumblebees shouldn’t be able to fly.
Here, as in that story, the lesson appears to be that when discrepancies arise between
mathematical predictions and the observed universe, it’s usually the math that