Since
the development of the modern
optical microscope, we have been limited to
viewing microscopic objects at a resolution of
roughly 250 nm. Even with a perfect microscope
– that is, one not limited by lens imperfections or
alignment issues – for a while it was thought that
we cannot bypass this diffraction limit, which is
half the wavelength of light. The diffraction limit
is enough to examine most biological cells but
smaller biological components such as viruses
or proteins lie outside of this range. Attempts to
circumvent the diffraction limit have involved the
use of shorter wavelengths such as ultraviolet or
X-ray but these rays can damage cellular matter
and thus are not entirely suitable for biological use.
The development of super-resolved fluorescence
microscopy, however, has taken microscopy to the
next level.
In 2014, Prof. William E. Moerner was recognised
for his work in the development of super-resolved
fluorescence microscopy with a joint Nobel Prize
in Chemistry with Prof. Eric Betzig and Prof. Stefan
W. Hell. Currently serving as the Harry S. Mosher
Professor in Chemistry and Professor of Applied
Physics by Courtesy at Stanford University, Prof.
Moerner holds, impressively, three bachelor’s
degrees and a Ph.D. in physics.
The development of super-resolution involving
single molecules began in the 80’s. Working
together with his postdoc, Lothar Kador, at IBM
Research in San Jose, Prof. Moerner was the first
Further reading
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popular-chemistryprize2014.pdf
person to optically detect a single molecule,
through the use of laser frequency modulation
spectroscopy. In 1997, they obser ved green
fluorescent proteins (GFP), which exhibit bright
green fluorescence if exposed to the lower
wavelengths of the v i s ible l ight range and
subsequently discovered that GFPs can blink and
be optically switched.
His award-winning work has revolutionised the
visualisation of objects on the nanoscopic scale.
Optical study of single molecules and molecular
mechanisms of living cells have become possible
due to the development of super- resol ved
fluorescence microscopy, expanding microscopy to
nanoscopy. In our interview, he explained that the
structure of interest is first labelled with fluorescent
dyes. Then these single-molecule emitters are
viewed under conditions where only a few are
emitting at a single time via photoactivation,
for example. The positions of the emitters are
pinpointed, which continue over some time, where
the single points of light allow sampling of many
positions of the structure, until the full structure is
constructed. The end product is a computational
image formed with tiny points of light.
In the past, scientists were only able to study
many molecules simultaneously and take an
average of al l those results. Super- resolved
fluorescence technology has enabled the study
and image single molecules, allowing for much
more accurate and detailed information. “If we
can watch them one by one, then we can learn
much, much more”. Prof. Moerner’s current work
By Cherry Chow
周卓瑩
Breaking Boundaries:
