Hauer, who is a professor at the Technical University
of Munich (Germany), wanted to change this. He embarked on a pan-European collaboration with researchers at the University of Copenhagen, who specialize in
single molecule detection, and long-time colleagues at
the Italian university Politecnico di Milano, who had
already developed a compact spectrometer that perfectly
suited Hauer’s research needs.
The key to Hauer’s research lies in the Italian spectrometer’s ability to generate not one, but two laser
pulses, with a controlled delay in between. Hauer’s team
decided on a laser that has a broad frequency range—one
that mimics sunlight—to cover all visible wavelengths.
When using one laser, researchers can only excite at
a single wavelength, thus the data outputted is the fluorescence spectrum at that specific wavelength. The information missing is how the molecules behave at other
wavelengths. When using two lasers, the critical second
pulse modulates the emission spectrum in a specific
manner, which in turn provides information about the
absorption spectrum. This data is then evaluated using
a simple Fourier transformation.
“Two pulses allows us to encode the absorption
spectrum into the emission spectrum. Thus, in one measurement, we can record both the fluorescence and absorption spectrum of a single molecule,” Hauer explained
to Laboratory Equipment. "Previously, emission spectra
could be routinely acquired, but absorption measurements on individual molecules were extremely expensive.
We have now attained the ultimate limit of detectability."
In traditional spectroscopy, these kinds of measurements are averaged over thousands, even millions, of
molecules, sacrificing important molecule-specific information. For example, the bonds in an organic molecule may arrange differently when in a large structure.
While a researcher may classify a specific molecule as
mediocre in terms of light-harvesting, that may only
be the case since the data is averaged over a plethora
of additional, useless molecules. If the molecule can
be isolated as a singular entity, the researcher may discover it’s actually spectacular as light-harvesting.
“If you look at these molecules individually, you can
identify the structures that do the job very well,” Hauer
said. Then, it’s up to the organic chemists, material scientists and others to isolate the specific structure, mimic its
functions, and eventually employ it in an applied method.
End-stage collaboration with organic chemists and
material scientists is not the only teamwork propelling
this research forward, however. In fact, Hauer said,
the method he developed wouldn’t have been possible
without the device the Italian team had already created,
nor without the knowledge of single molecule detection
from the Copenhagen team.
“I couldn’t ask my co-workers to just build me a
single molecule setup by themselves, starting from an
empty room,” Hauer said. “That would be a waste of
taxpayers’ money. There is an instrument out there already in Copenhagen. You have to be willing to go out
and contact other experts in other fields, and then come
up with something creative together.
“You live and die by the quality of your collaborative
network,” he said.
Hauer and his group want to use the new method to
better understand the transfer of energy in biological
systems in which photosynthesis takes place; ultimately
accelerating the identification of efficient single molecules for future photovoltaic technologies.
For the next step, the Munich research team has cast
their sights on the natural light-harvesting complex LH2.
"Once we understand the natural light-harvesting
complexes, we can start thinking about artificial sys-
tems for deployment in photovoltaics," said Hauer. “I
want to understand natural systems, and then take that
knowledge and apply it to the design of artificial sys-
tems. I want to link artificial and natural light-harvest-
ing in this way.”
Ultimately, Hauer’s research goal is the development
of a novel, efficient organic solar cell.
Today’s researchers are interested in DNA for a multitude
of reasons—forensic scientists, for example, analyze DNA
for justice, while clinical scientists analyze it for disease
biomarkers. Alternatively, some early-stage physicists and
biologists analyze and manipulate “the blueprint of life”
to fuel tiny components for technical applications.
In a process known as DNA origami, scientists can
manipulate DNA in such a way that folding it creates
2- and 3-dimensional structures that can be used in a
variety of applications. One of the most notable applications is the development of nanomachines, or nanorobots
made partially or entirely of DNA that can switch between defined molecular conformations, and thus be used
as sensing, computing, actuating or therapeutic devices.
“In all these systems, the mechanical properties of
DNA molecules are of paramount importance,” said
Remy Pawlak, a postdoc in the physics laboratory at
the University of Basel (Switzerland).
However, DNA is finicky, and experimental conditions must be just right for scientists to glean the
information they desire. For example, the most common
DNA-manipulating techniques are performed using
an atomic force microscope (AFM), optical tweezers
or magnetic traps. In these experiments, DNA ends
are usually tagged with specific markers to attach the
molecules to the AFM tip apex, or trap its ends in the