Everything that living things do can be understood in terms of the jigglings and wigglings of atoms (R.P. Feynman)
Part of the Molecular Photonics group investigates the structure and dynamics ("jigglings and wigglings") of complex molecular systems by means of vibrational spectroscopy, in particular time-resolved and two-dimensional infrared spectroscopy. The investigated molecular systems include
- peptides and proteins
- soft matter
- liquid water and aqueous solutions
- catalytic transition-metal complexes
In all of these systems, the molecular motions take place on many time scales, ranging from less than a picosecond to microseconds and longer. Structural dynamics taking place on such vastly different time scales are difficult to investigate with conventional structure-resolving methods, but can be probed directly using time-resolved vibrational spectroscopy.
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An infrared probe of molecular structure and size
Inspired by ideas from NMR, we have developed InfraRed Diffusion-Ordered SpectroscopY (IR-DOSY), which simultaneously characterizes the size and the chemical structure of a molecule, or of a mixture of molecules.
Hydrogen bonds under stress
Combining two-dimensional infrared spectroscopy with stress-strain measurements sheds new light on the mysterious elastic properties of polyurethane.
Fastest rheometer in the world
Using a fluorescent molecular rotor in combination with ultrafast laser excitation, we measure liquid viscosities with nanosecond time resolution.
Separating a mix with 2DIR spectroscopy
Peak overlap of compounds in a mixture is often a problem in vibrational spectroscopy. Postdoc Federico Caporaletti found a solution to this problem by exploiting the ultrafast relaxation of the vibrational modes. This made it possible to study the unique behavior of water in supercooled sorbitol solutions.
How ice-nucleating proteins influence the structure of water
A combination of surface-specific and two-dimensional vibrational spectroscopy sheds new light on how some bacteria are able to induce the freezing of water.
The physics of entangled worms
Active matter (ensembles of particles that consume energy in order to move or exert force) often behaves very differently from normal matter. Using a sample that we bought in the pet shop on a Friday afternoon, we found that active "polymers" show unique phase-separation and shear-thinning behaviour.
New light on proteins at interfaces
Many proteins are located at interfaces for their biofunctionality, which makes them problematic to study with conventional methods. Infrared sum-frequency generation provides the solution.
Fastest molecular shuttle in the world
A shuttling rotaxane synthesized by the group of Fred Brouwer uses a clever harpooning mechanism to speed up the translational motion. Matthijs Panman measured the speed using time-resolved vibrational spectroscopy.
Solubility mystery solved
Why are some polyethers (such as POM, used to make Keck clips) completely insoluble in water, whereas others, such as PEG (present in nearly every cosmetic product), are perfectly miscible with water? A combination of spectroscopy experiments and computer simulations reveals the answer.
Van Gogh and 2D-IR spectroscopy
Using two-dimensional infrared spectroscopy, Joen Hermans has unravelled the structures of the zinc complexes involved in the degradation of zinc-white oil paint (used by Vincent van Gogh and other painters of his day). Joen's results shed new light on the humidity sensitivity of oil-paint ageing.
Non-cooperative water dynamics in salt solutions
The isotope-dependent response of salt solutions to oscillating electrical fields shows that water molecules surrounding ions behave in a less cooperative way than they do in bulk water. These findings lead to an update of the theory for the dielectric response of salt solutions developed by Nobel Laureate Onsager and his co-worker Hubbard, and enable a reliable determination of hydration numbers, which play a key role in chemistry and biophysics.
Two kinds of deeply supercooled water
Using a combination of calorimetry, molecular dynamics simulations and infrared spectroscopy, we investigated a liquid-liquid transition in supercooled aqueous solution.
Science 359, 1127 (2018) (freely accessible PDF)
The Making Of. The story of how this cooperation started, why supercooled water does not freeze, and what happened during the experiments is told in Sander Woutersen’s inaugural lecture:
Highlights about this article:
Molecular bicycle pedals
A molecular machine fueled by light and operating like the crankshaft and pedals of a bicycle. With infrared pulses you can see it working in real time.
A new twist to amyloid fibrils
The pathogenesis of Parkinson's disease is believed to involve the self-assembly of alpha-synuclein into amyloid fibrils. Surprisingly, when its last 32 amino acid are truncated alpha-synuclein forms much more strongly twisted fibrils.
Is "biological water" the same as tap water?
Everyone knows that plants and animals consist mostly of water. Does this water behave the same as normal tap water? To find out, we used time-resolved vibrational spectroscopy and dielectric-relaxation spectroscopy.
Measuring the tilt angle of a protein
The absolute orientation of interfacial proteins can be determined using phase-resolved sum frequency generation spectroscopy in combination with molecular dynamics simulations and spectral calculations.
New light on Parkinson's
The protein alpha-synuclein forms fibrillar aggregates that play a key role in the pathogenesis of Parkinson's disease. The morphology of the fibrils changes dramatically depending on the amount of salt in the surrounding buffer. 2D-IR spectroscopy reveals the underlying molecular mechanism.
Surprising finding under the hood of molecular motors
Time-resolved experiments on the molecular motor of Nobel laureate Ben Feringa show that its operation cycle involves an electronic 'dark state' that results in a small but important stutter in the rotational motion.
Solving water mysteries
Water containing antifreeze (glycerol) can be cooled down all the way to -100°C without freezing. At that temperature, the liquid undergoes a phase transition and changes into… another liquid?! 2DIR Spectroscopy reveals what is going on at the molecular level.
The redox behavior of a bio-inspired hydrogen-production catalyst
The Homogeneous Catalysis group of HIMS has achieved highly efficient hydrogen production using a synthetic catalyst that mimics the design of the iron-iron hydrogenase enzyme. The unique redox behavior of the catalyst was unraveled using time-resolved IR spectroscopy.
How guanidinium unfolds proteins
Guanidinium is a commonly used denaturant, but the mechanism by which it unfolds proteins is still largely unknown. We find that guanidinium disrupts the folded conformation by breaking salt bridges. 2D-IR spectroscopy shows that guanidinium binds to the carboxylate side groups involved in these salt bridges.
Switchable Amplification of Vibrational Circular Dichroism
Adding a ferrocene-based electrochemically switchable amplifier to a biomolecular system enables localized amplification of vibrational circular dichroism, making it possible to probe chirality in a site-specific manner.
Local orientational order in liquids
Ultrafast IR spectroscopy combined with molecular dynamics simulations shows that hydrogen-bonded liquids such as ethanol and N-methylacetamide are less 'random' that you might think.
Amplifying the optical effects of chirality
The vibrational circular dichroism of amino acids and oligopeptides can be enhanced by up to 2 orders of magnitude by coupling them to a paramagnetic metal ion.
Unraveling the structure of salt bridges in solution
Salt-bridge geometries can be determined by measuring the couplings between vibrations of the salt-bridged moieties using 2D-IR spectroscopy.