Quantum biology has the potential to become the next big research coup. Professor Martin Plenio, 46, director of the Institute of Theoretical Physics at Ulm University and one of the world’s leading quantum technologists, is right at the forefront. He has been Alexander von Humboldt Professor since 2009, and holds a part-time professorship at Imperial College London, where he was formerly chair of quantum physics.
Prof. Dr. Martin Plenio and some of his renowned colleagues from the University of Ulm’s (quantum and bio-) physics, chemistry and medicine departments aim to “measure biological phenomena on an unprecedented scale with unmatched precision”. This new branch of science, into which the EU (an ERC Synergy Grant), the German and Baden-Württemberg governments as well as the University of Ulm have injected around 40 million euros for the construction of a new research building, is risky, innovative and interdisciplinary.
If the researchers achieve what they are setting out to do, their work will result in economically significant technologies for use in medical diagnostics, attractive savings for the pharmaceutical industry and the optimization of organic solar cells. Construction of Ulm University’s Centre of Quantum Biological Science (ZQB), which will be the first of its kind in the world, is expected to finish in 2017 and will provide workspace for over 100 people. The other members of the ZQB founding board of directors besides Martin Plenio are Prof. Dr. Fedor Jelezko, experimental physicist and director of the Institute of Quantum Optics, Prof. Dr. Tanja Weil, director of the Institute of Organic Chemistry III, and Prof. Dr. Frank Kirchhoff, director of the Institute of Molecular Virology.
Quantum biology is currently being hailed as a new branch of research. However, the idea that led to it is much older. As far back as 90 years ago, the discoverers of quantum mechanical processes were interested in the effects of the newly discovered natural laws on our understanding of biological phenomena. The first of these was the German physicist Prof. Dr. Pascual Jordan, "the unsung hero of quantum physics" (FAZ, 12.11.2003). However, Jordan lacked the methods to test his ideas experimentally. Plenio points out it has only been possible to observe and quantitatively study quantum mechanical effects in natural systems for the last ten years or so.
In 2007, a group of scientists from the University of California, Berkeley, did a groundbreaking experiment with the bacteriochlorophyll complex of the photosynthesis system of green sulphur bacteria using femtosecond two-dimensional laser spectroscopy (doi:10.1038/nature05678) to find out how energy is transferred from the light-harvesting complex to the reaction centre. They identified quantum mechanical effects as the key to the effective, near-perfect transfer of energy. The publication caused a worldwide sensation. Similar experiments in algae and higher plants have since provided further evidence for the researchers’ observations.
In photosynthesis, electromagnetic radiation (visible light) is absorbed by the so-called light-harvesting complex (complex consisting of chlorophyll and proteins which is also known as antenna complex), and the energy of the light is captured as electron holes, so-called excitons. The excitons transfer the energy from the light-harvesting complex to the reaction centre in an extremely effective and ultra-rapid process that cannot be explained with the laws of classical physics. The only mechanism that can explain this is quantum mechanical. Plenio explains: “The energy is not transferred evenly, but in wavelike oscillations through quantum coherence.” Plenio and his colleagues have found out that the pigments (bacteriochlorophylls) of the light-harvesting complex are arranged in a specific way, resulting in the effective transport of the excitations from the light-harvesting complex to the reaction centre, where exciton energy is bound in chemical form. It appears that nature has optimized the pigment-protein complex such that the energy transport network components are able to interact efficiently and to exploit the vibrations of the complex.This energy transport network is found in many light-harvesting photon antennas in the pigment-protein complex. The Fenna-Matthews-Olson antenna complex in green sulphur bacteria, which transfers energy from the antennae to the reaction centre (Huelga, 2013), is one such complex.
But how can fragile quantum mechanical phenomena that are otherwise only observed in ultra-insulated, extremely cold and vacuum equipment survive in living "dirty" nature? Plenio sees no contradiction because quantum mechanical phenomena such as those which occur in photosynthesis take place in billionths of a second, i.e. they are so quick that they are not completely destroyed by the disturbing influences of biological systems.As things stand at the moment, there is evidence that quantum mechanical processes are essential for the understanding of the energy transport in photosynthesis, but evidence is still lacking for two biological phenomena that are also believed to require quantum mechanical processes, namely magneto-reception in birds and the olfactory sense.
Researchers at the ZQB in Ulm will use a custom-made microscope based on nanodiamonds to study biological phenomena. The researchers will be taking advantage of the nitrogen-vacancy defect centres in the diamond crystal and using them as highly sensitive magnetic field nanosensors for determining the position of atoms and the structure of a protein or a biomolecule. “This is our goal. In theory it is possible,” says Plenio.
Existing imaging methods are unable to provide such detailed insights into biological processes. Magnetic resonance spectroscopy needs 1012 molecules for creating a signal; X-ray diffraction analysis requires fewer molecules. However, the latter still requires several million molecules to create a signal. In addition, the molecules need to be crystallized, placed in a vacuum and exposed to X-rays, something that makes the technologies totally unsuitable for investigating proteins in their natural environment. Electron microscopes use accelerated electron beams in vacuum environments, which quickly damages the molecules under investigation. In addition, STED microscopy, for which Stefan Hell was awarded the Nobel Prize in Chemistry, only works with high light intensities and Plenio doubts that it is suitable for studying the structure of proteins.
Nanodiamonds are between 2 and 5 nanometres in diameter and have a very high absorption rate, which allows them to adhere to proteins with specifically treated surfaces. They are already used for a broad range of applications, but it will be a long time before they are suitable for in vivo measurements. Although the initial steps will have to be carried out in a physics laboratory, Plenio can see nothing to prevent nanodiamonds being suitable for such purposes. The lattice-like structures of nanodiamonds are technically sophisticated structures and are not easy to maintain. However, relatively effective approaches that enable the customized design of such nanomicroscopes are available and will now be optimized at the ZQB to make them suitable for application in the life sciences as well as for studying fundamental research questions and identifying areas of application. The interdisciplinary ZQB pools Ulm University’s excellence in the life sciences and the natural sciences in general.
Researchers never know whether their work will be successful or not. Nevertheless, the Ulm researchers are quite confident. What if, thanks to chemically modified and biocompatible nanosensors, they were able to study individual proteins to determine their tertiary structure and dynamics of cell receptors, for example? That would be a pharmacist’s dream come true, especially as six out of ten drugs target cell receptors through which the drugs produce their beneficial effect.Proteins that are integral and stabilizing components of the cell membrane cannot be isolated from the latter, at least not at the moment. However, if pharmaceutical researchers knew the structure of individual membrane receptors, they would be able to find out how a certain receptor reacts to a specific molecule. They would potentially be able to produce drugs that target specific receptors on the basis of the receptors’ specific intracellular signals and molecular dynamics. Conversely, this knowledge would help pharmaceutical companies save money that would otherwise be spent on expensive research, especially if a specific class of molecules was not required for this purpose.
Although over the next ten to 15 years the ZQB will specifically focus on research into the basic mechanisms of quantum mechanical phenomena, the researchers’ work does not exclude the practical application of the results. Recent research carried out by Plenio and some of his colleagues led to an unexpected discovery. The researchers have since patented the discovery and will establish a start-up company that will combine nanodiamonds and MRI to improve and make molecular imaging used in clinical research and in the long term also in medical diagnostics more effective.In the meantime, Martin Plenio, Prof. Fedor Jelezko, Prof. Tanja Weil and electron microscope specialist Prof. Ute Kaiser from Ulm have shown what the ZQB is all about: they have developed a method to detect ferritin, a protein that contains a large number of magnetic iron ions, directly and quickly. The method involves the use of nanodiamonds that were modified in such a way that they are able to detect the magnetic field generated by the ferritin iron atoms. The method enables an earlier and more accurate detection of illnesses than has previously been possible. The researchers’ theoretical model is very much consistent with the experimental data, thus demonstrating that the method is suitable as a novel protein sensing technology.
Selection of topic-related life sciences papers:Huelga SF and Plenio MB. Vibrations, Quanta and Biology. Contemp Phys 2013; 54: 181-207.Ermakova A, Pramanik G, Cai J-M, Algara-Siller G, Kaiser U, Weil T, Tzeng Y-K, Chang HC, McGuinness LP, Plenio MB, Naydenov B, Jelezko F. Detection of a Few Metallo-Protein Molecules Using Color Centers in Nanodiamonds. Nano Lett 2013; 13 (7): 3305-9 (DOI: 10.1021/nl4015233).