Searching for quantum physics in all the right places

Searching for quantum physics in all the right placesA ‘quantum witness’ plot of the quantum state of a biological pigment–protein complex—the FMO complex from green sulfur bacteria. Positive values (blue to red) indicate that the system’s dynamics cannot be described classically, indicating that it is in a quantum state.

An improved method for measuring quantum properties offers new insight into the unique characteristics of quantum systems.

The properties of  physical systems are fundamentally different to those of classical systems in a way that makes them attractive for applications such as computing and communications. However, it is often difficult to determine whether a system is in a quantum or classical physical state. Franco Nori and colleagues from the RIKEN Center for Emergent Matter Science, together with collaborators in Taiwan, have now developed a mechanism that permits the reliable detection of —even in complex systems1.

The unique behavior of quantum states arises from the  of different states—a property known as quantum coherence. The physicist Erwin Schrödinger famously compared the concept of quantum coherence to a theoretical experiment in which a cat is sealed in a box with a vial of poison to be released by a random quantum mechanism. Without looking inside the box, it cannot be known whether the cat is dead or alive; the cat is therefore in a quantum coherent state. While some quantum states are used for computing, they also occur in nature—in certain , for example.

Measuring the properties of  is important to further their technological utility. Unfortunately, existing measurement methods are impractical due to their complexity and the constraints they place on the quantum states that can be detected.

“Our main goal was to devise an unambiguous test that is easy and practical to implement, and which relies on as little ‘foreknowledge’ of the system as possible, to determine its quantum properties,” explains Neill Lambert, a member of the research team.

The detection scheme developed by Nori, Lambert and colleagues involves the introduction of two ‘quantum witnesses’ that allow the comparison of two runs of an experiment: one in which the state of a system is observed twice, and one where it is only observed once. This procedure effectively sums the results of multiple random experiments to test whether there is any deviation from the expected classical values, which would provide evidence for a  (Fig. 1). For Schrödinger’s cat, such a deviation would suggest that the cat is neither dead nor alive but is instead in a quantum combination of both states.

Among the many possible quantum systems to which this method could be applied, experiments involving biological molecules are particularly interesting, says Nori. “The question of whether quantum coherence exists in biological organisms, for example in a photosynthetic complex, has triggered a surge of interest into the relationship between  and biological function.”

Molecular discovery puts cancer treatment in a new perspective

Researchers from the University of Copenhagen and the National Institutes of Health have obtained ground-breaking new knowledge about proteases – important enzymes which, among other things, play a role in the development of cancer cells. The findings may be significant for the development of cancer drugs, and have just been published in Journal of Biological Chemistry. Cancer cells can exploit an over-production of proteases to force their way into the body.

In a joint effort with the National Institutes of Health, a group of researchers from the University of Copenhagen have taken a step closer to being able to design a more effective anticancer treatment by mapping a previously unknown .

The group has been working with proteases, important enzymes which are responsible for maintaining different  in the body while also being involved in many -diseases, including cancer. Cancer cells can exploit an over-production of proteases to force their way into the body so they can quickly grow and create a space for themselves in which to spread.

“So far, we have been unable to treat cancer patients with drugs which can effectively stop  from spreading, but having now discovered that an important function of proteases has been overlooked, we have the possibility of designing . So far,  have primarily been shaped to stop the proteases from cleaving and thereby activating processes, but this is probably insufficient. Surprisingly, our studies show that proteases perform another function in addition to cleaving; they are also able to bind to one another, besides from cleaving, and kick-starting various ,” says Stine Friis, a postdoc at the Department of Cellular and Molecular Medicine at the University of Copenhagen. She has spearheaded the new research in collaboration with the National Institutes of Health.

Overlooked functions for proteases

One example of proteases making a positive difference is in connection with wound healing. When tissue is damaged, a molecular mechanism starts whereby a protease cleaves and activates the next protease, which then cleaves and activates a third protease, and so on. In other words, it sets off a repair mechanism – a kind of domino effect whereby a single protease can issue a small signal to a whole string of proteases. However, this mechanism can also be exploited by cancer cells, enabling them to spread.

“My generation of molecular biologists learned that proteases are enzymes which are capable of cleaving and activating other proteases, and that this molecular mechanism – called proteolysis – is their sole function. However, our new research findings show that proteases have functions which until now have been overlooked. Yet the key to designing effective drugs is to understand all the molecular mechanisms that make the cancer grow,” says Stine Friis.

Bind instead of cleave

More specifically, the research group has worked with two proteases, matriptase and prostasin, which are both essential for maintaining healthy cells in the skin, intestines and other organs. However, in contrast to what has so far been believed, the two proteases do not activate one another by one cleaving the next, i.e. through proteolysis. In fact, prostasin’s role in activating matriptase is surprisingly independent of this mechanism. Instead of cleaving one another, the two proteases bind to each other, which is most unusual, and thereby start important processes.

Through knowing about this previously overseen but vital function of how proteases activate the cell’s signals, researchers hope to improve our understanding of how proteases operate in the body. And not just in normal circumstances, but also in situations where something malfunctions with the protease balance, such as in cancer.

“Hopefully our new findings will inspire others to think outside the box, opening the doors to innovation with drugs aimed at regulating protease activity, such as anticancer drugs. The drugs we design today are developed to halt the cleaving process, but even though it is stopped, some proteases can apparently continue to transmit signals by binding to instead of cleaving one another. If we can stop the binding, we should be able to develop better drugs, which in the long term will bring us closer to developing successful cancer treatments. If you only understand how one half of an engine functions, it’s almost impossible to repair it,” says Stine Friis.

About proteases

Proteases are important enzymes which, among other things, play a role in the development of cancer cells. The proteases in our bodies are active all the time. In connection with wound healing, the process of proteolysis is initiated to repair the damaged tissue.

Proteolysis is the molecular mechanism whereby a protease cleaves and activates the next protease, which then cleaves and activates a third protease, and so on. The mechanism is a kind of domino effect, whereby a single protease can issue a little signal to a whole string of proteases.

It is important to have balanced protease levels – when they are out of balance and there is too much of them, things go wrong.

Researchers have produced models of mice with excessive levels of the proteases matriptase and prostasin, and those mice with too much protease develop a predisposition to skin cancer. The mice are used to study proteolysis.

Cancer does not necessarily develop in all cases where the mice have excessive  levels, but when it specifically involves matriptase and prostasin, it does. Previous research has also shown that  have raised matriptase levels.

Novel bacterial 'language' discovered

Novel bacterial 'language' discovered

LMU researchers have identified a yet unknown bacterial cell-cell.

In nature, bacteria are no mavericks but live in close association with neighboring bacteria. They have evolved specific cell- systems that allow them to detect the presence of others and even to build up cooperative networks.

LMU microbiologist PD Dr. Ralf Heermann and Professor Helge Bode of the Goethe-University in Frankfurt have just reported the discovery of a previously unknown bacterial “language”. Their findings are detailed in the latest issue of the journal Nature Chemical Biology. “Our results demonstrate that bacterial communication is much more complex than has been assumed to date,” Heermann says.

The bacterial  that is currently best understood uses N-acylhomoserine lactones (AHLs) as signals. These compounds are made by enzymes that belong to the group of LuxI-family synthases. Transmitting cells secrete the signal and neighboring cells recognize the concentration via a LuxR-type receptor. Signal perception changes the pattern of  in the receiving cells, which results in alterations in their functional properties or behavior. However, many bacteria have LuxR receptors but lack any LuxI homolog, so that they cannot produce AHLs. These receptors are referred to as LuxR solos.

A new class of bacterial signaling molecules

Ralf Heermann and Helge Bode have now discovered a type of ligand that binds to LuxR solos. As , they chose the species Photorhabdus luminescens, a  that is lethal to insects.

Novel bacterial 'language' discovered
Bacteria communicate by means of chemical processes. LMU microbiologist PD Dr. Ralf Heermann and Professor Helge Bode of the Goethe-University Frankfurt have identified a novel bacterial cell-cell communication system that uses alpha-pyrones …more

“We have identified a new class of bacterial signaling molecules, which are produced by a previously unknown biochemical route,” explains Helge Bode, Merck Professor of Molecular Biotechnology at Goethe-Universität Frankfurt. It turns out that a LuxR solo of this bacterium responds to compounds called alpha-pyrones, specifically to photopyrones. Furthermore, the researchers have identified the pyrone synthase (PpyS) that catalyzes the biosynthesis of photopyrones. The pyrone-based signaling system allows the bacteria to recognize one another, whereupon they produce a surface factor that causes cell clumping. Heermann and Bode assume that this collective behavior makes the cells less vulnerable to the insect’s innate immune system, and then allows them to kill their victims by the production of various of toxins.” P. luminescens is a useful model organism, because it is related to many human pathogens, including coliform bacteria such as enterohemorrhagic E. coli (EHEC) and well as plague bacteria,” Heermann points out.