MICROSCOPY & IMAGING
LIGHTIN THE DARK
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Switchable proteins for biomedical imaging
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iomedical imaging is the window through which we can look into organisms. It allows us to see cells, their behaviour and localisation that
would otherwise be hidden. Tracking very few cells over time without damaging them is a key challenge in health research. For this purpose, Helmholtz Munich researchers engineer natural tools: switchable proteins. In the interview below, Andre C. Stiel, who is leading the group for Cell Engineering at the Institute of Biological and Medical Imaging at Helmholtz Munich, talks about their potential for biomedical imaging, his latest study and the challenges of the future.
HOW DO PROTEINS HELP IN BIOMEDICAL IMAGING? Stiel says that “proteins are molecules made out of amino acids. In our bodies and in all life forms, proteins have many functions – for example they are the machinery that allows the cells to generate energy or
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receive information. In imaging, we can utilise proteins that generate signals, for example light, to observe what is happening within a live organism. “Proteins have the advantage that they are genetically encoded, they can become a component of the cell or the organism – in contrast to, for example, a dye that needs to be added from the outside. In imaging we can use this for something we call labelling. Labels open up exciting possibilities for tracking cells in different states over a long period of time and without having to interfere or damage the living tissue. Tis allows us, for example, to study a disease or treatment in a relatively natural way and thus to understand diseases better.”
WHAT’S THE SECRET OF THE SWITCHABLE PROTEINS THAT YOU ENGINEER? “Switchable label proteins can change their state, in our case the signal that
we read out, upon illumination with different colours of light,” states Stiel. “Te molecular mechanism acts like a tiny switch that changes the state of the protein from on to off and with that the signal it generates. In nature, those proteins are often responsible for light dependent responses – for example of plants orienting towards the light.” Stiel uses switchable proteins in a method called optoacoustic imaging. When asked to describe what that is, he says that, “Optoacoustic imaging – where world-leading research is done at Helmholtz Munich by Vasilis Ntziachristos – is an imaging method that relies on reading out ultrasound signal generated by light. Optoacoustic imaging already has the power to deliver a combination of higher penetration depth, a higher resolution and larger fields of view than other imaging technologies. However, for many research
Model of a switchable sensor
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