Kirstine Berg-Sørensen is an Associate Professor at the Department of Health Technology at the Technical University of Denmark (DTU).

Congratulations on receiving a Novo Nordisk Foundation, NERD program grant for your project!

Please tell us about your research and why is it important.

In general terms, my research deals with mechanical properties of biological matter, mainly single cells, and development of methods to study it. As it appears, it is a highly interdisciplinary research field and I believe that there is much to be gained from such interaction between different expertise and mindsets. In my NERD project, my team and I will, with our collaborators, measure intracellular temperature variations as well as intracellular mechanical properties. The intracellular thermometer is a nanoscale diamond crystal with a particular defect, a nitrogen-vacancy (NV) center that can be address by light and microwaves. It turns out that the energy levels of the NV center depend on both magnetic fields and temperature and by clever design of a measurement protocol, it can be used either as a magnetometer or as a thermometer. For the cell types, we investigate, no magnetic field effects are expected, but we speculate that metabolic activity of the cell is linked to temperature differences. In addition, the nanodiamonds will act as probe particles in an optical trap, and we plan to move the nanodiamonds to specific positions inside the cell by use of the optical trap and carry out the temperature measurement there. Simultaneously, we can observe stochastic motion of the nanodiamond within the optical trap and extract the mechanical characteristics of the cell cytoplasm which surrounds the trapped nanodiamond from our observations.

In literature, ability to measure NMR spectra by interaction of nuclei with the electrons in NV centers in diamond have been demonstrated, and with the 7 year NERD program, I will have the opportunity to explore if and how we can use NV centers in intracellular nanodiamonds for intracellular NMR spectroscopy. Maybe we will even be able to link mechanical properties of the cell to particular molecules in the cell.

What are your plans and what are the possibilities that this grant opens for you?

It is clear that a grant of this duration gives me the opportunity to dare a more risky research project.

Where have you studied and which positions have you held before your current one?

I studied physics and chemistry at Aarhus University, where I also carried out my Ph.D. studies, on laser cooling of atoms and later cold, dilute atomic gases. This led me to do a postdoc at the Rowland Institute for Science (now associated with Harvard University), then a postdoc at University of Copenhagen, a fellowship at NORDITA and assistant and associate professor positions at the Niels Bohr Institute, on “soft money”. During the time, I changed field to biological physics in particular as I obtained a grant from the FREJA program back in 1999, to initiate the optical tweezers group at the Niels Bohr Institute together with Lene Oddershede. In 2005, I moved to DTU Physics as associate professor in biological physics, and in 2020 was transferred to DTU Health Technology, where my new research project fits well into the research themes.

How did you choose the field of physics you are now specialized in?

In 1997, I attended a Nobel Prize seminar in Stockholm, held prior to awarding the Nobel Prize in Physics to Steven Chu, Claude Cohen-Tannoudji and William D. Phillips for their work on laser cooling of atoms. In that seminar, Thomas T. Perkins, who was a Ph.D. student of Steven Chu, presented his work using optical tweezers to manipulate DNA molecules. I was sold – I guess because of the interdisciplinary aspect. A year later, the opportunity to apply for a FREJA grant came forward and I teamed up with Lene Oddershede and Sonia Grego to apply for the program, and to introduce optical trapping in Denmark.

What motivated you to study physics?

To be honest, when I started studying, I had imagined that I would major in chemistry. However, the more rigorous and mathematical approach in physics soon appealed to me.

Did you have a role model or mentor? If so, what inspiration did you get from them?

No, not really. When I was younger, I benefitted from the discussions within KIF – KIF was started when I was a student.

What advice would you give to young people (in particular women and minorities) who would like to pursue a career in science?

To find a mentor and to learn to say no to tasks which do not really count on your CV.