Get to know the board: Loes Kroon-Batenburg

I am working in crystallography for over 40 years. I came to our lab (Laboratorium voor Kristalchemie) in 1977 as a student and worked on solving carbohydrate crystal structures with Jan Kanters. We continued this work in my PhD (1980-1985, Prof. A.F Peerdeman), when I got also interested in modelling, both with quantum chemical methods and molecular mechanics/dynamics. After my PhD, I continued working on carbohydrates and in particular on cellulose, derivatives and wood fibers with my husband Jan Kroon (then the professor of our group), with whom I did many projects financed by industry (AkzoNobel), Economic Affairs (IOP-K and EET), EU-FAIR and STW (Fig. a&b). I was a post-doc during more than 15 years (impossible these days!), but I did not mind: we were always successful in getting grants for interesting projects and I was very happy to stay with Jan in his lab. That situation changed completely when Jan died unexpectedly in 2001. Piet Gros took over the lead of the group who already transformed it into a protein crystallography lab.  I was appointed assistant professor, not without the help of the dean of chemistry, Prof. J.F.G Vliegenthart, in 2003. My research changed to methods developments in data processing, an area that I already became interested in because of my work on fiber diffraction. More recently, I became interested in diffuse scattering in both chemical and macromolecular crystallography (Fig. c). I have been active in the Diffraction Data Deposition Working Group (DDDWG) of the IUCr (International Union of Crystallography) from 2011 onward, and which now turned into a standing committee CommDat. We are setting up a new section in IUCrData: the Raw Data Letter, with the aim describing interesting, unusual, intriguing or complicated diffraction data, that could be a challenge for methods or software developers, but also for creating visibility of the data, which should be deposited in an archive with a persistent identifier (e.g. a DOI). More news on this will follow in future News Letters.

a&b) Fibre diffraction pattern of regenerated cellulose yarn (Cordenka EHM) and the crystal structure. c) Diffuse scattering in the hk0 plane of Cyclophilin A crystals.

Get to know the members: Daan Swarts

My name is Daan Swarts, and since 2019 I am an assistant professor at Wageningen University in the Laboratory of Biochemistry. In my independent research group, we focus on the characterization of bacterial immune systems. Also bacteria can get ‘sick’: invading nucleic acids such as viruses (bacteriophages) can kill cells, and other mobile genetic elements such as plasmids and transposons can be a metabolic burden or reduce fitness. Bacterial immune systems protect their host against such mobile genetic elements. Well-known examples of such systems are restriction-modification systems and CRISPR-Cas, but our research focuses on distinct immune systems of which the evolution, functionality, mechanisms, and structures are unknown. We are mainly interested in these systems from a fundamental point of view, but if interesting systems are found they might be repurposed for DNA editing or detection.

During my PhD (performed in the group of Prof. dr. John van der Oost at Wageningen University) my interest in bacterial immune systems was raised: I focused on the characterization of prokarytic Argonaute proteins (pAgos), which are homologous to eukaryotic Argonaute proteins (the key enzyme in RNA silencing pathways). We uncovered that pAgos interfere not with RNA but with DNA, and can protect their against invading DNA. During my PhD I got interested in protein structures, and wanted to learn how to apply structural biology methods. I continued my research as a post-doctoral EMBO fellow in the group of Prof. dr. Martin Jinek at the University of Zurich. There, my research revolved around determination of the structure and mechanisms of CRISPR-Cas12a, a CRISPR effector enzyme with capacities similar to that of Cas9. I learned how to apply X-ray crystallography and interpret structures, which remains important in the research we currently perform in my research group.

Daan Swarts’ lab, April 2022

We investigate prokaryotic immune systems using research techniques from various fields including bacterial genetics and biochemistry. X-ray crystallography is used to determine the macromolecular structures of proteins in complex with the nucleic acids that they interact with. Combined, this allows us to chart in detail the function and biochemical mechanisms of uncharacterized prokaryotic immune systems. Funded by a VENI, an ERC starting grant, and some independent PhD grants, my team currently consists of six PhD students and a technician. We recently published the first research paper from my group, in which we characterized an Argonaute-based immune system that kills its host to prevent spread to other bacteria (sorry no structures (yet…)).

In my free time (as far as that exists next to the tenure track), I like to spend time with my family (my girlfriend and I have a daughter (4y) and a son (1y)), travel, be outside in nature, or play (board)games with friends. I also go to the gym and play field hockey to relieve pressure. During the corona pandemic, I also picked up gardening as a hobby. I am looking forward to meet researchers in the Dutch crystallography field in person, now this is possible again!