Studying a very small and unknown part of the human body

Jacob Croft studies flagella, the lash-like appendage that some cells use for locomotion. Sperm have flagella. Flagella contain microtubules that are tube-shaped proteins that provide stability and the ability to move. Green alga or trypanosomes, single cell creatures that cause sleeping sickness, are often used as model organisms. Jacob Croft, however, uses human sperm since he is more interested in how humans work. In humans, the tip of the flagella also has a spiral structure in the microtubules. The spiral is not found in other species, and he wants to understand what its function is.

“I also want to identify the protein that makes the spiral. It is very exciting since it is part of the human body that is completely unknown. The problem is that it is difficult to isolate just the tip.”

Thousands of images creates a three-dimensional image of the cell

That’s where the microscope comes in. Or more accurately, a cryo-electron microscope. He uses it to look at compounds that he has first frozen using liquid ethane. It is important to freeze the compounds quickly, otherwise ice crystals form and damage the cells.

“With the help of computer power to combine several thousand pictures from different angles, you get a picture where you can see the positions of the atoms in relation to each other in the microtubules and in the spiral. Several of these pictures are then combined into a three-dimensional image that can be rotated and looked at from different angles on a computer. The resolution is sufficient to be able to identify individual amino acids. If I can produce a sequence of at least ten amino acids, though preferably more, I can match them against a list of hundreds of possible proteins and in this way hopefully determine which protein it is.

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Jacob Croft did his bachelor’s degree at the University of Arizona, and an exchange programme allowed him to study one semester at Uppsala University. He then applied for doctoral positions both in the U.S. and in Gothenburg. Since he enjoys working with electron microscopy, he was happy to receive the position at the Department of Chemistry and Molecular Biology at the University of Gothenburg. He has now been in Gothenburg for nearly two years. He likes Sweden and Gothenburg.

“People here are more similar to me than people in the United States. Swedes are more focused on helping each other; its’s not just about ‘me first’.”

Climbs in his spare time

He thinks Gothenburg is a good-sized city that is easy to get around in since the public transportation is so good. Another advantage is the opportunities for climbing near by. As a doctoral student, it can be difficult to find a balance with everything you want to do, but he does try to take time off on the weekends and climbing is a good way to relax.

“I've always liked to be physically active. When you climb, you are competing with yourself. It involves problem solving, where you have to figure out the best way to tackle the rock face. You also get to be out outdoors and it is easy to make friends.”

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