I have another photo-op here. Today I'm working on oxygen measurements with a membrane inlet mass spectrometer (MIMS) in Todd Kana's lab at the University of Maryland. Dissolved gasses (oxygen and nitrogen) come out of solution and cross a membrane into a vacuum chamber where they flow into the mass spectrometer. The mass spectrometer separates the molecules using magnets and so figure out if a molecule of oxygen or nitrogen is hitting a detector.
We are using this instrument to investigate the amount of oxygen used and produced in photosynthesis in
Prochlorococcus (
Prochlorococcus is our organism of interest - see page on the Astrobiology project for more info). While there is a great deal of literature on what molecules are upregulated in high light for
Prochlorococcus, we are interested in photosynthetic behavior of this organism in different light conditions. This kind of work, along with carbon fixation and fluorescence measurements, is important for predicting how an organism will behave (photosynthesize) in a variety of light conditions.
The MIMS instrument uses oxygen isotope ratios to look at both the amount of oxygen used and the amount produced in photosynthesis, so we add an isotope of oxygen not found in air (18-O
2). I'm not going to explain how this works in detail, but just want to put up a picture of the screen output. The green and white dots below are isotope ratios of importance (16-O2:nitrogen and 18-O2:nitrogen respectively). This screen shows that 18-O2 is decreasing rapidly (white) while 16-O2 is beginning to decline (green) relative to the flux of nitrogen through the membrane (which should be mostly constant). (Yellow is nitrogen, blue and red are 18-O2 and 16-O2).
